// Copyright Epic Games, Inc. All Rights Reserved.

#include "DerivedDataBackendInterface.h"

#if WITH_HTTP_DDC_BACKEND

#if PLATFORM_WINDOWS || PLATFORM_HOLOLENS
#include "Windows/WindowsHWrapper.h"
#include "Windows/AllowWindowsPlatformTypes.h"
#endif
#include "curl/curl.h"
#if PLATFORM_WINDOWS || PLATFORM_HOLOLENS
#include "Windows/HideWindowsPlatformTypes.h"
#endif
#include "Algo/Accumulate.h"
#include "Algo/Find.h"
#include "Algo/Transform.h"
#include "Compression/CompressedBuffer.h"
#include "Containers/StaticArray.h"
#include "Containers/StringView.h"
#include "Containers/Ticker.h"
#include "DerivedDataCacheKey.h"
#include "DerivedDataCachePrivate.h"
#include "DerivedDataCacheRecord.h"
#include "DerivedDataCacheUsageStats.h"
#include "DerivedDataChunk.h"
#include "DerivedDataValue.h"
#include "Dom/JsonObject.h"
#include "Experimental/Containers/FAAArrayQueue.h"
#include "GenericPlatform/GenericPlatformFile.h"
#include "HAL/PlatformFileManager.h"
#include "IO/IoHash.h"
#include "Memory/SharedBuffer.h"
#include "Misc/FileHelper.h"
#include "Misc/ScopeLock.h"
#include "Misc/SecureHash.h"
#include "Misc/StringBuilder.h"
#include "Policies/CondensedJsonPrintPolicy.h"
#include "ProfilingDebugging/CountersTrace.h"
#include "ProfilingDebugging/CpuProfilerTrace.h"
#include "Serialization/BufferArchive.h"
#include "Serialization/CompactBinary.h"
#include "Serialization/CompactBinaryPackage.h"
#include "Serialization/CompactBinaryValidation.h"
#include "Serialization/CompactBinaryWriter.h"
#include "Serialization/JsonReader.h"
#include "Serialization/JsonSerializer.h"
#include "Serialization/JsonWriter.h"

#if WITH_SSL
#include "Ssl.h"
#include <openssl/ssl.h>
#endif

// Enables data request helpers that internally
// batch requests to reduce the number of concurrent
// connections.
#ifndef WITH_DATAREQUEST_HELPER
	#define WITH_DATAREQUEST_HELPER 1
#endif

#define UE_HTTPDDC_BACKEND_WAIT_INTERVAL 0.01f
#define UE_HTTPDDC_BACKEND_WAIT_INTERVAL_MS ((uint32)(UE_HTTPDDC_BACKEND_WAIT_INTERVAL*1000))
#define UE_HTTPDDC_HTTP_REQUEST_TIMEOUT_SECONDS 30L
#define UE_HTTPDDC_HTTP_REQUEST_TIMEOUT_ENABLED 1
#define UE_HTTPDDC_HTTP_DEBUG 0
#define UE_HTTPDDC_GET_REQUEST_POOL_SIZE 48
#define UE_HTTPDDC_PUT_REQUEST_POOL_SIZE 16
#define UE_HTTPDDC_MAX_FAILED_LOGIN_ATTEMPTS 16
#define UE_HTTPDDC_MAX_ATTEMPTS 4
#define UE_HTTPDDC_MAX_BUFFER_RESERVE 104857600u
#define UE_HTTPDDC_BATCH_SIZE 12
#define UE_HTTPDDC_BATCH_NUM 64
#define UE_HTTPDDC_BATCH_GET_WEIGHT 4
#define UE_HTTPDDC_BATCH_HEAD_WEIGHT 1
#define UE_HTTPDDC_BATCH_WEIGHT_HINT 12

namespace UE::DerivedData
{

TRACE_DECLARE_INT_COUNTER(HttpDDC_Exist, TEXT("HttpDDC Exist"));
TRACE_DECLARE_INT_COUNTER(HttpDDC_ExistHit, TEXT("HttpDDC Exist Hit"));
TRACE_DECLARE_INT_COUNTER(HttpDDC_Get, TEXT("HttpDDC Get"));
TRACE_DECLARE_INT_COUNTER(HttpDDC_GetHit, TEXT("HttpDDC Get Hit"));
TRACE_DECLARE_INT_COUNTER(HttpDDC_Put, TEXT("HttpDDC Put"));
TRACE_DECLARE_INT_COUNTER(HttpDDC_PutHit, TEXT("HttpDDC Put Hit"));
TRACE_DECLARE_INT_COUNTER(HttpDDC_BytesReceived, TEXT("HttpDDC Bytes Received"));
TRACE_DECLARE_INT_COUNTER(HttpDDC_BytesSent, TEXT("HttpDDC Bytes Sent"));

static CURLcode sslctx_function(CURL * curl, void * sslctx, void * parm);

typedef TSharedPtr<class IHttpRequest> FHttpRequestPtr;
typedef TSharedPtr<class IHttpResponse, ESPMode::ThreadSafe> FHttpResponsePtr;

/**
 * Encapsulation for access token shared by all requests.
 */
struct FHttpAccessToken
{
public:
	FHttpAccessToken() = default;
	FString GetHeader();
	void SetHeader(const TCHAR*);
	uint32 GetSerial() const;
private:
	FRWLock		Lock;
	FString		Token;
	uint32		Serial;
};

struct FHttpSharedData
{
	FHttpSharedData()
	{
		FMemory::Memset(WriteLocked, 0, sizeof(WriteLocked));
		CurlShare = curl_share_init();
		curl_share_setopt(CurlShare, CURLSHOPT_USERDATA, this);
		curl_share_setopt(CurlShare, CURLSHOPT_LOCKFUNC, LockFn);
		curl_share_setopt(CurlShare, CURLSHOPT_UNLOCKFUNC, UnlockFn);
		curl_share_setopt(CurlShare, CURLSHOPT_SHARE, CURL_LOCK_DATA_DNS);
		curl_share_setopt(CurlShare, CURLSHOPT_SHARE, CURL_LOCK_DATA_SSL_SESSION);
	}

	~FHttpSharedData()
	{
		curl_share_cleanup(CurlShare);
	}

	CURLSH* CurlShare;

private:
	FRWLock Locks[CURL_LOCK_DATA_LAST];
	bool WriteLocked[CURL_LOCK_DATA_LAST];

	static void LockFn(CURL* Handle, curl_lock_data Data, curl_lock_access Access, void* User)
	{
		FHttpSharedData* SharedData = (FHttpSharedData*)User;
		if (Access == CURL_LOCK_ACCESS_SHARED)
		{
			SharedData->Locks[Data].ReadLock();
		}
		else
		{
			SharedData->Locks[Data].WriteLock();
			SharedData->WriteLocked[Data] = true;
		}
	}
	static void UnlockFn(CURL* Handle, curl_lock_data Data, void* User)
	{
		FHttpSharedData* SharedData = (FHttpSharedData*)User;
		if (!SharedData->WriteLocked[Data])
		{
			SharedData->Locks[Data].ReadUnlock();
		}
		else
		{
			SharedData->WriteLocked[Data] = false;
			SharedData->Locks[Data].WriteUnlock();
		}
	}
};

/**
 * Minimal HTTP request type wrapping CURL without the need for managers. This request
 * is written to allow reuse of request objects, in order to allow connections to be reused.
 *
 * CURL has a global library initialization (curl_global_init). We rely on this happening in 
 * the Online/HTTP library which is a dependency on this module.
 */
class FHttpRequest
{
public:
	/**
	 * Supported request verbs
	 */
	enum RequestVerb
	{
		Get,
		Put,
		PutCompactBinary,
		PutCompressedBlob,
		Post,
		PostJson,
		Delete,
		Head
	};

	/**
	 * Convenience result type interpreted from HTTP response code.
	 */
	enum Result
	{
		Success,
		Failed,
		FailedTimeout
	};

	FHttpRequest(const TCHAR* InDomain, const TCHAR* InEffectiveDomain, FHttpAccessToken* InAuthorizationToken, bool bInLogErrors)
		: bLogErrors(bInLogErrors)
		, Domain(InDomain)
		, EffectiveDomain(InEffectiveDomain)
		, AuthorizationToken(InAuthorizationToken)
	{
		Curl = curl_easy_init();
		Reset();
	}

	~FHttpRequest()
	{
		curl_easy_cleanup(Curl);
	}

	/**
	 * Resets all options on the request except those that should always be set.
	 */
	void Reset()
	{
		Headers.Reset();
		ResponseHeader.Reset();
		ResponseBuffer.Reset();
		ResponseCode = 0;
		ReadDataView = TArrayView<const uint8>();
		WriteDataBufferPtr = nullptr;
		WriteHeaderBufferPtr = nullptr;
		BytesSent = 0;
		BytesReceived = 0;
		CurlResult = CURL_LAST;

		static FHttpSharedData SharedData;

		curl_easy_reset(Curl);

		// Options that are always set for all connections.
#if UE_HTTPDDC_HTTP_REQUEST_TIMEOUT_ENABLED
		curl_easy_setopt(Curl, CURLOPT_CONNECTTIMEOUT, UE_HTTPDDC_HTTP_REQUEST_TIMEOUT_SECONDS);
#endif
		curl_easy_setopt(Curl, CURLOPT_FOLLOWLOCATION, 1L);
		curl_easy_setopt(Curl, CURLOPT_NOSIGNAL, 1L);
		curl_easy_setopt(Curl, CURLOPT_DNS_CACHE_TIMEOUT, 300L); // Don't re-resolve every minute
		curl_easy_setopt(Curl, CURLOPT_SHARE, SharedData.CurlShare);
		// SSL options
		curl_easy_setopt(Curl, CURLOPT_USE_SSL, CURLUSESSL_ALL);
		curl_easy_setopt(Curl, CURLOPT_SSL_VERIFYPEER, 1);
		curl_easy_setopt(Curl, CURLOPT_SSL_VERIFYHOST, 1);
		curl_easy_setopt(Curl, CURLOPT_SSLCERTTYPE, "PEM");
		// Response functions
		curl_easy_setopt(Curl, CURLOPT_HEADERDATA, this);
		curl_easy_setopt(Curl, CURLOPT_HEADERFUNCTION, &FHttpRequest::StaticWriteHeaderFn);
		curl_easy_setopt(Curl, CURLOPT_WRITEDATA, this);
		curl_easy_setopt(Curl, CURLOPT_WRITEFUNCTION, StaticWriteBodyFn);
		// SSL certification verification
		curl_easy_setopt(Curl, CURLOPT_CAINFO, nullptr);
		curl_easy_setopt(Curl, CURLOPT_SSL_CTX_FUNCTION, *sslctx_function);
		curl_easy_setopt(Curl, CURLOPT_SSL_CTX_DATA, this);
		// Allow compressed data
		curl_easy_setopt(Curl, CURLOPT_ACCEPT_ENCODING, "gzip");
		// Rewind method, handle special error case where request need to rewind data stream
		curl_easy_setopt(Curl, CURLOPT_SEEKFUNCTION, StaticSeekFn);
		curl_easy_setopt(Curl, CURLOPT_SEEKDATA, this);
		// Set minimum speed behavior to allow operations to abort if the transfer speed is poor for the given duration (1kbps over a 30 second span)
		curl_easy_setopt(Curl, CURLOPT_LOW_SPEED_TIME, 30L);
		curl_easy_setopt(Curl, CURLOPT_LOW_SPEED_LIMIT, 1024L);
		// Debug hooks
#if UE_HTTPDDC_HTTP_DEBUG
		curl_easy_setopt(Curl, CURLOPT_DEBUGDATA, this);
		curl_easy_setopt(Curl, CURLOPT_DEBUGFUNCTION, StaticDebugCallback);
		curl_easy_setopt(Curl, CURLOPT_VERBOSE, 1L);
#endif
	}

	/** Gets the domain name for this request */
	const FString& GetName() const
	{
		return Domain;
	}

	/** Gets the domain name for this request */
	const FString& GetDomain() const
	{
		return Domain;
	}

	/** Gets the effective domain name for this request */
	const FString& GetEffectiveDomain() const
	{
		return EffectiveDomain;
	}

	/** Returns the HTTP response code.*/
	const int64 GetResponseCode() const
	{
		return ResponseCode;
	}

	/** Returns the number of bytes received this request (headers withstanding). */
	const size_t GetBytesReceived() const
	{
		return BytesReceived;
	}

	/** Returns the number of bytes sent during this request (headers withstanding). */
	const size_t  GetBytesSent() const
	{
		return BytesSent;
	}

	/**
	 * Upload buffer using the request, using either "Put" or "Post" verbs.
	 * @param Uri Url to use.
	 * @param Buffer Data to upload
	 * @return Result of the request
	 */
	template<RequestVerb V>
	Result PerformBlockingUpload(const TCHAR* Uri, TArrayView<const uint8> Buffer, TConstArrayView<long> ExpectedErrorCodes = {})
	{
		static_assert(V == Put || V == PutCompactBinary || V == PutCompressedBlob || V == Post || V == PostJson, "Upload should use either Put or Post verbs.");
		
		uint32 ContentLength = 0u;

		if constexpr (V == Put || V == PutCompactBinary || V == PutCompressedBlob)
		{
			curl_easy_setopt(Curl, CURLOPT_UPLOAD, 1L);
			curl_easy_setopt(Curl, CURLOPT_INFILESIZE, Buffer.Num());
			curl_easy_setopt(Curl, CURLOPT_READDATA, this);
			curl_easy_setopt(Curl, CURLOPT_READFUNCTION, StaticReadFn);
			if constexpr (V == PutCompactBinary)
			{
				Headers.Add(FString(TEXT("Content-Type: application/x-ue-cb")));
			}
			else if constexpr (V == PutCompressedBlob)
			{
				Headers.Add(FString(TEXT("Content-Type: application/x-ue-comp")));
			}
			else
			{
				Headers.Add(FString(TEXT("Content-Type: application/octet-stream")));
			}
			ContentLength = Buffer.Num();
			ReadDataView = Buffer;
		}
		else if (V == Post || V == PostJson)
		{
			curl_easy_setopt(Curl, CURLOPT_POST, 1L);
			curl_easy_setopt(Curl, CURLOPT_INFILESIZE, Buffer.Num());
			curl_easy_setopt(Curl, CURLOPT_READDATA, this);
			curl_easy_setopt(Curl, CURLOPT_READFUNCTION, StaticReadFn);
			Headers.Add(V == Post ? FString(TEXT("Content-Type: application/x-www-form-urlencoded")) : FString(TEXT("Content-Type: application/json")));
			ContentLength = Buffer.Num();
			ReadDataView = Buffer;
		}

		return PerformBlocking(Uri, V, ContentLength, ExpectedErrorCodes);
	}

	/**
	 * Download an url into a buffer using the request.
	 * @param Uri Url to use.
	 * @param Buffer Optional buffer where data should be downloaded to. If empty downloaded data will
	 * be stored in an internal buffer and accessed GetResponse* methods.
	 * @return Result of the request
	 */
	Result PerformBlockingDownload(const TCHAR* Uri, TArray<uint8>* Buffer, TConstArrayView<long> ExpectedErrorCodes = {400})
	{
		curl_easy_setopt(Curl, CURLOPT_HTTPGET, 1L);
		WriteDataBufferPtr = Buffer;

		return PerformBlocking(Uri, Get, 0u, ExpectedErrorCodes);
	}

	/**
	 * Query an url using the request. Queries can use either "Head" or "Delete" verbs.
	 * @param Uri Url to use.
	 * @return Result of the request
	 */
	template<RequestVerb V>
	Result PerformBlockingQuery(const TCHAR* Uri, TConstArrayView<long> ExpectedErrorCodes = {400})
	{
		static_assert(V == Head || V == Delete, "Queries should use either Head or Delete verbs.");

		if (V == Delete)
		{
			curl_easy_setopt(Curl, CURLOPT_CUSTOMREQUEST, "DELETE");
		}
		else if (V == Head)
		{
			curl_easy_setopt(Curl, CURLOPT_NOBODY, 1L);
		}

		return PerformBlocking(Uri, V, 0u, ExpectedErrorCodes);
	}

	/**
	 * Set a header to send with the request.
	 */
	void SetHeader(const TCHAR* Header, const TCHAR* Value)
	{
		check(CurlResult == CURL_LAST); // Cannot set header after request is sent
		Headers.Add(FString::Printf(TEXT("%s: %s"), Header, Value));
	}

	/**
	 * Attempts to find the header from the response. Returns false if header is not present.
	 */
	bool GetHeader(const ANSICHAR* Header, FString& OutValue) const
	{
		check(CurlResult != CURL_LAST);  // Cannot query headers before request is sent

		const ANSICHAR* HeadersBuffer = (const ANSICHAR*) ResponseHeader.GetData();
		size_t HeaderLen = strlen(Header);

		// Find the header key in the (ANSI) response buffer. If not found we can exist immediately
		if (const ANSICHAR* Found = strstr(HeadersBuffer, Header))
		{
			const ANSICHAR* Linebreak = strchr(Found, '\r');
			const ANSICHAR* ValueStart = Found + HeaderLen + 2; //colon and space
			const size_t ValueSize = Linebreak - ValueStart;
			FUTF8ToTCHAR TCHARData(ValueStart, ValueSize);
			OutValue = FString(TCHARData.Length(), TCHARData.Get());
			return true;
		}
		return false;
	}

	/**
	 * Returns the response buffer. Note that is the request is performed
	 * with an external buffer as target buffer this string will be empty.
	 */
	const TArray<uint8>& GetResponseBuffer() const
	{
		return ResponseBuffer;
	}

	/**
	 * Returns the response buffer as a string. Note that is the request is performed
	 * with an external buffer as target buffer this string will be empty.
	 */
	FString GetResponseAsString() const
	{
		return GetAnsiBufferAsString(ResponseBuffer);
	}

	/**
	 * Returns the response header as a string.
	 */
	FString GetResponseHeaderAsString()
	{
		return GetAnsiBufferAsString(ResponseHeader);
	}

	/**
	 * Tries to parse the response buffer as a JsonObject. Return empty pointer if 
	 * parse error occurs.
	 */
	TSharedPtr<FJsonObject> GetResponseAsJsonObject() const
	{
		FString Response = GetAnsiBufferAsString(ResponseBuffer);

		TSharedPtr<FJsonObject> JsonObject;
		TSharedRef<TJsonReader<> > JsonReader = TJsonReaderFactory<>::Create(Response);
		if (!FJsonSerializer::Deserialize(JsonReader, JsonObject) || !JsonObject.IsValid())
		{
			return TSharedPtr<FJsonObject>(nullptr);
		}

		return JsonObject;
	}

	/**
	 * Tries to parse the response buffer as a JsonArray. Return empty array if
	 * parse error occurs.
	 */
	TArray<TSharedPtr<FJsonValue>> GetResponseAsJsonArray() const
	{
		FString Response = GetAnsiBufferAsString(ResponseBuffer);

		TArray<TSharedPtr<FJsonValue>> JsonArray;
		TSharedRef<TJsonReader<>> JsonReader = TJsonReaderFactory<>::Create(Response);
		FJsonSerializer::Deserialize(JsonReader, JsonArray);
		return JsonArray;
	}

	/** Will return true if the response code is considered a success */
	static bool IsSuccessResponse(long ResponseCode)
	{
		// We consider anything in the 1XX or 2XX range a success
		return ResponseCode >= 100 && ResponseCode < 300;
	}

private:

	CURL*					Curl;
	CURLcode				CurlResult;
	long					ResponseCode;
	size_t					BytesSent;
	size_t					BytesReceived;
	bool					bLogErrors;

	TArrayView<const uint8>	ReadDataView;
	TArray<uint8>*			WriteDataBufferPtr;
	TArray<uint8>*			WriteHeaderBufferPtr;
	
	TArray<uint8>			ResponseHeader;
	TArray<uint8>			ResponseBuffer;
	TArray<FString>			Headers;
	FString					Domain;
	FString					EffectiveDomain;
	FHttpAccessToken*		AuthorizationToken;

	/**
	 * Performs the request, blocking until finished.
	 * @param Uri Address on the domain to query
	 * @param Verb HTTP verb to use
	 * @param Buffer Optional buffer to directly receive the result of the request.
	 * If unset the response body will be stored in the request.
	 */
	Result PerformBlocking(const TCHAR* Uri, RequestVerb Verb, uint32 ContentLength, TConstArrayView<long> ExpectedErrorCodes)
	{
		static const char* CommonHeaders[] = {
			"User-Agent: Unreal Engine",
			nullptr
		};

		TRACE_CPUPROFILER_EVENT_SCOPE(HttpDDC_CurlPerform);

		// Setup request options
		FString Url = FString::Printf(TEXT("%s/%s"), *EffectiveDomain, Uri);
		curl_easy_setopt(Curl, CURLOPT_URL, TCHAR_TO_ANSI(*Url));

		// Setup response header buffer. If caller has not setup a response data buffer, use internal.
		WriteHeaderBufferPtr = &ResponseHeader;
		if (WriteDataBufferPtr == nullptr)
		{
			WriteDataBufferPtr = &ResponseBuffer;
		}

		// Content-Length should always be set
		Headers.Add(FString::Printf(TEXT("Content-Length: %d"), ContentLength));

		// And auth token if it's set
		if (AuthorizationToken)
		{
			Headers.Add(AuthorizationToken->GetHeader());
		}

		// Build headers list
		curl_slist* CurlHeaders = nullptr;
		// Add common headers
		for (uint8 i = 0; CommonHeaders[i] != nullptr; ++i)
		{
			CurlHeaders = curl_slist_append(CurlHeaders, CommonHeaders[i]);
		}
		// Setup added headers
		for (const FString& Header : Headers)
		{
			CurlHeaders = curl_slist_append(CurlHeaders, TCHAR_TO_ANSI(*Header));
		}
		curl_easy_setopt(Curl, CURLOPT_HTTPHEADER, CurlHeaders);

		// Shots fired!
		CurlResult = curl_easy_perform(Curl);

		// Get response code
		bool bRedirected = false;
		if (CURLE_OK == curl_easy_getinfo(Curl, CURLINFO_RESPONSE_CODE, &ResponseCode))
		{
			bRedirected = (ResponseCode >= 300 && ResponseCode < 400);
		}

		LogResult(CurlResult, Uri, Verb, ExpectedErrorCodes);

		// Clean up
		curl_slist_free_all(CurlHeaders);

		return CurlResult == CURLE_OK ? Success : Failed;
	}

	void LogResult(CURLcode Result, const TCHAR* Uri, RequestVerb Verb, TConstArrayView<long> ExpectedErrorCodes) const
	{
		if (Result == CURLE_OK)
		{
			bool bSuccess = false;
			const TCHAR* VerbStr = nullptr;
			FString AdditionalInfo;

			switch (Verb)
			{
			case Head:
				bSuccess = (ExpectedErrorCodes.Contains(ResponseCode) || IsSuccessResponse(ResponseCode));
				VerbStr = TEXT("querying");
				break;
			case Get:
				bSuccess = (ExpectedErrorCodes.Contains(ResponseCode) || IsSuccessResponse(ResponseCode));
				VerbStr = TEXT("fetching");
				AdditionalInfo = FString::Printf(TEXT("Received: %d bytes."), BytesReceived);
				break;
			case Put:
			case PutCompactBinary:
			case PutCompressedBlob:
				bSuccess = (ExpectedErrorCodes.Contains(ResponseCode) || IsSuccessResponse(ResponseCode));
				VerbStr = TEXT("updating");
				AdditionalInfo = FString::Printf(TEXT("Sent: %d bytes."), BytesSent);
				break;
			case Post:
			case PostJson:
				bSuccess = (ExpectedErrorCodes.Contains(ResponseCode) || IsSuccessResponse(ResponseCode));
				VerbStr = TEXT("posting");
				break;
			case Delete:
				bSuccess = (ExpectedErrorCodes.Contains(ResponseCode) || IsSuccessResponse(ResponseCode));
				VerbStr = TEXT("deleting");
				break;
			}

			if (bSuccess)
			{
				UE_LOG(
					LogDerivedDataCache, 
					Verbose, 
					TEXT("%s: Finished %s HTTP cache entry (response %d) from %s. %s"), 
					*GetName(),
					VerbStr,
					ResponseCode, 
					Uri,
					*AdditionalInfo
				);
			}
			else if(bLogErrors)
			{
				// Print the response body if we got one, otherwise print header.
				FString Response = GetAnsiBufferAsString(ResponseBuffer.Num() > 0 ? ResponseBuffer : ResponseHeader);
				Response.ReplaceCharInline(TEXT('\n'), TEXT(' '));
				Response.ReplaceCharInline(TEXT('\r'), TEXT(' '));
				// Dont log access denied as error, since tokens can expire mid session
				if (ResponseCode == 401)
				{
					UE_LOG(
						LogDerivedDataCache,
						Verbose,
						TEXT("%s: Failed %s HTTP cache entry (response %d) from %s. Response: %s"),
						*GetName(),
						VerbStr,
						ResponseCode,
						Uri,
						*Response
					);
				}
				else
				{ 
					UE_LOG(
						LogDerivedDataCache,
						Display,
						TEXT("%s: Failed %s HTTP cache entry (response %d) from %s. Response: %s"),
						*GetName(),
						VerbStr,
						ResponseCode,
						Uri,
						*Response
					);
				}


			}
		}
		else if(bLogErrors)
		{
			UE_LOG(
				LogDerivedDataCache, 
				Display, 
				TEXT("%s: Error while connecting to %s: %s"), 
				*GetName(),
				*EffectiveDomain,
				ANSI_TO_TCHAR(curl_easy_strerror(Result))
			);
		}
	}

	FString GetAnsiBufferAsString(const TArray<uint8>& Buffer) const
	{
		// Content is NOT null-terminated; we need to specify lengths here
		FUTF8ToTCHAR TCHARData(reinterpret_cast<const ANSICHAR*>(Buffer.GetData()), Buffer.Num());
		return FString(TCHARData.Length(), TCHARData.Get());
	}

	static size_t StaticDebugCallback(CURL * Handle, curl_infotype DebugInfoType, char * DebugInfo, size_t DebugInfoSize, void* UserData)
	{
		FHttpRequest* Request = static_cast<FHttpRequest*>(UserData);

		switch (DebugInfoType)
		{
		case CURLINFO_TEXT:
		{
			// Truncate at 1023 characters. This is just an arbitrary number based on a buffer size seen in
			// the libcurl code.
			DebugInfoSize = FMath::Min(DebugInfoSize, (size_t)1023);

			// Calculate the actual length of the string due to incorrect use of snprintf() in lib/vtls/openssl.c.
			char* FoundNulPtr = (char*)memchr(DebugInfo, 0, DebugInfoSize);
			int CalculatedSize = FoundNulPtr != nullptr ? FoundNulPtr - DebugInfo : DebugInfoSize;

			auto ConvertedString = StringCast<TCHAR>(static_cast<const ANSICHAR*>(DebugInfo), CalculatedSize);
			FString DebugText(ConvertedString.Length(), ConvertedString.Get());
			DebugText.ReplaceInline(TEXT("\n"), TEXT(""), ESearchCase::CaseSensitive);
			DebugText.ReplaceInline(TEXT("\r"), TEXT(""), ESearchCase::CaseSensitive);
			UE_LOG(LogDerivedDataCache, VeryVerbose, TEXT("%s: %p: '%s'"), *Request->GetName(), Request, *DebugText);
		}
		break;

		case CURLINFO_HEADER_IN:
			UE_LOG(LogDerivedDataCache, VeryVerbose, TEXT("%s: %p: Received header (%d bytes)"), *Request->GetName(), Request, DebugInfoSize);
			break;

		case CURLINFO_DATA_IN:
			UE_LOG(LogDerivedDataCache, VeryVerbose, TEXT("%s: %p: Received data (%d bytes)"), *Request->GetName(), Request, DebugInfoSize);
			break;

		case CURLINFO_DATA_OUT:
			UE_LOG(LogDerivedDataCache, VeryVerbose, TEXT("%s: %p: Sent data (%d bytes)"), *Request->GetName(), Request, DebugInfoSize);
			break;

		case CURLINFO_SSL_DATA_IN:
			UE_LOG(LogDerivedDataCache, VeryVerbose, TEXT("%s: %p: Received SSL data (%d bytes)"), *Request->GetName(), Request, DebugInfoSize);
			break;

		case CURLINFO_SSL_DATA_OUT:
			UE_LOG(LogDerivedDataCache, VeryVerbose, TEXT("%s: %p: Sent SSL data (%d bytes)"), *Request->GetName(), Request, DebugInfoSize);
			break;
		}

		return 0;
	}

	static size_t StaticReadFn(void* Ptr, size_t SizeInBlocks, size_t BlockSizeInBytes, void* UserData)
	{
		FHttpRequest* Request = static_cast<FHttpRequest*>(UserData);
		TArrayView<const uint8>& ReadDataView = Request->ReadDataView;

		const size_t Offset = Request->BytesSent;
		const size_t ReadSize = FMath::Min((size_t)ReadDataView.Num() - Offset, SizeInBlocks * BlockSizeInBytes);
		check(ReadDataView.Num() >= Offset + ReadSize);

		FMemory::Memcpy(Ptr, ReadDataView.GetData() + Offset, ReadSize);
		Request->BytesSent += ReadSize;
		return ReadSize;
		
		return 0;
	}

	static size_t StaticWriteHeaderFn(void* Ptr, size_t SizeInBlocks, size_t BlockSizeInBytes, void* UserData)
	{
		FHttpRequest* Request = static_cast<FHttpRequest*>(UserData);
		const size_t WriteSize = SizeInBlocks * BlockSizeInBytes;
		TArray<uint8>* WriteHeaderBufferPtr = Request->WriteHeaderBufferPtr;
		if (WriteHeaderBufferPtr && WriteSize > 0)
		{
			const size_t CurrentBufferLength = WriteHeaderBufferPtr->Num();
			if (CurrentBufferLength > 0)
			{
				// Remove the previous zero termination
				(*WriteHeaderBufferPtr)[CurrentBufferLength-1] = ' ';
			}

			// Write the header
			WriteHeaderBufferPtr->Append((const uint8*)Ptr, WriteSize + 1);
			(*WriteHeaderBufferPtr)[WriteHeaderBufferPtr->Num()-1] = 0; // Zero terminate string
			return WriteSize;
		}
		return 0;
	}

	static size_t StaticWriteBodyFn(void* Ptr, size_t SizeInBlocks, size_t BlockSizeInBytes, void* UserData)
	{
		FHttpRequest* Request = static_cast<FHttpRequest*>(UserData);
		const size_t WriteSize = SizeInBlocks * BlockSizeInBytes;
		TArray<uint8>* WriteDataBufferPtr = Request->WriteDataBufferPtr;

		if (WriteDataBufferPtr && WriteSize > 0)
		{
			// If this is the first part of the body being received, try to reserve 
			// memory if content length is defined in the header.
			if (Request->BytesReceived == 0 && Request->WriteHeaderBufferPtr)
			{
				static const ANSICHAR* ContentLengthHeaderStr = "Content-Length: ";
				const ANSICHAR* Header = (const ANSICHAR*)Request->WriteHeaderBufferPtr->GetData();

				if (const ANSICHAR* ContentLengthHeader = FCStringAnsi::Strstr(Header, ContentLengthHeaderStr))
				{
					size_t ContentLength = (size_t)FCStringAnsi::Atoi64(ContentLengthHeader + strlen(ContentLengthHeaderStr));
					if (ContentLength > 0u && ContentLength < UE_HTTPDDC_MAX_BUFFER_RESERVE)
					{
						WriteDataBufferPtr->Reserve(ContentLength);
					}
				}
			}

			// Write to the target buffer
			WriteDataBufferPtr->Append((const uint8*)Ptr, WriteSize);
			Request->BytesReceived += WriteSize;
			return WriteSize;
		}
		
		return 0;
	}

	static size_t StaticSeekFn(void* UserData, curl_off_t Offset, int Origin)
	{
		FHttpRequest* Request = static_cast<FHttpRequest*>(UserData);
		size_t NewPosition = 0;

		switch (Origin)
		{
		case SEEK_SET: NewPosition = Offset; break;
		case SEEK_CUR: NewPosition = Request->BytesSent + Offset; break;
		case SEEK_END: NewPosition = Request->ReadDataView.Num() + Offset; break;
		}

		// Make sure we don't seek outside of the buffer
		if (NewPosition < 0 || NewPosition >= Request->ReadDataView.Num())
		{
			return CURL_SEEKFUNC_FAIL;
		}

		// Update the used offset
		Request->BytesSent = NewPosition;
		return CURL_SEEKFUNC_OK;
	}

};


//----------------------------------------------------------------------------------------------------------
// Forward declarations
//----------------------------------------------------------------------------------------------------------
bool VerifyPayload(const FSHAHash& Hash, const TCHAR* Namespace, const TCHAR* Bucket, const TCHAR* CacheKey, const TArray<uint8>& Payload);
bool VerifyPayload(const FIoHash& Hash, const TCHAR* Namespace, const TCHAR* Bucket, const TCHAR* CacheKey, const TArray<uint8>& Payload);
bool VerifyRequest(const class FHttpRequest* Request, const TCHAR* Namespace, const TCHAR* Bucket, const TCHAR* CacheKey, const TArray<uint8>& Payload);
bool HashPayload(class FHttpRequest* Request, const TArrayView<const uint8> Payload);
bool ShouldAbortForShutdown();

//----------------------------------------------------------------------------------------------------------
// Request pool
//----------------------------------------------------------------------------------------------------------


/**
 * Pool that manages a fixed set of requests. Users are required to release requests that have been 
 * acquired. Usable with \ref FScopedRequestPtr which handles this automatically.
 */
struct FRequestPool
{
	FRequestPool(const TCHAR* InServiceUrl, const TCHAR* InEffectiveServiceUrl, FHttpAccessToken* InAuthorizationToken, uint32 PoolSize)
	{
		Pool.AddUninitialized(PoolSize);
		for (uint8 i = 0; i < Pool.Num(); ++i)
		{
			Pool[i].Usage = 0u;
			Pool[i].Request = new FHttpRequest(InServiceUrl, InEffectiveServiceUrl, InAuthorizationToken, true);
		}
		
	}

	~FRequestPool()
	{
		for (uint8 i = 0; i < Pool.Num(); ++i)
		{
			// No requests should be in use by now.
			check(Pool[i].Usage.load(std::memory_order_acquire) == 0u);
			delete Pool[i].Request;
		}
	}

	/**
	 * Attempts to get a request is free. Once a request has been returned it is
	 * "owned by the caller and need to release it to the pool when work has been completed.
	 * @return Usable request instance if one is available, otherwise null.
	 */
	FHttpRequest* GetFreeRequest()
	{
		for (uint8 i = 0; i < Pool.Num(); ++i)
		{
			if (!Pool[i].Usage.load(std::memory_order_relaxed))
			{
				uint8 Expected = 0u;
				if (Pool[i].Usage.compare_exchange_strong(Expected, 1u))
				{
					Pool[i].Request->Reset();
					return Pool[i].Request;
				}
			}
		}
		return nullptr;
	}

	class FWaiter : public FThreadSafeRefCountedObject
	{
	public:
		std::atomic<FHttpRequest*> Request{ nullptr };

		FWaiter(FRequestPool* InPool)
			: Event(FPlatformProcess::GetSynchEventFromPool(true))
			, Pool(InPool)
		{
		}
		
		bool Wait(uint32 TimeMS)
		{
			return Event->Wait(TimeMS);
		}

		void Trigger()
		{
			Event->Trigger();
		}
	private:
		~FWaiter()
		{
			FPlatformProcess::ReturnSynchEventToPool(Event);

			if (Request)
			{
				Pool->ReleaseRequestToPool(Request.exchange(nullptr));
			}
		}

		FEvent* Event;
		FRequestPool* Pool;
	};

	/**
	 * Block until a request is free. Once a request has been returned it is 
	 * "owned by the caller and need to release it to the pool when work has been completed.
	 * @return Usable request instance.
	 */
	FHttpRequest* WaitForFreeRequest()
	{
		TRACE_CPUPROFILER_EVENT_SCOPE(HttpDDC_WaitForConnPool);

		FHttpRequest* Request = GetFreeRequest();
		if (Request == nullptr)
		{
			// Make it a fair by allowing each thread to register itself in a FIFO
			// so that the first thread to start waiting is the first one to get a request.
			FWaiter* Waiter = new FWaiter(this);
			Waiter->AddRef(); // One ref for the thread that will dequeue
			Waiter->AddRef(); // One ref for us

			Waiters.enqueue(Waiter);

			while (!Waiter->Wait(UE_HTTPDDC_BACKEND_WAIT_INTERVAL_MS))
			{
				// While waiting, allow us to check if a race occurred and a request has been freed
				// between the time we checked for free requests and the time we queued ourself as a Waiter.
				if ((Request = GetFreeRequest()) != nullptr)
				{
					// We abandon the FWaiter, it will be freed by the next dequeue
					// and if it has a request, it will be queued back to the pool.
					Waiter->Release();
					return Request;
				}
			}

			Request = Waiter->Request.exchange(nullptr);
			Request->Reset();
			Waiter->Release();
		}
		check(Request);
		return Request;
	}

	/**
	 * Release request to the pool.
	 * @param Request Request that should be freed. Note that any buffer owened by the request can now be reset.
	 */
	void ReleaseRequestToPool(FHttpRequest* Request)
	{
		for (uint8 i = 0; i < Pool.Num(); ++i)
		{
			if (Pool[i].Request == Request)
			{
				// If only 1 user is remaining, we can give it to a waiter
				// instead of releasing it back to the pool.
				if (Pool[i].Usage == 1u)
				{
					if (FWaiter* Waiter = Waiters.dequeue())
					{
						Waiter->Request = Request;
						Waiter->Trigger();
						Waiter->Release();
						return;
					}
				}
				
				Pool[i].Usage--;
				return;
			}
		}
		check(false);
	}

	/**
	 * While holding a request, make it shared across many users.
	 */
	void MakeRequestShared(FHttpRequest* Request, uint8 Users)
	{
		check(Users != 0);
		for (uint8 i = 0; i < Pool.Num(); ++i)
		{
			if (Pool[i].Request == Request)
			{
				Pool[i].Usage = Users;
				return;
			}
		}
		check(false);
	}

private:

	struct FEntry
	{
		std::atomic<uint8> Usage;
		FHttpRequest* Request;
	};

	TArray<FEntry> Pool;
	FAAArrayQueue<FWaiter> Waiters;

	FRequestPool() = delete;
};

//----------------------------------------------------------------------------------------------------------
// FScopedRequestPtr
//----------------------------------------------------------------------------------------------------------

/**
 * Utility class to manage requesting and releasing requests from the \ref FRequestPool.
 */
struct FScopedRequestPtr
{
public:
	FScopedRequestPtr(FRequestPool* InPool)
		: Request(InPool->WaitForFreeRequest())
		, Pool(InPool)
	{}

	~FScopedRequestPtr()
	{
		Pool->ReleaseRequestToPool(Request);
	}

	bool IsValid() const 
	{
		return Request != nullptr;
	}

	FHttpRequest* Get() const
	{
		check(IsValid());
		return Request;
	}

	FHttpRequest* operator->()
	{
		check(IsValid());
		return Request;
	}

private:
	FHttpRequest* Request;
	FRequestPool* Pool;
};


#if WITH_DATAREQUEST_HELPER

//----------------------------------------------------------------------------------------------------------
// FDataRequestHelper
//----------------------------------------------------------------------------------------------------------
/**
 * Helper class for requesting data. Will batch requests once the number of concurrent requests reach a threshold.
 */
struct FDataRequestHelper
{
	FDataRequestHelper(FRequestPool* InPool, const TCHAR* InNamespace, const TCHAR* InBucket, const TCHAR* InCacheKey, TArray<uint8>* OutData)
		: Request(nullptr)
		, Pool(InPool)
		, bVerified(false, 1)
	{
		Request = Pool->GetFreeRequest();
		if (Request && OutData != nullptr)
		{
			// We are below the threshold, make the connection immediately. OutData is set so this is a get.
			FString Uri = FString::Printf(TEXT("api/v1/c/ddc/%s/%s/%s.raw"), InNamespace, InBucket, InCacheKey);
			const FHttpRequest::Result Result = Request->PerformBlockingDownload(*Uri, OutData);
			if (FHttpRequest::IsSuccessResponse(Request->GetResponseCode()))
			{
				if (VerifyRequest(Request, InNamespace, InBucket, InCacheKey, *OutData))
				{
					TRACE_COUNTER_ADD(HttpDDC_GetHit, int64(1));
					TRACE_COUNTER_ADD(HttpDDC_BytesReceived, int64(Request->GetBytesReceived()));
					bVerified[0] = true;
				}
			}
		}
		else if (Request)
		{
			// We are below the threshold, make the connection immediately. OutData is missing so this is a head.
			FString Uri = FString::Printf(TEXT("api/v1/c/ddc/%s/%s/%s"), InNamespace, InBucket, InCacheKey);
			const FHttpRequest::Result Result = Request->PerformBlockingQuery<FHttpRequest::Head>(*Uri);
			if (FHttpRequest::IsSuccessResponse(Request->GetResponseCode()))
			{
				TRACE_COUNTER_ADD(HttpDDC_ExistHit, int64(1));
				bVerified[0] = true;
			}
		}
		else
		{
			// We have exceeded the threshold for concurrent connections, start or add this request
			// to a batched request.
			if (IsQueueCandidate(1, OutData && !OutData->IsEmpty()))
			{
				Request = QueueBatchRequest(
					InPool,
					InNamespace,
					InBucket,
					TConstArrayView<const TCHAR*>({InCacheKey}),
					OutData ? TConstArrayView<TArray<uint8>*>({OutData}) : TConstArrayView<TArray<uint8>*>(),
					bVerified
				);
			}

			if (!Request)
			{
				Request = Pool->WaitForFreeRequest();

				FQueuedBatchEntry Entry{
					InNamespace,
					InBucket,
					TConstArrayView<const TCHAR*>({InCacheKey}),
					OutData ? TConstArrayView<TArray<uint8>*>({OutData}) : TConstArrayView<TArray<uint8>*>(),
					OutData && !OutData->IsEmpty() ? FHttpRequest::RequestVerb::Get : FHttpRequest::RequestVerb::Head,
					&bVerified
				};

				PerformBatchQuery(Request, TArrayView<FQueuedBatchEntry>(&Entry, 1));
			}
		}
	}

	// Constructor specifically for batched head queries
	FDataRequestHelper(FRequestPool* InPool, const TCHAR* InNamespace, const TCHAR* InBucket, TConstArrayView<FString> InCacheKeys)
		: Request(nullptr)
		, Pool(InPool)
		, bVerified(false, InCacheKeys.Num())
	{
		// Transform the FString array to char pointers
		TArray<const TCHAR*> CacheKeys;
		Algo::Transform(InCacheKeys, CacheKeys, [](const FString& Key) { return *Key; });
		
		Request = Pool->GetFreeRequest();

		if (Request || !IsQueueCandidate(InCacheKeys.Num(), false))
		{
			// If the request is too big for existing batches, wait for a free connection and create our own.
			if (!Request)
			{
				Request = Pool->WaitForFreeRequest();
			}

			FQueuedBatchEntry Entry{
				InNamespace, 
				InBucket,
				CacheKeys,
				TConstArrayView<TArray<uint8>*>(),
				FHttpRequest::RequestVerb::Head,
				&bVerified
			};

			PerformBatchQuery(Request, TArrayView<FQueuedBatchEntry>(&Entry, 1));
		}
		else
		{
			Request = QueueBatchRequest(
				InPool, 
				InNamespace, 
				InBucket, 
				CacheKeys, 
				TConstArrayView<TArray<uint8>*>(), 
				bVerified
			);

			if (!Request)
			{
				Request = Pool->WaitForFreeRequest();

				FQueuedBatchEntry Entry{
					InNamespace,
					InBucket,
					CacheKeys,
					TConstArrayView<TArray<uint8>*>(),
					FHttpRequest::RequestVerb::Head,
					&bVerified
				};

				PerformBatchQuery(Request, TArrayView<FQueuedBatchEntry>(&Entry, 1));
			}
		}
	}

	~FDataRequestHelper()
	{
		if (Request)
		{
			Pool->ReleaseRequestToPool(Request);
		}
	}

	static void StaticInitialize()
	{
		static bool bInitialized = false;
		check(!bInitialized);
		for (FBatch& Batch : Batches)
		{
			Batch.Reserved = 0;
			Batch.Ready = 0;
			Batch.Complete = TUniquePtr<FEvent, FBatch::FEventDeleter>(FPlatformProcess::GetSynchEventFromPool(true));
		}
		bInitialized = true;
	}

	static void StaticShutdown()
	{
		for (FBatch& Batch : Batches)
		{
			Batch.Complete.Reset();
		}
	}

	bool IsSuccess() const
	{
		return bVerified[0];
	}

	const TBitArray<>& IsBatchSuccess() const
	{
		return bVerified;
	}

	int64 GetResponseCode() const
	{
		return Request ? Request->GetResponseCode() : 0;
	}

private:

	struct FQueuedBatchEntry
	{
		const TCHAR* Namespace;
		const TCHAR* Bucket;
		TConstArrayView<const TCHAR*> CacheKeys;
		TConstArrayView<TArray<uint8>*> OutDatas;
		FHttpRequest::RequestVerb Verb;
		TBitArray<>* bSuccess;
	};

	struct FBatch
	{
		struct FEventDeleter
		{
			void operator()(FEvent* Event)
			{
				FPlatformProcess::ReturnSynchEventToPool(Event);
			}
		};

		FQueuedBatchEntry Entries[UE_HTTPDDC_BATCH_SIZE];
		std::atomic<uint32> Reserved;
		std::atomic<uint32> Ready;
		std::atomic<uint32> WeightHint;
		FHttpRequest* Request;
		TUniquePtr<FEvent, FEventDeleter> Complete;
	};

	FHttpRequest* Request;
	FRequestPool* Pool;
	TBitArray<> bVerified;
	static std::atomic<uint32> FirstAvailableBatch;
	static TStaticArray<FBatch, UE_HTTPDDC_BATCH_NUM> Batches;

	static uint32 ComputeWeight(int32 NumKeys, bool bHasDatas)
	{
		return NumKeys * (bHasDatas ? UE_HTTPDDC_BATCH_GET_WEIGHT : UE_HTTPDDC_BATCH_HEAD_WEIGHT);
	}

	static bool IsQueueCandidate(int32 NumKeys, bool bHasDatas)
	{
		if (NumKeys > UE_HTTPDDC_BATCH_SIZE)
		{
			return false;
		}
		const uint32 Weight = ComputeWeight(NumKeys, bHasDatas);
		if (Weight > UE_HTTPDDC_BATCH_WEIGHT_HINT)
		{
			return false;
		}
		return true;
	}

	/**
	 * Queues up a request to be batched. Blocks until the query is made.
	 */
	static FHttpRequest* QueueBatchRequest(FRequestPool* InPool, 
		const TCHAR* InNamespace, 
		const TCHAR* InBucket, 
		TConstArrayView<const TCHAR*> InCacheKeys,
		TConstArrayView<TArray<uint8>*> OutDatas, 
		TBitArray<>& bOutVerified)
	{
		TRACE_CPUPROFILER_EVENT_SCOPE(HttpDDC_BatchQuery);
		check(InCacheKeys.Num() == OutDatas.Num() || OutDatas.Num() == 0);
		const uint32 RequestNum = InCacheKeys.Num();
		const uint32 RequestWeight = ComputeWeight(InCacheKeys.Num(), !OutDatas.IsEmpty());

		for (int32 i = 0; i < Batches.Num(); i++)
		{
			uint32 Index = (FirstAvailableBatch.load(std::memory_order_relaxed) + i) % Batches.Num();
			FBatch& Batch = Batches[Index];

			//Assign different weights to head vs. get queries
			if (Batch.WeightHint.load(std::memory_order_acquire) + RequestWeight > UE_HTTPDDC_BATCH_WEIGHT_HINT)
			{
				continue;
			}

			// Attempt to reserve a spot in the batch
			const uint32 Reserve = Batch.Reserved.fetch_add(1, std::memory_order_acquire);
			if (Reserve >= UE_HTTPDDC_BATCH_SIZE)
			{
				// We didn't manage to snag a valid reserve index try next batch
				continue;
			}

			// Add our weight to the batch. Note we are treating it as a hint, so don't syncronize.
			const uint32 ActualWeight = Batch.WeightHint.fetch_add(RequestWeight, std::memory_order_release);

			TAnsiStringBuilder<64> BatchString;
			BatchString << "HttpDDC_Batch" << Index;
			TRACE_CPUPROFILER_EVENT_SCOPE_TEXT(*BatchString);

			if (Reserve == (UE_HTTPDDC_BATCH_SIZE - 1))
			{
				FirstAvailableBatch++;
			}

			Batch.Entries[Reserve] = FQueuedBatchEntry{
				InNamespace,
				InBucket,
				InCacheKeys,
				OutDatas,
				OutDatas.Num() ? FHttpRequest::RequestVerb::Get : FHttpRequest::RequestVerb::Head,
				&bOutVerified
			};

			// Signal we are ready for batch to be submitted
			Batch.Ready.fetch_add(1u, std::memory_order_release);

			FHttpRequest* Request = nullptr;

			// The first to reserve a slot is the "driver" of the batch
			if (Reserve == 0)
			{
				Batch.Request = InPool->WaitForFreeRequest();

				// Make sure no new requests are added
				const uint32 Reserved = FMath::Min((uint32)UE_HTTPDDC_BATCH_SIZE, Batch.Reserved.fetch_add(UE_HTTPDDC_BATCH_SIZE, std::memory_order_acquire));

				// Give other threads time to copy their data to batch
				while (Batch.Ready.load(std::memory_order_acquire) < Reserved) {}

				// Increment request ref count to reflect all waiting threads
				InPool->MakeRequestShared(Batch.Request, Reserved);

				// Do the actual query and write response to respective target arrays
				PerformBatchQuery(Batch.Request, TArrayView<FQueuedBatchEntry>(Batch.Entries, Batch.Ready));

				// Signal to waiting threads the batch is complete
				Batch.Complete->Trigger();

				// Store away the request and wait until other threads have too
				Request = Batch.Request;
				while (Batch.Ready.load(std::memory_order_acquire) > 1) {}

				//Reset batch for next use
				Batch.Complete->Reset();
				Batch.WeightHint.store(0, std::memory_order_release);
				Batch.Ready.store(0, std::memory_order_release);
				Batch.Reserved.store(0, std::memory_order_release);
			}
			else
			{
				// Wait until "driver" has done query
				{
					TRACE_CPUPROFILER_EVENT_SCOPE(WaitForMasterOfBatch);
					Batch.Complete->Wait(~0);
				}

				// Store away request and signal we are done
				Request = Batch.Request;
				Batch.Ready.fetch_sub(1u, std::memory_order_release);
			}

			return Request;
		}

		return nullptr;
	}


	/**
	 * Creates request uri and headers and submits the request
	 */
	static void PerformBatchQuery(FHttpRequest* Request, TArrayView<FQueuedBatchEntry> Entries)
	{
		TRACE_CPUPROFILER_EVENT_SCOPE(HttpDDC_BatchGet);
		const TCHAR* Uri(TEXT("api/v1/c/ddc-rpc/batchget"));
		int64 ResponseCode = 0; uint32 Attempts = 0;

		//Prepare request object
		TArray<TSharedPtr<FJsonValue>> Operations;
		for (const FQueuedBatchEntry& Entry : Entries)
		{
			for (int32 KeyIdx = 0; KeyIdx < Entry.CacheKeys.Num(); KeyIdx++)
			{
				TSharedPtr<FJsonObject> Object = MakeShared<FJsonObject>();
				Object->SetField(TEXT("bucket"), MakeShared<FJsonValueString>(Entry.Bucket));
				Object->SetField(TEXT("key"), MakeShared<FJsonValueString>(Entry.CacheKeys[KeyIdx]));
				if (Entry.Verb == FHttpRequest::RequestVerb::Head)
				{
					Object->SetField(TEXT("verb"), MakeShared<FJsonValueString>(TEXT("HEAD")));
				}
				Operations.Add(MakeShared<FJsonValueObject>(Object));
			}
		}
		TSharedPtr<FJsonObject> RequestObject = MakeShared<FJsonObject>();
		RequestObject->SetField(TEXT("namespace"), MakeShared<FJsonValueString>(Entries[0].Namespace));
		RequestObject->SetField(TEXT("operations"), MakeShared<FJsonValueArray>(Operations));

		//Serialize to a buffer
		FBufferArchive RequestData;
		if (FJsonSerializer::Serialize(RequestObject.ToSharedRef(), TJsonWriterFactory<ANSICHAR, TCondensedJsonPrintPolicy<ANSICHAR>>::Create(&RequestData)))
		{
			Request->PerformBlockingUpload<FHttpRequest::PostJson>(Uri, MakeArrayView(RequestData));
			ResponseCode = Request->GetResponseCode();

			if (ResponseCode == 200)
			{
				const TArray<uint8>& ResponseBuffer = Request->GetResponseBuffer();
				const uint8* Response = ResponseBuffer.GetData();
				const int32 ResponseSize = ResponseBuffer.Num();

				// Parse the response and move the data to the target requests.
				if (ParseBatchedResponse(Response, ResponseSize, Entries))
				{
					UE_LOG(LogDerivedDataCache, VeryVerbose, TEXT("%s: Batch query with %d operations completed."), *Request->GetName(), Entries.Num());
					return;
				}
			}
		}
		
		// If we get here the request failed.
		UE_LOG(LogDerivedDataCache, Display, TEXT("%s: Batch query failed. Query: %s"), *Request->GetName(), ANSI_TO_TCHAR((ANSICHAR*)RequestData.GetData()));

		// Set all batch operations to failures
		for (FQueuedBatchEntry Entry : Entries)
		{
			Entry.bSuccess->SetRange(0, Entry.CacheKeys.Num(), false);
		}
	}

	// Above result value
	enum class OpResult : uint8
	{
		Ok = 0,			// Op finished succesfully
		Error = 1,		// Error during op
		NotFound = 2,	// Key was not found
		Exists = 3		// Used to indicate head op success
	};

	// Searches for potentially multiple key requests that are satisfied the given cache key result
	// Search strategy is exhaustive forward search from the last found entry.  If the results come in ordered the same as the requests,
	//  and there are no duplicates, the search will be somewhat efficient (still has to do exhaustive searching looking for duplicates).
	//  If the results are unordered or there are duplicates, search will become more inefficient.
	struct FRequestSearchHelper
	{
		FRequestSearchHelper(TArrayView<FQueuedBatchEntry> InRequests, const FUTF8ToTCHAR& InCacheKey, int32 InEntryIdx, int32 InKeyIdx, OpResult InRequestResult)
			: Requests(InRequests)
			, CacheKey(InCacheKey)
			, StartEntryIdx(InEntryIdx)
			, StartKeyIdx(InKeyIdx)
			, RequestResult(InRequestResult)
		{}

		bool FindNext(int32& EntryIdx, int32& KeyIdx)
		{
			int32 CurrentEntryIdx = EntryIdx;
			int32 CurrentKeyIdx = KeyIdx;
			do
			{
				// Do not match a get request with a head response code (i.e. Exists) 
				// or a head request with a get response code (i.e. Ok)
				// if the response code is an error or not found they can be matched to both head or get request it doesn't matter
				const FQueuedBatchEntry& CurrentRequest = Requests[CurrentEntryIdx];
				bool bRequestTypeMatch = !((CurrentRequest.Verb == FHttpRequest::Get) && (RequestResult == OpResult::Exists))
					&& !((CurrentRequest.Verb == FHttpRequest::Head) && (RequestResult == OpResult::Ok));
				if (bRequestTypeMatch && FCString::Stricmp(CurrentRequest.CacheKeys[CurrentKeyIdx], CacheKey.Get()) == 0)
				{
					EntryIdx = CurrentEntryIdx;
					KeyIdx = CurrentKeyIdx;
					return true;
				}
			} while (AdvanceIndices(CurrentEntryIdx, CurrentKeyIdx));

			return false;
		}

		bool AdvanceIndices(int32& EntryIdx, int32& KeyIdx)
		{
			if (++KeyIdx >= Requests[EntryIdx].CacheKeys.Num())
			{
				EntryIdx = (EntryIdx + 1) % Requests.Num();
				KeyIdx = 0;
			}

			return !((EntryIdx == StartEntryIdx) && (KeyIdx == StartKeyIdx));
		}

		TArrayView<FQueuedBatchEntry> Requests;
		const FUTF8ToTCHAR& CacheKey;
		int32 StartEntryIdx;
		int32 StartKeyIdx;
		OpResult RequestResult;
	};

	/**
	 * Parses a batched response stream, moves the data to target requests and marks them with result.
	 * @param Response Pointer to Response buffer
	 * @param ResponseSize Size of response buffer
	 * @param Requests Requests that will be filled with data.
	 * @return True if response was successfully parsed, false otherwise.
	 */
	static bool ParseBatchedResponse(const uint8* ResponseStart, const int32 ResponseSize, TArrayView<FQueuedBatchEntry> Requests)
	{
		// The expected data stream is structured accordingly
		// {"JPTR"} {PayloadCount:uint32} {{"JPEE"} {Name:cstr} {Result:uint8} {Hash:IoHash} {Size:uint64} {Payload...}} ...

		const auto& ResponseErrorMessage = TEXT("Malformed response from server.");
		const ANSICHAR* ProtocolMagic = "JPTR";
		const ANSICHAR* PayloadMagic = "JPEE";
		const uint32 MagicSize = 4;
		const uint8* Response = ResponseStart;
		const uint8* ResponseEnd = Response + ResponseSize;

		// Check that the stream starts with the protocol magic
		if (FMemory::Memcmp(ProtocolMagic, Response, MagicSize) != 0)
		{
			UE_LOG(LogDerivedDataCache, Display, ResponseErrorMessage);
			return false;
		}
		Response += MagicSize;

		// Number of payloads recieved
		uint32 PayloadCount = *(uint32*)Response;
		Response += sizeof(uint32);

		uint32 PayloadIdx = 0; 	// Current processed result
		int32 EntryIdx = 0; 	// Current Entry index
		int32 KeyIdx = 0; 		// Current Key index for current Entry

		while (Response < ResponseEnd && FMemory::Memcmp(PayloadMagic, Response, MagicSize) == 0)
		{
			PayloadIdx++;
			Response += MagicSize;

			const ANSICHAR* PayloadNameA = (const ANSICHAR*)Response;
			Response += FCStringAnsi::Strlen(PayloadNameA) + 1; //String and zero termination
			const ANSICHAR* CacheKeyA = FCStringAnsi::Strrchr(PayloadNameA, '.') + 1; // "namespace.bucket.cachekey"

			// Result of the operation is used to match to the appropriate request (i.e. get or head)
			OpResult PayloadResult = static_cast<OpResult>(*Response);
			Response += sizeof(uint8);

			const uint8* ResponseRewindMark = Response;

			// Find the payload among the requests.  Payloads may be returned in any order and if the same cache key was part of two requests,
			// a single payload may satisfy multiple cache keys in multiple requests.
			FUTF8ToTCHAR CacheKey(CacheKeyA);
			FRequestSearchHelper RequestSearch(Requests, CacheKey, EntryIdx, KeyIdx, PayloadResult);
			bool bFoundAny = false;

			while (RequestSearch.FindNext(EntryIdx, KeyIdx))
			{
				Response = ResponseRewindMark;
				bFoundAny = true;

				FQueuedBatchEntry& RequestOp = Requests[EntryIdx];
				TBitArray<>& bSuccess = *RequestOp.bSuccess;

				switch (PayloadResult)
				{
				case OpResult::Ok:
					{
						// Payload hash of the following payload data
						FIoHash PayloadHash = *(FIoHash*)Response;
						Response += sizeof(FIoHash);

						// Size of the following payload data
						const uint64 PayloadSize = *(uint64*)Response;
						Response += sizeof(uint64);

						if (PayloadSize > 0)
						{
							if (Response + PayloadSize > ResponseEnd)
							{
								UE_LOG(LogDerivedDataCache, Display, ResponseErrorMessage);
								return false;
							}

							if (bSuccess[KeyIdx])
							{
								Response += PayloadSize;
							}
							else
							{
								TArray<uint8>* OutData = RequestOp.OutDatas[KeyIdx];

								OutData->Append(Response, PayloadSize);
								Response += PayloadSize;
								// Verify the received and parsed payload
								if (VerifyPayload(PayloadHash, RequestOp.Namespace, RequestOp.Bucket, RequestOp.CacheKeys[KeyIdx], *OutData))
								{
									TRACE_COUNTER_ADD(HttpDDC_GetHit, int64(1));
									TRACE_COUNTER_ADD(HttpDDC_BytesReceived, int64(PayloadSize));
									
									bSuccess[KeyIdx] = true;
								}
								else
								{
									OutData->Empty();
									bSuccess[KeyIdx] = false;
								}
							}
						}
						else
						{
							bSuccess[KeyIdx] = false;
						}
					}
					break;

				case OpResult::Exists:
					{
						TRACE_COUNTER_ADD(HttpDDC_ExistHit, int64(1));
						bSuccess[KeyIdx] = true;
					}
					break;

				default:
				case OpResult::Error:
					UE_LOG(LogDerivedDataCache, Display, TEXT("Server error while getting %s"), CacheKey.Get());
					// intentional falltrough

				case OpResult::NotFound:
					bSuccess[KeyIdx] = false;
					break;

				}

				if (!RequestSearch.AdvanceIndices(EntryIdx, KeyIdx))
				{
					break;
				}
			}

			if (!bFoundAny)
			{
				UE_LOG(LogDerivedDataCache, Error, ResponseErrorMessage);
				return false;
			}
		}

		// Have we parsed all the payloads from the message?
		if (PayloadIdx != PayloadCount)
		{
			UE_LOG(LogDerivedDataCache, Display, TEXT("%s: Found %d payloads but %d was reported."), ResponseErrorMessage, PayloadIdx, PayloadCount);
		}

		return true;
	}
};

TStaticArray<FDataRequestHelper::FBatch, UE_HTTPDDC_BATCH_NUM> FDataRequestHelper::Batches;
std::atomic<uint32> FDataRequestHelper::FirstAvailableBatch;

//----------------------------------------------------------------------------------------------------------
// FDataUploadHelper
//----------------------------------------------------------------------------------------------------------
struct FDataUploadHelper
{
	FDataUploadHelper(FRequestPool* InPool, 
		const TCHAR* InNamespace, 
		const TCHAR* InBucket, 
		const TCHAR* InCacheKey, 
		const TArrayView<const uint8>& InData,
		FDerivedDataCacheUsageStats& InUsageStats)
		: ResponseCode(0)
		, bSuccess(false)
		, bQueued(false)
	{
		FHttpRequest* Request = InPool->GetFreeRequest();
		if (Request)
		{
			ResponseCode = PerformPut(Request, InNamespace, InBucket, InCacheKey, InData, InUsageStats);
			bSuccess = FHttpRequest::IsSuccessResponse(Request->GetResponseCode());

			ProcessQueuedPutsAndReleaseRequest(InPool, Request, InUsageStats);
		}
		else
		{
			FQueuedEntry* Entry = new FQueuedEntry(InNamespace, InBucket, InCacheKey, InData);
			QueuedPuts.Push(Entry);
			bSuccess = true;
			bQueued = true;
			
			// A request may have been released while the entry was being queued.
			Request = InPool->GetFreeRequest();
			if (Request)
			{
				ProcessQueuedPutsAndReleaseRequest(InPool, Request, InUsageStats);
			}
		}
	}

	bool IsSuccess() const
	{
		return bSuccess;
	}

	int64 GetResponseCode() const
	{
		return ResponseCode;
	}

	bool IsQueued() const
	{
		return bQueued;
	}

private:

	struct FQueuedEntry
	{
		FString Namespace;
		FString Bucket;
		FString CacheKey;
		TArray<uint8> Data;

		FQueuedEntry(const TCHAR* InNamespace, const TCHAR* InBucket, const TCHAR* InCacheKey, const TArrayView<const uint8> InData)
			: Namespace(InNamespace)
			, Bucket(InBucket)
			, CacheKey(InCacheKey)
			, Data(InData) // Copies the data!
		{}
	};

	static TLockFreePointerListUnordered<FQueuedEntry, PLATFORM_CACHE_LINE_SIZE> QueuedPuts;

	int64 ResponseCode;
	bool bSuccess;
	bool bQueued;

	static void ProcessQueuedPutsAndReleaseRequest(FRequestPool* Pool, FHttpRequest* Request, FDerivedDataCacheUsageStats& UsageStats)
	{
		while (Request)
		{
			// Make sure that whether we early exit or execute past the end of this scope that
			// the request is released back to the pool.
			{
				ON_SCOPE_EXIT
				{
					Pool->ReleaseRequestToPool(Request);
				};

				if (ShouldAbortForShutdown())
				{
					return;
				}

				while (FQueuedEntry* Entry = QueuedPuts.Pop())
				{
					Request->Reset();
					PerformPut(Request, *Entry->Namespace, *Entry->Bucket, *Entry->CacheKey, Entry->Data, UsageStats);
					delete Entry;

					if (ShouldAbortForShutdown())
					{
						return;
					}
				}
			}

			// An entry may have been queued while the request was being released.
			if (QueuedPuts.IsEmpty())
			{
				break;
			}

			// Process the queue again if a request is free, otherwise the thread that got the request will process it.
			Request = Pool->GetFreeRequest();
		}
	}

	static int64 PerformPut(FHttpRequest* Request, const TCHAR* Namespace, const TCHAR* Bucket, const TCHAR* CacheKey, const TArrayView<const uint8> Data, FDerivedDataCacheUsageStats& UsageStats)
	{
		COOK_STAT(auto Timer = UsageStats.TimePut());

		HashPayload(Request, Data);

		TStringBuilder<256> Uri;
		Uri.Appendf(TEXT("api/v1/c/ddc/%s/%s/%s"), Namespace, Bucket, CacheKey);

		Request->PerformBlockingUpload<FHttpRequest::Put>(*Uri, Data);

		const int64 ResponseCode = Request->GetResponseCode();
		if (FHttpRequest::IsSuccessResponse(ResponseCode))
		{
			TRACE_COUNTER_ADD(HttpDDC_BytesSent, int64(Request->GetBytesSent()));
			COOK_STAT(Timer.AddHit(Request->GetBytesSent()));
		}

		return Request->GetResponseCode();
	}
};

TLockFreePointerListUnordered<FDataUploadHelper::FQueuedEntry, PLATFORM_CACHE_LINE_SIZE> FDataUploadHelper::QueuedPuts;

#endif // WITH_DATAREQUEST_HELPER

//----------------------------------------------------------------------------------------------------------
// Certificate checking
//----------------------------------------------------------------------------------------------------------

#if WITH_SSL

static int SslCertVerify(int PreverifyOk, X509_STORE_CTX* Context)
{
	if (PreverifyOk == 1)
	{
		SSL* Handle = static_cast<SSL*>(X509_STORE_CTX_get_ex_data(Context, SSL_get_ex_data_X509_STORE_CTX_idx()));
		check(Handle);

		SSL_CTX* SslContext = SSL_get_SSL_CTX(Handle);
		check(SslContext);

		FHttpRequest* Request = static_cast<FHttpRequest*>(SSL_CTX_get_app_data(SslContext));
		check(Request);

		const FString& Domain = Request->GetDomain();

		if (!FSslModule::Get().GetCertificateManager().VerifySslCertificates(Context, Domain))
		{
			PreverifyOk = 0;
		}
	}

	return PreverifyOk;
}

static CURLcode sslctx_function(CURL * curl, void * sslctx, void * parm)
{
	SSL_CTX* Context = static_cast<SSL_CTX*>(sslctx);
	const ISslCertificateManager& CertificateManager = FSslModule::Get().GetCertificateManager();

	CertificateManager.AddCertificatesToSslContext(Context);
	SSL_CTX_set_verify(Context, SSL_CTX_get_verify_mode(Context), SslCertVerify);
	SSL_CTX_set_app_data(Context, parm);

	/* all set to go */
	return CURLE_OK;
}

#endif //#if WITH_SSL

//----------------------------------------------------------------------------------------------------------
// Content parsing and checking
//----------------------------------------------------------------------------------------------------------

/**
 * Verifies the integrity of the received data using supplied checksum.
 * @param Hash received hash value.
 * @param Namespace The namespace string used when originally fetching the request.
 * @param Bucket The bucket string used when originally fetching the request.
 * @param CacheKey The cache key string used when originally fetching the request.
 * @param Payload Payload received.
 * @return True if the data is correct, false if checksums doesn't match.
 */
bool VerifyPayload(const FSHAHash& Hash, const TCHAR* Namespace, const TCHAR* Bucket, const TCHAR* CacheKey, const TArray<uint8>& Payload)
{
	FSHAHash PayloadHash;
	FSHA1::HashBuffer(Payload.GetData(), Payload.Num(), PayloadHash.Hash);

	if (Hash != PayloadHash)
	{
		UE_LOG(LogDerivedDataCache,
			Display,
			TEXT("Checksum from server did not match received data (%s vs %s). Discarding cached result. Namespace: %s, Bucket: %s, Key: %s."),
			*WriteToString<48>(Hash),
			*WriteToString<48>(PayloadHash),
			Namespace,
			Bucket,
			CacheKey
		);
		return false;
	}

	return true;
}

/**
 * Verifies the integrity of the received data using supplied checksum.
 * @param Hash received hash value.
 * @param Namespace The namespace string used when originally fetching the request.
 * @param Bucket The bucket string used when originally fetching the request.
 * @param CacheKey The cache key string used when originally fetching the request.
 * @param Payload Payload received.
 * @return True if the data is correct, false if checksums doesn't match.
 */
bool VerifyPayload(const FIoHash& Hash, const TCHAR* Namespace, const TCHAR* Bucket, const TCHAR* CacheKey, const TArray<uint8>& Payload)
{
	FIoHash PayloadHash = FIoHash::HashBuffer(Payload.GetData(), Payload.Num());

	if (Hash != PayloadHash)
	{
		UE_LOG(LogDerivedDataCache,
			Display,
			TEXT("Checksum from server did not match received data (%s vs %s). Discarding cached result. Namespace: %s, Bucket: %s, Key: %s."),
			*WriteToString<48>(Hash),
			*WriteToString<48>(PayloadHash),
			Namespace,
			Bucket,
			CacheKey
		);
		return false;
	}

	return true;
}


/**
 * Verifies the integrity of the received data using supplied checksum.
 * @param Request Request that the data was be received with.
 * @param Namespace The namespace string used when originally fetching the request.
 * @param Bucket The bucket string used when originally fetching the request.
 * @param CacheKey The cache key string used when originally fetching the request.
 * @param Payload Payload received.
 * @return True if the data is correct, false if checksums doesn't match.
 */
bool VerifyRequest(const FHttpRequest* Request, const TCHAR* Namespace, const TCHAR* Bucket, const TCHAR* CacheKey, const TArray<uint8>& Payload)
{
	FString ReceivedHashStr;
	if (Request->GetHeader("X-Jupiter-Sha1", ReceivedHashStr))
	{
		FSHAHash ReceivedHash;
		ReceivedHash.FromString(ReceivedHashStr);
		return VerifyPayload(ReceivedHash, Namespace, Bucket, CacheKey, Payload);
	}
	if (Request->GetHeader("X-Jupiter-IoHash", ReceivedHashStr))
	{
		FIoHash ReceivedHash(ReceivedHashStr);
		return VerifyPayload(ReceivedHash, Namespace, Bucket, CacheKey, Payload);
	}
	UE_LOG(LogDerivedDataCache, Warning, TEXT("%s: HTTP server did not send a content hash. Wrong server version?"), *Request->GetName());
	return true;
}

/**
 * Adds a checksum (as request header) for a given payload. Jupiter will use this to verify the integrity
 * of the received data.
 * @param Request Request that the data will be sent with.
 * @param Payload Payload that will be sent.
 * @return True on success, false on failure.
 */
bool HashPayload(FHttpRequest* Request, const TArrayView<const uint8> Payload)
{
	FIoHash PayloadHash = FIoHash::HashBuffer(Payload.GetData(), Payload.Num());
	Request->SetHeader(TEXT("X-Jupiter-IoHash"), *WriteToString<48>(PayloadHash));
	return true;
}

bool ShouldAbortForShutdown()
{
	return !GIsBuildMachine && FDerivedDataBackend::Get().IsShuttingDown();
}

TConstArrayView<uint8> MakeConstArrayView(FSharedBuffer Buffer)
{
	return TConstArrayView<uint8>(reinterpret_cast<const uint8*>(Buffer.GetData()), Buffer.GetSize());
}

static bool IsValueDataReady(FValue& Value, const ECachePolicy Policy)
{
	if (!EnumHasAnyFlags(Policy, ECachePolicy::Query))
	{
		Value = Value.RemoveData();
		return true;
	}

	if (Value.HasData())
	{
		if (EnumHasAnyFlags(Policy, ECachePolicy::SkipData))
		{
			Value = Value.RemoveData();
		}
		return true;
	}
	return false;
};

//----------------------------------------------------------------------------------------------------------
// FHttpAccessToken
//----------------------------------------------------------------------------------------------------------

FString FHttpAccessToken::GetHeader()
{
	Lock.ReadLock();
	FString Header = FString::Printf(TEXT("Authorization: Bearer %s"), *Token);
	Lock.ReadUnlock();
	return Header;
}

void FHttpAccessToken::SetHeader(const TCHAR* InToken)
{
	Lock.WriteLock();
	Token = InToken;
	Serial++;
	Lock.WriteUnlock();
}

uint32 FHttpAccessToken::GetSerial() const
{
	return Serial;
}

//----------------------------------------------------------------------------------------------------------
// FHttpCacheStore
//----------------------------------------------------------------------------------------------------------

/**
 * Backend for a HTTP based caching service (Jupiter).
 **/
class FHttpCacheStore final : public FDerivedDataBackendInterface
{
public:
	
	/**
	 * Creates the backend, checks health status and attempts to acquire an access token.
	 *
	 * @param ServiceUrl			Base url to the service including schema.
	 * @param Namespace				Namespace to use.
	 * @param StructuredNamespace	Namespace to use for structured cache operations.
	 * @param OAuthProvider			Url to OAuth provider, for example "https://myprovider.com/oauth2/v1/token".
	 * @param OAuthClientId			OAuth client identifier.
	 * @param OAuthData				OAuth form data to send to login service. Can either be the raw form data or a Windows network file address (starting with "\\").
	 * @param OAuthScope			OAuth scope identifier
	 */
	FHttpCacheStore(
		const TCHAR* ServiceUrl, 
		bool bResolveHostCanonicalName,
		const TCHAR* Namespace, 
		const TCHAR* StructuredNamespace, 
		const TCHAR* OAuthProvider, 
		const TCHAR* OAuthClientId, 
		const TCHAR* OAuthData,
		const TCHAR* OAuthScope,
		EBackendLegacyMode LegacyMode,
		bool bReadOnly);

	~FHttpCacheStore();

	/**
	 * Checks is backend is usable (reachable and accessible).
	 * @return true if usable
	 */
	bool IsUsable() const { return bIsUsable; }

	/** return true if this cache is writable **/
	virtual bool IsWritable() const override
	{
		return !bReadOnly && bIsUsable;
	}

	virtual bool CachedDataProbablyExists(const TCHAR* CacheKey) override;
	virtual TBitArray<> CachedDataProbablyExistsBatch(TConstArrayView<FString> CacheKeys) override;
	virtual bool GetCachedData(const TCHAR* CacheKey, TArray<uint8>& OutData) override;
	virtual EPutStatus PutCachedData(const TCHAR* CacheKey, TArrayView<const uint8> InData, bool bPutEvenIfExists) override;
	virtual void RemoveCachedData(const TCHAR* CacheKey, bool bTransient) override;
	virtual TSharedRef<FDerivedDataCacheStatsNode> GatherUsageStats() const override;
	
	virtual FString GetName() const override;
	virtual TBitArray<> TryToPrefetch(TConstArrayView<FString> CacheKeys) override;
	virtual bool WouldCache(const TCHAR* CacheKey, TArrayView<const uint8> InData) override;
	virtual ESpeedClass GetSpeedClass() const override;
	virtual bool ApplyDebugOptions(FBackendDebugOptions& InOptions) override;

	void SetSpeedClass(ESpeedClass InSpeedClass) { SpeedClass = InSpeedClass; }

	EBackendLegacyMode GetLegacyMode() const final { return LegacyMode; }

	virtual void Put(
		TConstArrayView<FCachePutRequest> Requests,
		IRequestOwner& Owner,
		FOnCachePutComplete&& OnComplete) override;

	virtual void Get(
		TConstArrayView<FCacheGetRequest> Requests,
		IRequestOwner& Owner,
		FOnCacheGetComplete&& OnComplete) override;
	virtual void PutValue(
		TConstArrayView<FCachePutValueRequest> Requests,
		IRequestOwner& Owner,
		FOnCachePutValueComplete&& OnComplete) override;
	virtual void GetValue(
		TConstArrayView<FCacheGetValueRequest> Requests,
		IRequestOwner& Owner,
		FOnCacheGetValueComplete&& OnComplete) override;
	virtual void GetChunks(
		TConstArrayView<FCacheGetChunkRequest> Requests,
		IRequestOwner& Owner,
		FOnCacheGetChunkComplete&& OnComplete) override;

	static FHttpCacheStore* GetAny()
	{
		return AnyInstance;
	}

	const FString& GetDomain() const { return Domain; }
	const FString& GetNamespace() const { return Namespace; }
	const FString& GetStructuredNamespace() const { return StructuredNamespace; }
	const FString& GetOAuthProvider() const { return OAuthProvider; }
	const FString& GetOAuthClientId() const { return OAuthClientId; }
	const FString& GetOAuthSecret() const { return OAuthSecret; }
	const FString& GetOAuthScope() const { return OAuthScope; }

private:
	FString Domain;
	FString Namespace;
	FString StructuredNamespace;
	FString DefaultBucket;
	FString OAuthProvider;
	FString OAuthClientId;
	FString OAuthSecret;
	FString OAuthScope;
	FCriticalSection AccessCs;
	FDerivedDataCacheUsageStats UsageStats;
	FBackendDebugOptions DebugOptions;
	FCriticalSection MissedKeysCS;
	TSet<FName> DebugMissedKeys;
	TSet<FCacheKey> DebugMissedCacheKeys;
	TUniquePtr<struct FRequestPool> GetRequestPools[2];
	TUniquePtr<struct FRequestPool> PutRequestPools[2];
	TUniquePtr<struct FHttpAccessToken> Access;
	bool bIsUsable;
	bool bReadOnly;
	uint32 FailedLoginAttempts;
	ESpeedClass SpeedClass;
	EBackendLegacyMode LegacyMode;
	static inline FHttpCacheStore* AnyInstance = nullptr;

	struct FValueDebugContext
	{
		FStringView Name;
		const FCacheKey& Key;
		FString Id;
	};

	bool IsServiceReady();
	bool AcquireAccessToken();
	bool ShouldRetryOnError(int64 ResponseCode);
	bool ShouldSimulateMiss(const TCHAR* InKey);
	bool ShouldSimulateMiss(const FCacheKey& Key);

	bool PutCacheRecord(FStringView Name, const FCacheRecord& Record, const FCacheRecordPolicy& Policy, uint64& OutWriteSize);
	uint64 PutRef(const FCbPackage& Package, const FCacheKey& Key, FStringView Bucket, bool bFinalize, TArray<FIoHash>& OutNeededBlobHashes, bool& bOutPutCompletedSuccessfully);

	FOptionalCacheRecord GetCacheRecordOnly(
		FStringView Name,
		const FCacheKey& Key,
		const FCacheRecordPolicy& Policy);
	FOptionalCacheRecord GetCacheRecord(
		FStringView Name,
		const FCacheKey& Key,
		const FCacheRecordPolicy& Policy,
		EStatus& OutStatus);

	bool PutCacheValue(
		FStringView Name,
		const FCacheKey& Key,
		const FValue& Value,
		ECachePolicy Policy,
		uint64& OutWriteSize);

	bool GetCacheValue(
		FStringView Name,
		const FCacheKey& Key,
		ECachePolicy Policy,
		FValue& OutValue,
		FHttpRequest* ExistingHttpRequest = nullptr);

	template<typename ValueType, typename ValueHashGetterType, typename ValueDebugContextGetterType>
	TBitArray<> TryGetCachedDataBatch(
		TConstArrayView<ValueType> Values,
		TArray<FCompressedBuffer>& OutBuffers,
		ValueHashGetterType ValueHashGetter,
		ValueDebugContextGetterType ValueDebugContextGetter,
		FHttpRequest* ExistingHttpRequest = nullptr);
	template<typename ValueType, typename ValueHashGetterType, typename ValueDebugContextGetterType>
	TBitArray<> CachedDataProbablyExistsBatch(
		TConstArrayView<ValueType> Values,
		ValueHashGetterType ValueHashGetter,
		ValueDebugContextGetterType ValueDebugContextGetter,
		FHttpRequest* ExistingHttpRequest = nullptr);
	template<typename ValueRefType, typename ValueRefKeyGetterType, typename ValueRefDebugContextGetterType>
	TArray<FValue> RefCachedDataProbablyExistsBatch(
		TConstArrayView<ValueRefType> ValueRefs,
		ValueRefKeyGetterType ValueRefKeyGetter,
		ValueRefDebugContextGetterType ValueRefDebugContextGetter,
		FHttpRequest* ExistingHttpRequest = nullptr);
};

FHttpCacheStore::FHttpCacheStore(
	const TCHAR* InServiceUrl, 
	bool bResolveHostCanonicalName,
	const TCHAR* InNamespace, 
	const TCHAR* InStructuredNamespace, 
	const TCHAR* InOAuthProvider,
	const TCHAR* InOAuthClientId,
	const TCHAR* InOAuthSecret,
	const TCHAR* InOAuthScope,
	const EBackendLegacyMode InLegacyMode,
	const bool bInReadOnly)
	: Domain(InServiceUrl)
	, Namespace(InNamespace)
	, StructuredNamespace(InStructuredNamespace)
	, DefaultBucket(TEXT("default"))
	, OAuthProvider(InOAuthProvider)
	, OAuthClientId(InOAuthClientId)
	, OAuthSecret(InOAuthSecret)
	, OAuthScope(InOAuthScope)
	, Access(nullptr)
	, bIsUsable(false)
	, bReadOnly(bInReadOnly)
	, FailedLoginAttempts(0)
	, SpeedClass(ESpeedClass::Slow)
	, LegacyMode(InLegacyMode)
{
#if WITH_DATAREQUEST_HELPER
	FDataRequestHelper::StaticInitialize();
#endif
	if (IsServiceReady() && AcquireAccessToken())
	{
		FString EffectiveDomain;
		FString OriginalDomainPrefix;
		TAnsiStringBuilder<64> DomainResolveName;

		if (Domain.StartsWith(TEXT("http://")))
		{
			DomainResolveName << Domain.RightChop(7);
			OriginalDomainPrefix = TEXT("http://");
		}
		else if (Domain.StartsWith(TEXT("https://")))
		{
			DomainResolveName << Domain.RightChop(8);
			OriginalDomainPrefix = TEXT("https://");
		}
		else
		{
			DomainResolveName << Domain;
		}

		addrinfo* AddrResult = nullptr;
		addrinfo AddrHints;
		FMemory::Memset(&AddrHints, 0, sizeof(AddrHints));
		AddrHints.ai_flags = AI_CANONNAME;
		AddrHints.ai_family = AF_UNSPEC;
		if (bResolveHostCanonicalName && !::getaddrinfo(*DomainResolveName, nullptr, &AddrHints, &AddrResult))
		{
			if (AddrResult->ai_canonname)
			{
				// Swap the domain with a canonical name from DNS so that if we are using regional redirection, we pin to a region.
				EffectiveDomain = OriginalDomainPrefix + ANSI_TO_TCHAR(AddrResult->ai_canonname);

				UE_LOG(LogDerivedDataCache, Display,
					TEXT("%s: Pinned to %s based on DNS canonical name."),
					*Domain, *EffectiveDomain);
			}
			else
			{
				EffectiveDomain = Domain;
			}

			::freeaddrinfo(AddrResult);
		}
		else
		{
			EffectiveDomain = Domain;
		}

		GetRequestPools[0] = MakeUnique<FRequestPool>(*Domain, *EffectiveDomain, Access.Get(), UE_HTTPDDC_GET_REQUEST_POOL_SIZE);
		GetRequestPools[1] = MakeUnique<FRequestPool>(*Domain, *EffectiveDomain, Access.Get(), 1);
		PutRequestPools[0] = MakeUnique<FRequestPool>(*Domain, *EffectiveDomain, Access.Get(), UE_HTTPDDC_PUT_REQUEST_POOL_SIZE);
		PutRequestPools[1] = MakeUnique<FRequestPool>(*Domain, *EffectiveDomain, Access.Get(), 1);
		bIsUsable = true;
	}

	AnyInstance = this;
}

FHttpCacheStore::~FHttpCacheStore()
{
	if (AnyInstance == this)
	{
		AnyInstance = nullptr;
	}
#if WITH_DATAREQUEST_HELPER
	FDataRequestHelper::StaticShutdown();
#endif
}

FString FHttpCacheStore::GetName() const
{
	return Domain;
}

TBitArray<> FHttpCacheStore::TryToPrefetch(TConstArrayView<FString> CacheKeys)
{
	return CachedDataProbablyExistsBatch(CacheKeys);
}

bool FHttpCacheStore::WouldCache(const TCHAR* CacheKey, TArrayView<const uint8> InData)
{
	return IsWritable();
}

FHttpCacheStore::ESpeedClass FHttpCacheStore::GetSpeedClass() const
{
	return SpeedClass;
}

bool FHttpCacheStore::ApplyDebugOptions(FBackendDebugOptions& InOptions)
{
	DebugOptions = InOptions;
	return true;
}


bool FHttpCacheStore::IsServiceReady()
{
	FHttpRequest Request(*Domain, *Domain, nullptr, false);
	FHttpRequest::Result Result = Request.PerformBlockingDownload(TEXT("health/ready"), nullptr);
	
	if (Result == FHttpRequest::Success && Request.GetResponseCode() == 200)
	{
		UE_LOG(LogDerivedDataCache, Display, TEXT("%s: HTTP DDC service status: %s."), *Request.GetName(), *Request.GetResponseAsString());
		return true;
	}
	else
	{
		UE_LOG(LogDerivedDataCache, Warning, TEXT("%s: Unable to reach HTTP DDC service at %s. Status: %d . Response: %s"), *Request.GetName(), *Domain, Request.GetResponseCode(), *Request.GetResponseAsString());
	}

	return false;
}

bool FHttpCacheStore::AcquireAccessToken()
{
	if (Domain.StartsWith(TEXT("http://localhost")))
	{
		UE_LOG(LogDerivedDataCache, Log, TEXT("Connecting to a local host '%s', so skipping authorization"), *Domain);
		return true;
	}

	// Avoid spamming the this if the service is down
	if (FailedLoginAttempts > UE_HTTPDDC_MAX_FAILED_LOGIN_ATTEMPTS)
	{
		return false;
	}

	ensureMsgf(OAuthProvider.StartsWith(TEXT("http://")) || OAuthProvider.StartsWith(TEXT("https://")),
		TEXT("The OAuth provider %s is not valid. Needs to be a fully qualified url."),
		*OAuthProvider
	);

	// In case many requests wants to update the token at the same time
	// get the current serial while we wait to take the CS.
	const uint32 WantsToUpdateTokenSerial = Access.IsValid() ? Access->GetSerial() : 0u;

	{
		FScopeLock Lock(&AccessCs);

		// Check if someone has beaten us to update the token, then it 
		// should now be valid.
		if (Access.IsValid() && Access->GetSerial() > WantsToUpdateTokenSerial)
		{
			return true;
		}

		const uint32 SchemeEnd = OAuthProvider.Find(TEXT("://")) + 3;
		const uint32 DomainEnd = OAuthProvider.Find(TEXT("/"), ESearchCase::CaseSensitive, ESearchDir::FromStart, SchemeEnd);
		FString AuthDomain(DomainEnd, *OAuthProvider);
		FString Uri(*OAuthProvider + DomainEnd + 1);

		FHttpRequest Request(*AuthDomain, *AuthDomain, nullptr, false);
		FHttpRequest::Result Result = FHttpRequest::Success;
		if (OAuthProvider.StartsWith(TEXT("http://localhost")))
		{
			// Simple unauthenticated call to a local endpoint that mimics
			// the result from an OIDC provider.
			Result = Request.PerformBlockingDownload(*Uri, nullptr);
		}
		else
		{
			// Needs client id and secret to authenticate with an actual OIDC provider.

			// If contents of the secret string is a file path, resolve and read form data.
			if (OAuthSecret.StartsWith(TEXT("file://")))
			{
				FString FilePath = OAuthSecret.Mid(7, OAuthSecret.Len() - 7);
					FString SecretFileContents;
				if (FFileHelper::LoadFileToString(SecretFileContents, *FilePath))
				{
					// Overwrite the filepath with the actual content.
					OAuthSecret = SecretFileContents;
				}
				else
				{
					UE_LOG(LogDerivedDataCache, Warning, TEXT("%s: Failed to read OAuth form data file (%s)."), *Request.GetName(), *OAuthSecret);
					return false;
				}
			}

			FString OAuthFormData = FString::Printf(
				TEXT("client_id=%s&scope=%s&grant_type=client_credentials&client_secret=%s"),
				*OAuthClientId,
				*OAuthScope,
				*OAuthSecret
			);

			TArray<uint8> FormData;
			auto OAuthFormDataUTF8 = FTCHARToUTF8(*OAuthFormData);
			FormData.Append((uint8*)OAuthFormDataUTF8.Get(), OAuthFormDataUTF8.Length());

			Result = Request.PerformBlockingUpload<FHttpRequest::Post>(*Uri, MakeArrayView(FormData));
		}

		if (Result == FHttpRequest::Success && Request.GetResponseCode() == 200)
		{
			TSharedPtr<FJsonObject> ResponseObject = Request.GetResponseAsJsonObject();
			if (ResponseObject)
			{
				FString AccessTokenString;
				int32 ExpiryTimeSeconds = 0;
				int32 CurrentTimeSeconds = int32(FPlatformTime::ToSeconds(FPlatformTime::Cycles()));

				if (ResponseObject->TryGetStringField(TEXT("access_token"), AccessTokenString) &&
					ResponseObject->TryGetNumberField(TEXT("expires_in"), ExpiryTimeSeconds))
				{
					if (!Access)
					{
						Access = MakeUnique<FHttpAccessToken>();
					}
					Access->SetHeader(*AccessTokenString);
					UE_LOG(LogDerivedDataCache, Display, TEXT("%s: Logged in to HTTP DDC services. Expires in %d seconds."), *Request.GetName(), ExpiryTimeSeconds);

					//Schedule a refresh of the token ahead of expiry time (this will not work in commandlets)
					if (!IsRunningCommandlet())
					{
						FTSTicker::GetCoreTicker().AddTicker(FTickerDelegate::CreateLambda(
							[this](float DeltaTime)
							{
								this->AcquireAccessToken();
								return false;
							}
						), ExpiryTimeSeconds - 20.0f);
					}
					// Reset failed login attempts, the service is indeed alive.
					FailedLoginAttempts = 0;
					return true;
				}
			}
		}
		else
		{
			UE_LOG(LogDerivedDataCache, Warning, TEXT("%s: Failed to log in to HTTP services. Server responed with code %d."), *Request.GetName(), Request.GetResponseCode());
			FailedLoginAttempts++;
		}
	}
	return false;
}

bool FHttpCacheStore::ShouldRetryOnError(int64 ResponseCode)
{
	// Access token might have expired, request a new token and try again.
	if (ResponseCode == 401 && AcquireAccessToken())
	{
		return true;
	}

	// Too many requests, make a new attempt
	if (ResponseCode == 429)
	{
		return true;
	}

	return false;
}

bool FHttpCacheStore::ShouldSimulateMiss(const TCHAR* InKey)
{
	if (DebugOptions.RandomMissRate == 0 && DebugOptions.SimulateMissTypes.IsEmpty())
	{
		return false;
	}

	const FName Key(InKey);
	const uint32 Hash = GetTypeHash(Key);

	if (FScopeLock Lock(&MissedKeysCS); DebugMissedKeys.ContainsByHash(Hash, Key))
	{
		return true;
	}

	if (DebugOptions.ShouldSimulateMiss(InKey))
	{
		FScopeLock Lock(&MissedKeysCS);
		DebugMissedKeys.AddByHash(Hash, Key);
		return true;
	}

	return false;
}

bool FHttpCacheStore::ShouldSimulateMiss(const FCacheKey& Key)
{
	if (DebugOptions.RandomMissRate == 0 && DebugOptions.SimulateMissTypes.IsEmpty())
	{
		return false;
	}

	const uint32 Hash = GetTypeHash(Key);

	if (FScopeLock Lock(&MissedKeysCS); DebugMissedCacheKeys.ContainsByHash(Hash, Key))
	{
		return true;
	}

	if (DebugOptions.ShouldSimulateMiss(Key))
	{
		FScopeLock Lock(&MissedKeysCS);
		DebugMissedCacheKeys.AddByHash(Hash, Key);
		return true;
	}

	return false;
}

uint64 FHttpCacheStore::PutRef(const FCbPackage& Package, const FCacheKey& Key, FStringView Bucket, bool bFinalize, TArray<FIoHash>& OutNeededBlobHashes, bool& bOutPutCompletedSuccessfully)
{
	bOutPutCompletedSuccessfully = false;

	uint64 BytesSent = 0;
	TStringBuilder<256> RefsUri;
	RefsUri << "api/v1/refs/" << StructuredNamespace << "/" << Bucket << "/" << Key.Hash;
	if (bFinalize)
	{
		RefsUri << "/finalize/" << Package.GetObjectHash();
	}

	int64 ResponseCode = 0;
	for (uint32 Attempts = 0; (Attempts < UE_HTTPDDC_MAX_ATTEMPTS) && !ShouldAbortForShutdown() && (Attempts == 0 || ShouldRetryOnError(ResponseCode)); ++Attempts)
	{
		FScopedRequestPtr Request(PutRequestPools[IsInGameThread()].Get());

		if (bFinalize)
		{
			Request->PerformBlockingUpload<FHttpRequest::Post>(*RefsUri, TArrayView<const uint8>());
		}
		else
		{
			Request->SetHeader(TEXT("X-Jupiter-IoHash"), *WriteToString<48>(Package.GetObjectHash()));
			Request->PerformBlockingUpload<FHttpRequest::PutCompactBinary>(*RefsUri, MakeConstArrayView(Package.GetObject().GetBuffer().ToShared()));
		}
		ResponseCode = Request->GetResponseCode();

		if (FHttpRequest::IsSuccessResponse(ResponseCode))
		{
			BytesSent += Request->GetBytesSent();

			// Useful when debugging issues related to compressed/uncompressed blobs being returned from Jupiter
			const bool bPutRefBlobsAlways = false;

			if (bPutRefBlobsAlways && !bFinalize)
			{
				Package.GetObject().IterateAttachments([&OutNeededBlobHashes](FCbFieldView AttachmentFieldView)
					{
						FIoHash AttachmentHash = AttachmentFieldView.AsHash();
						if (!AttachmentHash.IsZero())
						{
							OutNeededBlobHashes.Add(AttachmentHash);
						}
					});
			}
			else if (TSharedPtr<FJsonObject> ResponseObject = Request->GetResponseAsJsonObject())
			{
				TArray<FString> NeedsArrayStrings;
				ResponseObject->TryGetStringArrayField(TEXT("needs"), NeedsArrayStrings);

				OutNeededBlobHashes.Empty(NeedsArrayStrings.Num());
				for (const FString& NeededString : NeedsArrayStrings)
				{
					FIoHash BlobHash;
					LexFromString(BlobHash, *NeededString);
					if (!BlobHash.IsZero())
					{
						OutNeededBlobHashes.Add(BlobHash);
					}
				}
			}
			else
			{
				OutNeededBlobHashes.Empty();
			}

			bOutPutCompletedSuccessfully = true;
			break;
		}
		else
		{
			OutNeededBlobHashes.Empty();
		}
	}

	return BytesSent;
}

bool FHttpCacheStore::PutCacheRecord(
	FStringView Name,
	const FCacheRecord& Record,
	const FCacheRecordPolicy& Policy,
	uint64& OutWriteSize)
{
	OutWriteSize = 0;

	if (!IsWritable())
	{
		UE_LOG(LogDerivedDataCache, VeryVerbose,
			TEXT("%s: Skipped put of %s from '%.*s' because this cache store is read-only"),
			*GetName(), *WriteToString<96>(Record.GetKey()), Name.Len(), Name.GetData());
		return false;
	}

	const FCacheKey& Key = Record.GetKey();
	const ECachePolicy RecordPolicy = Policy.GetRecordPolicy();

	// Skip the request if storing to the cache is disabled.
	// Http backends won't generally be "local" but including handling for this possibility for consistency
	const ECachePolicy StoreFlag = SpeedClass == ESpeedClass::Local ? ECachePolicy::StoreLocal : ECachePolicy::StoreRemote;
	if (!EnumHasAnyFlags(RecordPolicy, StoreFlag))
	{
		UE_LOG(LogDerivedDataCache, VeryVerbose, TEXT("%s: Skipped put of %s from '%.*s' due to cache policy"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return false;
	}

	if (ShouldSimulateMiss(Key))
	{
		UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s: Simulated miss for put of %s from '%.*s'"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return false;
	}

	// TODO: Jupiter currently always overwrites.  It doesn't have a "write if not present" feature (for records or attachments),
	//		 but would require one to implement all policy correctly.

	FString Bucket(Key.Bucket.ToString());
	Bucket.ToLowerInline();

	bool bPutCompletedSuccessfully = false;

	FCbPackage Package = Record.Save();
	TArray<FIoHash> NeededBlobHashes;

	// Initial record upload
	size_t PutRefBytesSent = PutRef(Package, Record.GetKey(), Bucket, false, NeededBlobHashes, bPutCompletedSuccessfully);
	OutWriteSize += PutRefBytesSent;

	if (!bPutCompletedSuccessfully)
	{
		UE_LOG(LogDerivedDataCache, Log, TEXT("%s: Failed to put reference object for put of %s from '%.*s'"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return false;
	}

	// TODO: blob uploading and finalization should be replaced with a single batch compressed blob upload endpoint in the future.
	TStringBuilder<128> ExpectedHashes;
	bool bExpectedHashesSerialized = false;

	// Needed blob upload (if any missing)
	for (const FIoHash& NeededBlobHash : NeededBlobHashes)
	{
		TStringBuilder<256> CompressedBlobsUri;
		CompressedBlobsUri << "api/v1/compressed-blobs/" << StructuredNamespace << "/" << NeededBlobHash;

		if (const FCbAttachment* Attachment = Package.FindAttachment(NeededBlobHash))
		{
			FSharedBuffer TempBuffer;
			TConstArrayView<uint8> BlobArrayView;
			if (Attachment->IsCompressedBinary())
			{
				TempBuffer = Attachment->AsCompressedBinary().GetCompressed().ToShared();
				BlobArrayView = MakeConstArrayView(TempBuffer);
			}
			else if (Attachment->IsBinary())
			{
				TempBuffer = FCompressedBuffer::Compress(Attachment->AsCompositeBinary()).GetCompressed().ToShared();
				BlobArrayView = MakeConstArrayView(TempBuffer);
			}
			else
			{
				TempBuffer = FCompressedBuffer::Compress(Attachment->AsObject().GetBuffer()).GetCompressed().ToShared();
				BlobArrayView = MakeConstArrayView(TempBuffer);
			}

			int64 ResponseCode = 0;
			for (uint32 Attempts = 0; (Attempts < UE_HTTPDDC_MAX_ATTEMPTS) && !ShouldAbortForShutdown() && (Attempts == 0 || ShouldRetryOnError(ResponseCode)); ++Attempts)
			{
				FScopedRequestPtr Request(PutRequestPools[IsInGameThread()].Get());
				Request->PerformBlockingUpload<FHttpRequest::PutCompressedBlob>(*CompressedBlobsUri, BlobArrayView);

				ResponseCode = Request->GetResponseCode();

				if (FHttpRequest::IsSuccessResponse(ResponseCode))
				{
					OutWriteSize += Request->GetBytesSent();
					break;
				}
			}
		}
		else
		{
			if (!bExpectedHashesSerialized)
			{
				bool bFirstHash = true;
				for (const FCbAttachment& PackageAttachment : Package.GetAttachments())
				{
					if (!bFirstHash)
					{
						ExpectedHashes << TEXT(", ");
					}
					ExpectedHashes << PackageAttachment.GetHash();
					bFirstHash = false;
				}
				bExpectedHashesSerialized = true;
			}
			UE_LOG(LogDerivedDataCache, Log, TEXT("%s: Server reported needed hash '%s' that is outside the set of expected hashes (%s) for put of %s from '%.*s'"),
				*GetName(), *WriteToString<96>(NeededBlobHash), ExpectedHashes.ToString(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		}
	}

	// Finalization (if any blobs needed)
	if (!NeededBlobHashes.IsEmpty())
	{
		size_t FinalizeRefBytesSent = PutRef(Package, Record.GetKey(), Bucket, true, NeededBlobHashes, bPutCompletedSuccessfully);
		OutWriteSize += FinalizeRefBytesSent;
	}

	return bPutCompletedSuccessfully && NeededBlobHashes.IsEmpty();
}

FOptionalCacheRecord FHttpCacheStore::GetCacheRecordOnly(
	const FStringView Name,
	const FCacheKey& Key,
	const FCacheRecordPolicy& Policy)
{
	if (!IsUsable())
	{
		UE_LOG(LogDerivedDataCache, VeryVerbose,
			TEXT("%s: Skipped get of %s from '%.*s' because this cache store is not available"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return FOptionalCacheRecord();
	}

	// Skip the request if querying the cache is disabled.
	const ECachePolicy QueryPolicy = SpeedClass == ESpeedClass::Local
		? ECachePolicy::QueryLocal : ECachePolicy::QueryRemote;
	if (!EnumHasAnyFlags(Policy.GetRecordPolicy(), QueryPolicy))
	{
		UE_LOG(LogDerivedDataCache, VeryVerbose, TEXT("%s: Skipped get of %s from '%.*s' due to cache policy"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return FOptionalCacheRecord();
	}

	if (ShouldSimulateMiss(Key))
	{
		UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s: Simulated miss for get of %s from '%.*s'"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return FOptionalCacheRecord();
	}

	FScopedRequestPtr Request(GetRequestPools[IsInGameThread()].Get());

	FOptionalCacheRecord Record;
	{
		FString Bucket(Key.Bucket.ToString());
		Bucket.ToLowerInline();

		TStringBuilder<256> RefsUri;
		RefsUri << "api/v1/refs/" << StructuredNamespace << "/" << Bucket << "/" << Key.Hash;

		bool bIsSuccessfulResponse = false;
		FSharedBuffer ResponseBuffer;
		int64 ResponseCode = 0;
		for (uint32 Attempts = 0; (Attempts < UE_HTTPDDC_MAX_ATTEMPTS) && !ShouldAbortForShutdown() && (Attempts == 0 || ShouldRetryOnError(ResponseCode)); ++Attempts)
		{
			if (Attempts > 0)
			{
				Request->Reset();
			}

			TArray<uint8> ByteArray;
			Request->SetHeader(TEXT("Accept"), TEXT("application/x-ue-cb"));
			Request->PerformBlockingDownload(*RefsUri, &ByteArray, {401, 404});
			ResponseCode = Request->GetResponseCode();

			if (FHttpRequest::IsSuccessResponse(ResponseCode))
			{
				ResponseBuffer = MakeSharedBufferFromArray(MoveTemp(ByteArray));
				bIsSuccessfulResponse = true;
				break;
			}
		}

		if (!bIsSuccessfulResponse)
		{
			UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s: Cache miss with missing package for %s from '%.*s'"),
				*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
			return Record;
		}

		if (ValidateCompactBinary(ResponseBuffer, ECbValidateMode::Default) != ECbValidateError::None)
		{
			UE_LOG(LogDerivedDataCache, Display, TEXT("%s: Cache miss with invalid package for %s from '%.*s'"),
				*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
			return Record;
		}

		Record = FCacheRecord::Load(FCbPackage(FCbObject(ResponseBuffer)));
		if (Record.IsNull())
		{
			UE_LOG(LogDerivedDataCache, Display, TEXT("%s: Cache miss with record load failure for %s from '%.*s'"),
				*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
			return Record;
		}
	}

	return Record;
}

bool FHttpCacheStore::PutCacheValue(
	const FStringView Name,
	const FCacheKey& Key,
	const FValue& Value,
	const ECachePolicy Policy,
	uint64& OutWriteSize)
{
	if (!IsWritable())
	{
		UE_LOG(LogDerivedDataCache, VeryVerbose,
			TEXT("%s: Skipped put of %s from '%.*s' because this cache store is read-only"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return false;
	}

	// Skip the request if storing to the cache is disabled.
	const ECachePolicy StoreFlag = SpeedClass == ESpeedClass::Local ? ECachePolicy::StoreLocal : ECachePolicy::StoreRemote;
	if (!EnumHasAnyFlags(Policy, StoreFlag))
	{
		UE_LOG(LogDerivedDataCache, VeryVerbose, TEXT("%s: Skipped put of %s from '%.*s' due to cache policy"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return false;
	}

	if (ShouldSimulateMiss(Key))
	{
		UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s: Simulated miss for put of %s from '%.*s'"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return false;
	}

	// TODO: Jupiter currently always overwrites.  It doesn't have a "write if not present" feature (for records or attachments),
	//		 but would require one to implement all policy correctly.

	FString Bucket(Key.Bucket.ToString());
	Bucket.ToLowerInline();

	bool bPutCompletedSuccessfully = false;

	FCbWriter Writer;
	Writer.BeginObject();
	Writer.AddBinaryAttachment("RawHash", Value.GetRawHash());
	Writer.AddInteger("RawSize", Value.GetRawSize());
	Writer.EndObject();

	FCbPackage Package(Writer.Save().AsObject());
	TArray<FIoHash> NeededBlobHashes;

	// Initial record upload
	size_t PutRefBytesSent = PutRef(Package, Key, Bucket, false, NeededBlobHashes, bPutCompletedSuccessfully);
	OutWriteSize += PutRefBytesSent;

	if (!bPutCompletedSuccessfully)
	{
		UE_LOG(LogDerivedDataCache, Log, TEXT("%s: Failed to put reference object for put of %s from '%.*s'"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return false;
	}

	// Needed blob upload (if any missing)
	if (!NeededBlobHashes.IsEmpty())
	{
		if (NeededBlobHashes.Num() != 1)
		{
			TStringBuilder<128> NeededHashString;
			bool bFirstHash = true;
			for (const FIoHash& NeededBlobHash : NeededBlobHashes)
			{
				if (!bFirstHash)
				{
					NeededHashString << TEXT(", ");
				}
				NeededHashString << NeededBlobHash;
				bFirstHash = false;
			}

			UE_LOG(LogDerivedDataCache, Log, TEXT("%s: Server reported unexpected needed hash quantity '%d' (%s) for put of %s from '%.*s'"),
				*GetName(), NeededBlobHashes.Num(), NeededHashString.ToString(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
			return false;
		}

		if (NeededBlobHashes[0] != Value.GetRawHash())
		{
			UE_LOG(LogDerivedDataCache, Log, TEXT("%s: Server reported needed hash '%s' that is outside the set of expected hashes (%s) for put of %s from '%.*s'"),
				*GetName(), *WriteToString<96>(NeededBlobHashes[0]), *WriteToString<96>(Value.GetRawHash()), *WriteToString<96>(Key), Name.Len(), Name.GetData());
			return false;
		}

		TStringBuilder<256> CompressedBlobsUri;
		CompressedBlobsUri << "api/v1/compressed-blobs/" << StructuredNamespace << "/" << Value.GetRawHash();

		FSharedBuffer TempBuffer = Value.GetData().GetCompressed().ToShared();
		FScopedRequestPtr Request(PutRequestPools[IsInGameThread()].Get());

		int64 ResponseCode = 0;
		for (uint32 Attempts = 0; (Attempts < UE_HTTPDDC_MAX_ATTEMPTS) && !ShouldAbortForShutdown() && (Attempts == 0 || ShouldRetryOnError(ResponseCode)); ++Attempts)
		{
			if (Attempts > 0)
			{
				Request->Reset();
			}

			Request->PerformBlockingUpload<FHttpRequest::PutCompressedBlob>(*CompressedBlobsUri, MakeConstArrayView(TempBuffer));

			ResponseCode = Request->GetResponseCode();

			if (FHttpRequest::IsSuccessResponse(ResponseCode))
			{
				OutWriteSize += Request->GetBytesSent();
				break;
			}
		}

		OutWriteSize += PutRef(Package, Key, Bucket, true, NeededBlobHashes, bPutCompletedSuccessfully);
	}


	return bPutCompletedSuccessfully && NeededBlobHashes.IsEmpty();
}

bool FHttpCacheStore::GetCacheValue(
	const FStringView Name,
	const FCacheKey& Key,
	const ECachePolicy Policy,
	FValue& OutValue,
	FHttpRequest* ExistingHttpRequest)
{
	if (!IsUsable())
	{
		UE_LOG(LogDerivedDataCache, VeryVerbose,
			TEXT("%s: Skipped get of %s from '%.*s' because this cache store is not available"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return false;
	}

	// Skip the request if querying the cache is disabled.
	const ECachePolicy QueryFlag = SpeedClass == ESpeedClass::Local ? ECachePolicy::QueryLocal : ECachePolicy::QueryRemote;
	if (!EnumHasAnyFlags(Policy, QueryFlag))
	{
		UE_LOG(LogDerivedDataCache, VeryVerbose, TEXT("%s: Skipped get of %s from '%.*s' due to cache policy"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return false;
	}

	if (ShouldSimulateMiss(Key))
	{
		UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s: Simulated miss for get of %s from '%.*s'"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return false;
	}

	const bool bSkipData = EnumHasAnyFlags(Policy, ECachePolicy::SkipData);

	FString Bucket(Key.Bucket.ToString());
	Bucket.ToLowerInline();

	TStringBuilder<256> RefsUri;
	RefsUri << "api/v1/refs/" << StructuredNamespace << "/" << Bucket << "/" << Key.Hash;

	FHttpRequest* Request = ExistingHttpRequest;
	TOptional<FScopedRequestPtr> RequestPoolRequest;
	if (Request == nullptr)
	{
		RequestPoolRequest.Emplace(GetRequestPools[IsInGameThread()].Get());
		Request = RequestPoolRequest->Get();
	}
	else
	{
		Request->Reset();
	}

	bool bIsSuccessfulResponse = false;
	FSharedBuffer ResponseBuffer;
	int64 ResponseCode = 0;
	for (uint32 Attempts = 0; (Attempts < UE_HTTPDDC_MAX_ATTEMPTS) && !ShouldAbortForShutdown() && (Attempts == 0 || ShouldRetryOnError(ResponseCode)); ++Attempts)
	{
		if (Attempts > 0)
		{
			Request->Reset();
		}

		TArray<uint8> ByteArray;
		if (bSkipData)
		{
			Request->SetHeader(TEXT("Accept"), TEXT("application/x-ue-cb"));
		}
		else
		{
			Request->SetHeader(TEXT("Accept"), TEXT("application/x-jupiter-inline"));
		}
		Request->PerformBlockingDownload(*RefsUri, &ByteArray, { 401, 404 });
		ResponseCode = Request->GetResponseCode();

		if (FHttpRequest::IsSuccessResponse(ResponseCode))
		{
			ResponseBuffer = MakeSharedBufferFromArray(MoveTemp(ByteArray));
			bIsSuccessfulResponse = true;
			break;
		}
	}

	if (!bIsSuccessfulResponse)
	{
		UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s: Cache miss with missing package for %s from '%.*s'"),
			*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
		return false;
	}

	if (bSkipData)
	{
		if (ValidateCompactBinary(ResponseBuffer, ECbValidateMode::Default) != ECbValidateError::None)
		{
			UE_LOG(LogDerivedDataCache, Display, TEXT("%s: Cache miss with invalid package for %s from '%.*s'"),
				*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
			return false;
		}

		const FCbObjectView Object = FCbObject(ResponseBuffer);
		const FIoHash RawHash = Object["RawHash"].AsHash();
		const uint64 RawSize = Object["RawSize"].AsUInt64(MAX_uint64);
		if (RawHash.IsZero() || RawSize == MAX_uint64)
		{
			UE_LOG(LogDerivedDataCache, Display, TEXT("%s: Cache miss with invalid value for %s from '%.*s'"),
				*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
			return false;
		}
		OutValue = FValue(RawHash, RawSize);
	}
	else
	{
		FCompressedBuffer CompressedBuffer = FCompressedBuffer::FromCompressed(ResponseBuffer);
		if (!CompressedBuffer)
		{
			FString ReceivedHashStr;
			if (Request->GetHeader("X-Jupiter-InlinePayloadHash", ReceivedHashStr))
			{
				FIoHash ReceivedHash(ReceivedHashStr);
				FIoHash ComputedHash = FIoHash::HashBuffer(ResponseBuffer.GetView());
				if (ReceivedHash == ComputedHash)
				{
					CompressedBuffer = FCompressedBuffer::Compress(ResponseBuffer);
				}
			}
		}

		if (!CompressedBuffer)
		{
			UE_LOG(LogDerivedDataCache, Display, TEXT("%s: Cache miss with invalid package for %s from '%.*s'"),
				*GetName(), *WriteToString<96>(Key), Name.Len(), Name.GetData());
			return false;
		}
		OutValue = FValue(CompressedBuffer);
	}

	return true;
}

FOptionalCacheRecord FHttpCacheStore::GetCacheRecord(
	const FStringView Name,
	const FCacheKey& Key,
	const FCacheRecordPolicy& Policy,
	EStatus& OutStatus)
{
	FOptionalCacheRecord Record = GetCacheRecordOnly(Name, Key, Policy);
	if (Record.IsNull())
	{
		OutStatus = EStatus::Error;
		return Record;
	}

	OutStatus = EStatus::Ok;

	FCacheRecordBuilder RecordBuilder(Key);

	if (!EnumHasAnyFlags(Policy.GetRecordPolicy(), ECachePolicy::SkipMeta))
	{
		RecordBuilder.SetMeta(FCbObject(Record.Get().GetMeta()));
	}

	// TODO: There is not currently a batched GET endpoint for Jupiter.  Once there is, all payload data should be fetched in one call.
	//		 In the meantime, we try to keep the code structured in a way that is friendly to future batching of GETs.

	TArray<FValueWithId> RequiredGets;
	TArray<FValueWithId> RequiredHeads;

	for (FValueWithId Value : Record.Get().GetValues())
	{
		const ECachePolicy ValuePolicy = Policy.GetValuePolicy(Value.GetId());
		if (IsValueDataReady(Value, ValuePolicy))
		{
			RecordBuilder.AddValue(MoveTemp(Value));
		}
		else
		{
			if (EnumHasAnyFlags(ValuePolicy, ECachePolicy::SkipData))
			{
				RequiredHeads.Emplace(Value);
			}
			else
			{
				RequiredGets.Emplace(Value);
			}
		}
	}

	auto HashGetter = [](const FValueWithId& Value)
	{
		return Value.GetRawHash();
	};

	auto DebugContextGetter = [Name, &Key](const FValueWithId& Value)
	{
		return FValueDebugContext{ Name, Key, FString(*WriteToString<16>(Value.GetId())) };
	};

	if (CachedDataProbablyExistsBatch<FValueWithId>(RequiredHeads, HashGetter, DebugContextGetter).CountSetBits() != RequiredHeads.Num())
	{
		OutStatus = EStatus::Error;
		return FOptionalCacheRecord();
	}

	TArray<FCompressedBuffer> FetchedBuffers;
	if (TryGetCachedDataBatch<FValueWithId>(RequiredGets, FetchedBuffers, HashGetter, DebugContextGetter).CountSetBits() != RequiredGets.Num())
	{
		OutStatus = EStatus::Error;
		return FOptionalCacheRecord();
	}

	for (int32 Index = 0; Index < RequiredHeads.Num(); ++Index)
	{
		RecordBuilder.AddValue(RequiredHeads[Index].RemoveData());
	}

	for (int32 Index = 0; Index < RequiredGets.Num(); ++Index)
	{
		RecordBuilder.AddValue(FValueWithId(RequiredGets[Index].GetId(), FetchedBuffers[Index]));
	}

	return RecordBuilder.Build();
}

template<typename ValueType, typename ValueHashGetterType, typename ValueDebugContextGetterType>
TBitArray<> FHttpCacheStore::TryGetCachedDataBatch(
	TConstArrayView<ValueType> Values,
	TArray<FCompressedBuffer>& OutBuffers,
	ValueHashGetterType ValueHashGetter,
	ValueDebugContextGetterType ValueDebugContextGetter,
	FHttpRequest* ExistingHttpRequest)
{
	FHttpRequest* Request = ExistingHttpRequest;
	TOptional<FScopedRequestPtr> RequestPoolRequest;
	if (Request == nullptr)
	{
		RequestPoolRequest.Emplace(GetRequestPools[IsInGameThread()].Get());
		Request = RequestPoolRequest->Get();
	}
	else
	{
		Request->Reset();
	}

	bool bRequestNeedsReset = false;
	TBitArray<> Results(true, Values.Num());
	int32 ValueIndex = 0;
	for (const ValueType& Value : Values)
	{
		const FIoHash& RawHash = ValueHashGetter(Value);
		TStringBuilder<256> CompressedBlobsUri;
		CompressedBlobsUri << "api/v1/compressed-blobs/" << StructuredNamespace << "/" << RawHash;

		bool bHit = false;
		FCompressedBuffer CompressedBuffer;
		int64 ResponseCode = 0;
		for (uint32 Attempts = 0; (Attempts < UE_HTTPDDC_MAX_ATTEMPTS) && !ShouldAbortForShutdown() && (Attempts == 0 || ShouldRetryOnError(ResponseCode)); ++Attempts)
		{
			if (bRequestNeedsReset)
			{
				Request->Reset();
			}

			TArray<uint8> ByteArray;
			const FHttpRequest::Result Result = Request->PerformBlockingDownload(*CompressedBlobsUri, &ByteArray, {404});
			ResponseCode = Request->GetResponseCode();
			bRequestNeedsReset = true;

			if (FHttpRequest::IsSuccessResponse(ResponseCode))
			{
				CompressedBuffer = FCompressedBuffer::FromCompressed(MakeSharedBufferFromArray(MoveTemp(ByteArray)));
				bHit = true;
				break;
			}
		}

		if (!bHit)
		{
			FValueDebugContext DebugContext = ValueDebugContextGetter(Value);
			UE_LOG(LogDerivedDataCache, Verbose,
				TEXT("%s: Cache miss with missing value %s with hash %s for %s from '%.*s'"),
				*GetName(), *DebugContext.Id, *WriteToString<48>(RawHash), *WriteToString<96>(DebugContext.Key),
				DebugContext.Name.Len(), DebugContext.Name.GetData());
			Results[ValueIndex] = false;
		}
		else if (CompressedBuffer.GetRawHash() != RawHash)
		{
			FValueDebugContext DebugContext = ValueDebugContextGetter(Value);
			UE_LOG(LogDerivedDataCache, Display,
				TEXT("%s: Cache miss with corrupted value %s with hash %s for %s from '%.*s'"),
				*GetName(), *DebugContext.Id, *WriteToString<48>(RawHash),
				*WriteToString<96>(DebugContext.Key), DebugContext.Name.Len(), DebugContext.Name.GetData());
			Results[ValueIndex] = false;
		}
		else
		{
			OutBuffers.Add(CompressedBuffer);
		}
		++ValueIndex;
	}
	return Results;
}

template<typename ValueType, typename ValueHashGetterType, typename ValueDebugContextGetterType>
TBitArray<> FHttpCacheStore::CachedDataProbablyExistsBatch(
	TConstArrayView<ValueType> Values,
	ValueHashGetterType ValueHashGetter,
	ValueDebugContextGetterType ValueDebugContextGetter,
	FHttpRequest* ExistingHttpRequest)
{
	if (Values.IsEmpty())
	{
		return TBitArray<>();
	}

	FHttpRequest* Request = ExistingHttpRequest;
	TOptional<FScopedRequestPtr> RequestPoolRequest;
	if (Request == nullptr)
	{
		RequestPoolRequest.Emplace(GetRequestPools[IsInGameThread()].Get());
		Request = RequestPoolRequest->Get();
	}
	else
	{
		Request->Reset();
	}

	TStringBuilder<256> CompressedBlobsUri;
	CompressedBlobsUri << "api/v1/compressed-blobs/" << StructuredNamespace << "/exists?";
	bool bFirstItem = true;
	for (const ValueType& Value : Values)
	{
		if (!bFirstItem)
		{
			CompressedBlobsUri << "&";
		}
		CompressedBlobsUri << "id=" << ValueHashGetter(Value);
		bFirstItem = false;
	}

	int64 ResponseCode = 0;
	for (uint32 Attempts = 0; (Attempts < UE_HTTPDDC_MAX_ATTEMPTS) && !ShouldAbortForShutdown() && (Attempts == 0 || ShouldRetryOnError(ResponseCode)); ++Attempts)
	{
		if (Attempts > 0)
		{
			Request->Reset();
		}

		TConstArrayView<uint8> DummyBuffer;
		const FHttpRequest::Result Result = Request->PerformBlockingUpload<FHttpRequest::Post>(*CompressedBlobsUri, DummyBuffer);
		ResponseCode = Request->GetResponseCode();

		if (FHttpRequest::IsSuccessResponse(ResponseCode))
		{
			if (TSharedPtr<FJsonObject> ResponseObject = Request->GetResponseAsJsonObject())
			{
				TArray<FString> NeedsArrayStrings;
				if (ResponseObject->TryGetStringArrayField(TEXT("needs"), NeedsArrayStrings))
				{
					if (NeedsArrayStrings.IsEmpty())
					{
						return TBitArray<>(true, Values.Num());
					}
				}

				TBitArray<> Results(true, Values.Num());
				for (const FString& NeedsString : NeedsArrayStrings)
				{
					FIoHash NeedHash;
					LexFromString(NeedHash, *NeedsString);
					for (int32 ValueIndex = 0; ValueIndex < Values.Num(); ++ValueIndex)
					{
						if (NeedHash == ValueHashGetter(Values[ValueIndex]))
						{
							Results[ValueIndex] = false;

							FValueDebugContext DebugContext = ValueDebugContextGetter(Values[ValueIndex]);
							UE_LOG(LogDerivedDataCache, Verbose,
								TEXT("%s: Cache exists miss with missing value %s with hash %s for %s from '%.*s'"),
								*GetName(), *DebugContext.Id, *NeedsString, *WriteToString<96>(DebugContext.Key),
								DebugContext.Name.Len(), DebugContext.Name.GetData());
						}
					}
				}

				return Results;
			}
			else
			{
				UE_LOG(LogDerivedDataCache, Log,
					TEXT("%s: Cache exists returned invalid results."),
					*GetName());
				return TBitArray<>(false, Values.Num());
			}

			return TBitArray<>(false, Values.Num());
		}
	}

	return TBitArray<>(false, Values.Num());
}

template<typename ValueRefType, typename ValueRefKeyGetterType, typename ValueRefDebugContextGetterType>
TArray<FValue> FHttpCacheStore::RefCachedDataProbablyExistsBatch(
	TConstArrayView<ValueRefType> ValueRefs,
	ValueRefKeyGetterType ValueRefKeyGetter,
	ValueRefDebugContextGetterType ValueRefDebugContextGetter,
	FHttpRequest* ExistingHttpRequest)
{
	if (ValueRefs.IsEmpty())
	{
		return TArray<FValue>();
	}

	FHttpRequest* Request = ExistingHttpRequest;
	TOptional<FScopedRequestPtr> RequestPoolRequest;
	if (Request == nullptr)
	{
		RequestPoolRequest.Emplace(GetRequestPools[IsInGameThread()].Get());
		Request = RequestPoolRequest->Get();
	}
	else
	{
		Request->Reset();
	}

	TStringBuilder<256> RefsUri;
	RefsUri << "api/v1/refs/" << StructuredNamespace;
	FCbWriter RequestWriter;
	RequestWriter.BeginObject();
	RequestWriter.BeginArray("ops"_ASV);
	uint32 OpIndex = 0;
	for (const ValueRefType& ValueRef : ValueRefs)
	{
		RequestWriter.BeginObject();
		RequestWriter.AddInteger("opId"_ASV, OpIndex);
		RequestWriter.AddString("op"_ASV, "GET"_ASV);
		FCacheKey Key = ValueRefKeyGetter(ValueRef);
		FString Bucket(Key.Bucket.ToString());
		Bucket.ToLowerInline();
		RequestWriter.AddString("bucket"_ASV, Bucket);
		RequestWriter.AddString("key"_ASV, LexToString(Key.Hash));
		RequestWriter.AddBool("resolveAttachments"_ASV, true);
		RequestWriter.EndObject();
		++OpIndex;
	}
	RequestWriter.EndArray();
	RequestWriter.EndObject();
	FCbFieldIterator RequestFields = RequestWriter.Save();

	TConstArrayView<uint8> BodyBuffer = MakeConstArrayView(RequestFields.GetOuterBuffer());

	int64 ResponseCode = 0;
	for (uint32 Attempts = 0; (Attempts < UE_HTTPDDC_MAX_ATTEMPTS) && !ShouldAbortForShutdown() && (Attempts == 0 || ShouldRetryOnError(ResponseCode)); ++Attempts)
	{
		if (Attempts > 0)
		{
			Request->Reset();
		}

		Request->SetHeader(TEXT("Accept"), TEXT("application/x-ue-cb"));
		Request->SetHeader(TEXT("Content-Type"), TEXT("application/x-ue-cb"));
		const FHttpRequest::Result Result = Request->PerformBlockingUpload<FHttpRequest::Post>(*RefsUri, BodyBuffer);
		ResponseCode = Request->GetResponseCode();

		if (FHttpRequest::IsSuccessResponse(ResponseCode))
		{
			FMemoryView ResponseView = MakeMemoryView(Request->GetResponseBuffer().GetData(), Request->GetResponseBuffer().Num());
			if (ValidateCompactBinary(ResponseView, ECbValidateMode::Default) != ECbValidateError::None)
			{
				UE_LOG(LogDerivedDataCache, Log,
					TEXT("%s: Cache exists returned invalid results."),
					*GetName());
				TArray<FValue> RetVal;
				RetVal.AddDefaulted(ValueRefs.Num());
				return RetVal;
			}

			const FCbObjectView ResponseObject = FCbObjectView(Request->GetResponseBuffer().GetData());

			FCbArrayView ResultsArrayView = ResponseObject["results"_ASV].AsArrayView();

			if (ResultsArrayView.Num() != ValueRefs.Num())
			{
				UE_LOG(LogDerivedDataCache, Log,
					TEXT("%s: Cache exists returned unexpected quantity of results (expected %d, got %d)."),
					*GetName(), ValueRefs.Num(), ResultsArrayView.Num());
				TArray<FValue> RetVal;
				RetVal.AddDefaulted(ValueRefs.Num());
				return RetVal;
			}
			TArray<FValue> RetVal;
			RetVal.AddDefaulted(ValueRefs.Num());
			for (FCbFieldView ResultFieldView : ResultsArrayView)
			{
				FCbObjectView ResultObjectView = ResultFieldView.AsObjectView();
				uint32 OpId = ResultObjectView["opId"_ASV].AsUInt32();
				FCbObjectView ResponseObjectView = ResultObjectView["response"_ASV].AsObjectView();
				int32 StatusCode = ResultObjectView["statusCode"_ASV].AsInt32();

				if (OpId >= (uint32)RetVal.Num())
				{
					FValueDebugContext DebugContext = ValueRefDebugContextGetter(ValueRefs[OpId]);
					UE_LOG(LogDerivedDataCache, Display, TEXT("%s: Cache miss with invalid op index %u for %s from '%.*s'"),
						*GetName(), OpId, *WriteToString<96>(DebugContext.Key), DebugContext.Name.Len(), DebugContext.Name.GetData());
					continue;
				}

				if (!FHttpRequest::IsSuccessResponse(StatusCode))
				{
					FValueDebugContext DebugContext = ValueRefDebugContextGetter(ValueRefs[OpId]);
					UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s: Cache miss with unsuccessful response code %d for %s from '%.*s'"),
						*GetName(), StatusCode, *WriteToString<96>(DebugContext.Key), DebugContext.Name.Len(), DebugContext.Name.GetData());
					continue;
				}

				const FIoHash RawHash = ResponseObjectView["RawHash"_ASV].AsHash();
				const uint64 RawSize = ResponseObjectView["RawSize"_ASV].AsUInt64(MAX_uint64);
				if (RawHash.IsZero() || RawSize == MAX_uint64)
				{
					FValueDebugContext DebugContext = ValueRefDebugContextGetter(ValueRefs[OpId]);
					UE_LOG(LogDerivedDataCache, Display, TEXT("%s: Cache miss with invalid value for %s from '%.*s'"),
						*GetName(), *WriteToString<96>(DebugContext.Key), DebugContext.Name.Len(), DebugContext.Name.GetData());
					continue;
				}

				RetVal[OpId] = FValue(RawHash, RawSize);
			}
			return RetVal;
		}
	}

	TArray<FValue> RetVal;
	RetVal.AddDefaulted(ValueRefs.Num());
	return RetVal;
}

bool FHttpCacheStore::CachedDataProbablyExists(const TCHAR* CacheKey)
{
	TRACE_CPUPROFILER_EVENT_SCOPE(HttpDDC_Exist);
	TRACE_COUNTER_ADD(HttpDDC_Exist, int64(1));
	COOK_STAT(auto Timer = UsageStats.TimeProbablyExists());

	if (ShouldSimulateMiss(CacheKey))
	{
		return false;
	}

#if WITH_DATAREQUEST_HELPER
	// Retry request until we get an accepted response or exhaust allowed number of attempts.
	for (int32 Attempts = 0; Attempts < UE_HTTPDDC_MAX_ATTEMPTS; ++Attempts)
	{
		FDataRequestHelper RequestHelper(GetRequestPools[IsInGameThread()].Get(), *Namespace, *DefaultBucket, CacheKey, nullptr);
		const int64 ResponseCode = RequestHelper.GetResponseCode();

		if (FHttpRequest::IsSuccessResponse(ResponseCode) && RequestHelper.IsSuccess())
		{
			COOK_STAT(Timer.AddHit(0));
			return true;
		}

		if (!ShouldRetryOnError(ResponseCode))
		{
			return false;
		}
	}
#else
	FString Uri = FString::Printf(TEXT("api/v1/c/ddc/%s/%s/%s"), *Namespace, *DefaultBucket, CacheKey);

	// Retry request until we get an accepted response or exhaust allowed number of attempts.
	for (int32 Attempts = 0; Attempts < UE_HTTPDDC_MAX_ATTEMPTS; ++Attempts)
	{
		FScopedRequestPtr Request(GetRequestPools[IsInGameThread()].Get());
		const FHttpRequest::Result Result = Request->PerformBlockingQuery<FHttpRequest::Head>(*Uri);
		const int64 ResponseCode = Request->GetResponseCode();

		if (FHttpRequest::IsSuccessResponse(ResponseCode) || ResponseCode == 400)
		{
			const bool bIsHit = (Result == FHttpRequest::Success && FHttpRequest::IsSuccessResponse(ResponseCode));
			if (bIsHit)
			{
				TRACE_COUNTER_ADD(HttpDDC_ExistHit, int64(1));
				COOK_STAT(Timer.AddHit(0));
			}
			return bIsHit;
		}

		if (!ShouldRetryOnError(ResponseCode))
		{
			break;
		}
	}
#endif

	return false;
}

TBitArray<> FHttpCacheStore::CachedDataProbablyExistsBatch(TConstArrayView<FString> CacheKeys)
{
	TRACE_CPUPROFILER_EVENT_SCOPE(HttpDDC_Exist);
	TRACE_COUNTER_ADD(HttpDDC_Exist, int64(1));
	COOK_STAT(auto Timer = UsageStats.TimeProbablyExists());
#if WITH_DATAREQUEST_HELPER
	for (int32 Attempts = 0; Attempts < UE_HTTPDDC_MAX_ATTEMPTS; ++Attempts)
	{
		FDataRequestHelper RequestHelper(GetRequestPools[IsInGameThread()].Get(), *Namespace, *DefaultBucket, CacheKeys);
		const int64 ResponseCode = RequestHelper.GetResponseCode();

		if (FHttpRequest::IsSuccessResponse(ResponseCode) && RequestHelper.IsSuccess())
		{
			COOK_STAT(Timer.AddHit(0));
			TBitArray<> Results = RequestHelper.IsBatchSuccess();
			int32 ResultIndex = 0;
			for (const FString& CacheKey : CacheKeys)
			{
				if (ShouldSimulateMiss(*CacheKey))
				{
					Results[ResultIndex] = false;
				}
				ResultIndex++;
			}

			return Results;
		}

		if (!ShouldRetryOnError(ResponseCode))
		{
			TBitArray<> Results = RequestHelper.IsBatchSuccess();
			int32 ResultIndex = 0;
			for (const FString& CacheKey : CacheKeys)
			{
				if (ShouldSimulateMiss(*CacheKey))
				{
					Results[ResultIndex] = false;
				}
				ResultIndex++;
			}

			return Results;
		}
	}
#else
	const TCHAR* const Uri = TEXT("api/v1/c/ddc-rpc");

	TAnsiStringBuilder<512> Body;
	const FTCHARToUTF8 AnsiNamespace(*Namespace);
	const FTCHARToUTF8 AnsiBucket(*DefaultBucket);
	Body << "{\"Operations\":[";
	for (const FString& CacheKey : CacheKeys)
	{
		Body << "{\"Namespace\":\"" << AnsiNamespace.Get() << "\",\"Bucket\":\"" << AnsiBucket.Get() << "\",";
		Body << "\"Id\":\"" << FTCHARToUTF8(*CacheKey).Get() << "\",\"Op\":\"HEAD\"},";
	}
	Body.RemoveSuffix(1);
	Body << "]}";

	TConstArrayView<uint8> BodyView(reinterpret_cast<const uint8*>(Body.ToString()), Body.Len());

	// Retry request until we get an accepted response or exhaust allowed number of attempts.
	for (int32 Attempts = 0; Attempts < UE_HTTPDDC_MAX_ATTEMPTS; ++Attempts)
	{
		FScopedRequestPtr Request(GetRequestPools[IsInGameThread()].Get());
		const FHttpRequest::Result Result = Request->PerformBlockingUpload<FHttpRequest::PostJson>(Uri, BodyView);
		const int64 ResponseCode = Request->GetResponseCode();

		if (Result == FHttpRequest::Success && ResponseCode == 200)
		{
			TArray<TSharedPtr<FJsonValue>> ResponseArray = Request->GetResponseAsJsonArray();

			TBitArray<> Exists;
			Exists.Reserve(CacheKeys.Num());
			for (const FString& CacheKey : CacheKeys)
			{
				if (ShouldSimulateMiss(*CacheKey))
				{
					Exists.Add(false);
				}
				else
				{
					const TSharedPtr<FJsonValue>* FoundResponse = Algo::FindByPredicate(ResponseArray, [&CacheKey](const TSharedPtr<FJsonValue>& Response) {
						FString Key;
						Response->TryGetString(Key);
						return Key == CacheKey;
					});

					Exists.Add(FoundResponse != nullptr);
				}
			}

			if (Exists.CountSetBits() == CacheKeys.Num())
			{
				TRACE_COUNTER_ADD(HttpDDC_ExistHit, int64(1));
				COOK_STAT(Timer.AddHit(0));
			}
			return Exists;
		}

		if (!ShouldRetryOnError(ResponseCode))
		{
			break;
		}
	}
#endif

	return TBitArray<>(false, CacheKeys.Num());
}

bool FHttpCacheStore::GetCachedData(const TCHAR* CacheKey, TArray<uint8>& OutData)
{
	TRACE_CPUPROFILER_EVENT_SCOPE(HttpDDC_Get);
	TRACE_COUNTER_ADD(HttpDDC_Get, int64(1));
	COOK_STAT(auto Timer = UsageStats.TimeGet());

	if (ShouldSimulateMiss(CacheKey))
	{
		return false;
	}

#if WITH_DATAREQUEST_HELPER
	// Retry request until we get an accepted response or exhaust allowed number of attempts.
	for (int32 Attempts = 0; Attempts < UE_HTTPDDC_MAX_ATTEMPTS; ++Attempts)
	{
		FDataRequestHelper RequestHelper(GetRequestPools[IsInGameThread()].Get(), *Namespace, *DefaultBucket, CacheKey, &OutData);
		const int64 ResponseCode = RequestHelper.GetResponseCode();

		if (FHttpRequest::IsSuccessResponse(ResponseCode) && RequestHelper.IsSuccess())
		{
			COOK_STAT(Timer.AddHit(OutData.Num()));
			check(OutData.Num() > 0);
			return true;
		}

		if (!ShouldRetryOnError(ResponseCode))
		{
			return false;
		}
	}
#else 
	FString Uri = FString::Printf(TEXT("api/v1/c/ddc/%s/%s/%s.raw"), *Namespace, *DefaultBucket, CacheKey);

	// Retry request until we get an accepted response or exhaust allowed number of attempts.
	for (int32 Attempts = 0; Attempts < UE_HTTPDDC_MAX_ATTEMPTS; ++Attempts)
	{
		FScopedRequestPtr Request(GetRequestPools[IsInGameThread()].Get());
		if (Request.IsValid())
		{
			FHttpRequest::Result Result = Request->PerformBlockingDownload(*Uri, &OutData);
			const uint64 ResponseCode = Request->GetResponseCode();

			// Request was successful, make sure we got all the expected data.
			if (FHttpRequest::IsSuccessResponse(ResponseCode) && VerifyRequest(Request.Get(), *Namespace, *DefaultBucket, CacheKey, OutData))
			{
				TRACE_COUNTER_ADD(HttpDDC_GetHit, int64(1));
				TRACE_COUNTER_ADD(HttpDDC_BytesReceived, int64(Request->GetBytesReceived()));
				COOK_STAT(Timer.AddHit(Request->GetBytesReceived()));
				return true;
			}

			if (!ShouldRetryOnError(ResponseCode))
			{
				return false;
			}
		}
	}
#endif

	return false;
}

FDerivedDataBackendInterface::EPutStatus FHttpCacheStore::PutCachedData(const TCHAR* CacheKey, TArrayView<const uint8> InData, bool bPutEvenIfExists)
{
	TRACE_CPUPROFILER_EVENT_SCOPE(HttpDDC_Put);

	if (!IsWritable())
	{
		UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s is read only. Skipping put of %s"), *GetName(), CacheKey);
		return EPutStatus::NotCached;
	}

	// don't put anything we pretended didn't exist
	if (ShouldSimulateMiss(CacheKey))
	{
		return EPutStatus::Skipped;
	}

#if 0 // No longer WITH_DATAREQUEST_HELPER as async puts are unsupported except through the AsyncPutWrapper which expects the inner backend to perform the put synchronously
	for (int32 Attempts = 0; Attempts < UE_HTTPDDC_MAX_ATTEMPTS; ++Attempts)
	{
		FDataUploadHelper Request(PutRequestPools[IsInGameThread()].Get(), *Namespace, *DefaultBucket,	CacheKey, InData, UsageStats);

		if (ShouldAbortForShutdown())
		{
			return EPutStatus::NotCached;
		}

		const int64 ResponseCode = Request.GetResponseCode();

		if (Request.IsSuccess() && (Request.IsQueued() || FHttpRequest::IsSuccessResponse(ResponseCode)))
		{
			return Request.IsQueued() ? EPutStatus::Executing : EPutStatus::Cached;
		}

		if (!ShouldRetryOnError(ResponseCode))
		{
			return EPutStatus::NotCached;
		}
	}
#else
	COOK_STAT(auto Timer = UsageStats.TimePut());

	FString Uri = FString::Printf(TEXT("api/v1/c/ddc/%s/%s/%s"), *Namespace, *DefaultBucket, CacheKey);
	int64 ResponseCode = 0; uint32 Attempts = 0;

	// Retry request until we get an accepted response or exhaust allowed number of attempts.
	while (ResponseCode == 0 && ++Attempts < UE_HTTPDDC_MAX_ATTEMPTS)
	{
		if (ShouldAbortForShutdown())
		{
			return EPutStatus::NotCached;
		}

		FScopedRequestPtr Request(PutRequestPools[IsInGameThread()].Get());
		if (Request.IsValid())
		{
			// Append the content hash to the header
			HashPayload(Request.Get(), InData);

			Request->PerformBlockingUpload<FHttpRequest::Put>(*Uri, InData);
			ResponseCode = Request->GetResponseCode();

			if (FHttpRequest::IsSuccessResponse(ResponseCode))
			{
				TRACE_COUNTER_ADD(HttpDDC_BytesSent, int64(Request->GetBytesSent()));
				COOK_STAT(Timer.AddHit(Request->GetBytesSent()));
				return EPutStatus::Cached;
			}

			if (!ShouldRetryOnError(ResponseCode))
			{
				return EPutStatus::NotCached;
			}

			ResponseCode = 0;
		}
	}
#endif // WITH_DATAREQUEST_HELPER

	return EPutStatus::NotCached;
}

void FHttpCacheStore::RemoveCachedData(const TCHAR* CacheKey, bool bTransient)
{
	// do not remove transient data as Jupiter does its own verification of the content and cleans itself up
	if (!IsWritable() || bTransient)
		return;
	
	TRACE_CPUPROFILER_EVENT_SCOPE(HttpDDC_Remove);
	FString Uri = FString::Printf(TEXT("api/v1/c/ddc/%s/%s/%s"), *Namespace, *DefaultBucket, CacheKey);
	int64 ResponseCode = 0; uint32 Attempts = 0;

	// Retry request until we get an accepted response or exhaust allowed number of attempts.
	while (ResponseCode == 0 && ++Attempts < UE_HTTPDDC_MAX_ATTEMPTS)
	{
		FScopedRequestPtr Request(PutRequestPools[IsInGameThread()].Get());
		if (Request.IsValid())
		{
			FHttpRequest::Result Result = Request->PerformBlockingQuery<FHttpRequest::Delete>(*Uri, {});
			ResponseCode = Request->GetResponseCode();

			if (ResponseCode == 200)
			{
				return;
			}

			if (!ShouldRetryOnError(ResponseCode))
			{
				return;
			}

			ResponseCode = 0;
		}
	}
}

TSharedRef<FDerivedDataCacheStatsNode> FHttpCacheStore::GatherUsageStats() const
{
	TSharedRef<FDerivedDataCacheStatsNode> Usage =
		MakeShared<FDerivedDataCacheStatsNode>(TEXT("Horde Storage"), FString::Printf(TEXT("%s (%s)"), *Domain, *Namespace), /*bIsLocal*/ false);
	Usage->Stats.Add(TEXT(""), UsageStats);
	return Usage;
}

void FHttpCacheStore::Put(
	const TConstArrayView<FCachePutRequest> Requests,
	IRequestOwner& Owner,
	FOnCachePutComplete&& OnComplete)
{
	for (const FCachePutRequest& Request : Requests)
	{
		const FCacheRecord& Record = Request.Record;
		COOK_STAT(auto Timer = UsageStats.TimePut());
		uint64 BytesSent = 0;
		if (PutCacheRecord(Request.Name, Record, Request.Policy, BytesSent))
		{
			UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s: Cache put complete for %s from '%s'"),
				*GetName(), *WriteToString<96>(Record.GetKey()), *Request.Name);
			TRACE_COUNTER_ADD(HttpDDC_BytesSent, int64(BytesSent));
			COOK_STAT(Timer.AddHit(BytesSent));
			OnComplete(Request.MakeResponse(EStatus::Ok));
		}
		else
		{
			OnComplete(Request.MakeResponse(EStatus::Error));
		}
	}
}

void FHttpCacheStore::Get(
	const TConstArrayView<FCacheGetRequest> Requests,
	IRequestOwner& Owner,
	FOnCacheGetComplete&& OnComplete)
{
	for (const FCacheGetRequest& Request : Requests)
	{
		COOK_STAT(auto Timer = UsageStats.TimeGet());
		EStatus Status = EStatus::Ok;
		if (FOptionalCacheRecord Record = GetCacheRecord(Request.Name, Request.Key, Request.Policy, Status))
		{
			UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s: Cache hit for %s from '%s'"),
				*GetName(), *WriteToString<96>(Request.Key), *Request.Name);
			TRACE_COUNTER_ADD(HttpDDC_BytesReceived, Private::GetCacheRecordCompressedSize(Record.Get()));
			COOK_STAT(Timer.AddHit(Private::GetCacheRecordCompressedSize(Record.Get())));
			OnComplete({Request.Name, MoveTemp(Record).Get(), Request.UserData, Status});
		}
		else
		{
			OnComplete(Request.MakeResponse(Status));
		}
	}
}

void FHttpCacheStore::PutValue(
	const TConstArrayView<FCachePutValueRequest> Requests,
	IRequestOwner& Owner,
	FOnCachePutValueComplete&& OnComplete)
{
	for (const FCachePutValueRequest& Request : Requests)
	{
		COOK_STAT(auto Timer = UsageStats.TimePut());
		uint64 WriteSize = 0;
		if (PutCacheValue(Request.Name, Request.Key, Request.Value, Request.Policy, WriteSize))
		{
			UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s: Cache put complete for %s from '%s'"),
				*GetName(), *WriteToString<96>(Request.Key), *Request.Name);
			TRACE_COUNTER_ADD(HttpDDC_BytesSent, WriteSize);
			COOK_STAT(if (WriteSize) { Timer.AddHit(WriteSize); });
			OnComplete(Request.MakeResponse(EStatus::Ok));
		}
		else
		{
			OnComplete(Request.MakeResponse(EStatus::Error));
		}
	}
}

void FHttpCacheStore::GetValue(
	const TConstArrayView<FCacheGetValueRequest> Requests,
	IRequestOwner& Owner,
	FOnCacheGetValueComplete&& OnComplete)
{
	COOK_STAT(double StartTime = FPlatformTime::Seconds());
	COOK_STAT(bool bIsInGameThread = IsInGameThread());

	FScopedRequestPtr HttpRequest(GetRequestPools[IsInGameThread()].Get());
	int64 HitBytes = 0;

	bool bBatchExistsCandidate = true;
	for (const FCacheGetValueRequest& Request : Requests)
	{
		if (!EnumHasAnyFlags(Request.Policy, ECachePolicy::SkipData))
		{
			bBatchExistsCandidate = false;
			break;
		}
	}

	if (bBatchExistsCandidate)
	{
		auto KeyGetter = [](const FCacheGetValueRequest& Request)
		{
			return Request.Key;
		};

		auto DebugContextGetter = [](const FCacheGetValueRequest& Request)
		{
			return FValueDebugContext{ Request.Name, Request.Key, FString(TEXT("Default")) };
		};

		TArray<FValue> Values = RefCachedDataProbablyExistsBatch<FCacheGetValueRequest>(Requests, KeyGetter, DebugContextGetter, HttpRequest.Get());

		for (int32 RequestIndex = 0; RequestIndex < Requests.Num(); ++RequestIndex)
		{
			const FCacheGetValueRequest& Request = Requests[RequestIndex];
			if (Values[RequestIndex] == FValue::Null)
			{
				COOK_STAT(UsageStats.GetStats.Accumulate(FCookStats::CallStats::EHitOrMiss::Miss, FCookStats::CallStats::EStatType::Counter, 1l, bIsInGameThread));
				OnComplete(Request.MakeResponse(EStatus::Error));
			}
			else
			{
				UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s: Cache hit for %s from '%s'"),
					*GetName(), *WriteToString<96>(Request.Key), *Request.Name);
				COOK_STAT(UsageStats.GetStats.Accumulate(FCookStats::CallStats::EHitOrMiss::Hit, FCookStats::CallStats::EStatType::Counter, 1l, bIsInGameThread));
				OnComplete({ Request.Name, Request.Key, Values[RequestIndex], Request.UserData, EStatus::Ok });
			}
		}
	}
	else
	{
		for (const FCacheGetValueRequest& Request : Requests)
		{
			FValue Value;
			if (!GetCacheValue(Request.Name, Request.Key, Request.Policy, Value, HttpRequest.Get()))
			{
				COOK_STAT(UsageStats.GetStats.Accumulate(FCookStats::CallStats::EHitOrMiss::Miss, FCookStats::CallStats::EStatType::Counter, 1l, bIsInGameThread));
				OnComplete(Request.MakeResponse(EStatus::Error));
			}
			else
			{
				if (!IsValueDataReady(Value, Request.Policy) && !EnumHasAnyFlags(Request.Policy, ECachePolicy::SkipData))
				{
					// With inline fetching, expect we will always have a value we can use.  Even SkipData/Exists can rely on the blob existing if the ref is reported to exist.
					UE_LOG(LogDerivedDataCache, Log, TEXT("%s: Cache miss due to inlining failure for %s from '%s'"),
						*GetName(), *WriteToString<96>(Request.Key), *Request.Name);
					COOK_STAT(UsageStats.GetStats.Accumulate(FCookStats::CallStats::EHitOrMiss::Miss, FCookStats::CallStats::EStatType::Counter, 1l, bIsInGameThread));
					OnComplete(Request.MakeResponse(EStatus::Error));
				}
				else
				{
					UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s: Cache hit for %s from '%s'"),
						*GetName(), *WriteToString<96>(Request.Key), *Request.Name);
					uint64 ValueSize = Value.GetData().GetCompressedSize();
					TRACE_COUNTER_ADD(HttpDDC_BytesReceived, ValueSize);
					HitBytes += ValueSize;
					COOK_STAT(UsageStats.GetStats.Accumulate(FCookStats::CallStats::EHitOrMiss::Hit, FCookStats::CallStats::EStatType::Counter, 1l, bIsInGameThread));
					OnComplete({ Request.Name, Request.Key, Value, Request.UserData, EStatus::Ok });
				}
			}
		}
	}

	COOK_STAT(const int64 CyclesUsed = int64((FPlatformTime::Seconds() - StartTime) / FPlatformTime::GetSecondsPerCycle()));
	COOK_STAT(UsageStats.GetStats.Accumulate(FCookStats::CallStats::EHitOrMiss::Hit, FCookStats::CallStats::EStatType::Cycles, CyclesUsed, bIsInGameThread));
	COOK_STAT(UsageStats.GetStats.Accumulate(FCookStats::CallStats::EHitOrMiss::Hit, FCookStats::CallStats::EStatType::Bytes, HitBytes, bIsInGameThread));
}

void FHttpCacheStore::GetChunks(
	const TConstArrayView<FCacheGetChunkRequest> Requests,
	IRequestOwner& Owner,
	FOnCacheGetChunkComplete&& OnComplete)
{
	// TODO: This is inefficient because Jupiter doesn't allow us to get only part of a compressed blob, so we have to
	//		 get the whole thing and then decompress only the portion we need.  Furthermore, because there is no propagation
	//		 between cache stores during chunk requests, the fetched result won't end up in the local store.
	//		 These efficiency issues will be addressed by changes to the Hierarchy that translate chunk requests that
	//		 are missing in local/fast stores and have to be retrieved from slow stores into record requests instead.  That
	//		 will make this code path unused/uncommon as Jupiter will most always be a slow store with a local/fast store in front of it.
	//		 Regardless, to adhere to the functional contract, this implementation must exist.
	TArray<FCacheGetChunkRequest, TInlineAllocator<16>> SortedRequests(Requests);
	SortedRequests.StableSort(TChunkLess());

	bool bHasValue = false;
	FValue Value;
	FValueId ValueId;
	FCacheKey ValueKey;
	FCompressedBuffer ValueBuffer;
	FCompressedBufferReader ValueReader;
	EStatus ValueStatus = EStatus::Error;
	FOptionalCacheRecord Record;
	for (const FCacheGetChunkRequest& Request : SortedRequests)
	{
		const bool bExistsOnly = EnumHasAnyFlags(Request.Policy, ECachePolicy::SkipData);
		COOK_STAT(auto Timer = bExistsOnly ? UsageStats.TimeProbablyExists() : UsageStats.TimeGet());
		if (!(bHasValue && ValueKey == Request.Key && ValueId == Request.Id) || ValueReader.HasSource() < !bExistsOnly)
		{
			ValueStatus = EStatus::Error;
			ValueReader.ResetSource();
			ValueKey = {};
			ValueId.Reset();
			Value.Reset();
			bHasValue = false;
			if (Request.Id.IsValid())
			{
				if (!(Record && Record.Get().GetKey() == Request.Key))
				{
					FCacheRecordPolicyBuilder PolicyBuilder(ECachePolicy::None);
					PolicyBuilder.AddValuePolicy(Request.Id, Request.Policy);
					Record.Reset();
					Record = GetCacheRecordOnly(Request.Name, Request.Key, PolicyBuilder.Build());
				}
				if (Record)
				{
					const FValueWithId& ValueWithId = Record.Get().GetValue(Request.Id);
					bHasValue = ValueWithId.IsValid();
					Value = ValueWithId;
					ValueId = Request.Id;
					ValueKey = Request.Key;

					if (IsValueDataReady(Value, Request.Policy))
					{
						ValueReader.SetSource(Value.GetData());
					}
					else
					{
						auto HashGetter = [](const FValueWithId& Value)
						{
							return Value.GetRawHash();
						};

						auto DebugContextGetter = [&Request](const FValueWithId& Value)
						{
							return FValueDebugContext{ Request.Name, Request.Key, FString(*WriteToString<16>(Value.GetId())) };
						};

						TArray<FCompressedBuffer> ValueBuffers;
						if (TryGetCachedDataBatch<FValueWithId>(::MakeArrayView({ ValueWithId }), ValueBuffers, HashGetter, DebugContextGetter).CountSetBits() == 1)
						{
							ValueBuffer = ValueBuffers[0];
							ValueReader.SetSource(ValueBuffer);
						}
						else
						{
							ValueBuffer.Reset();
							ValueReader.ResetSource();
						}
					}
				}
			}
			else
			{
				ValueKey = Request.Key;
				bHasValue = GetCacheValue(Request.Name, Request.Key, Request.Policy, Value);
				if (IsValueDataReady(Value, Request.Policy))
				{
					ValueReader.SetSource(Value.GetData());
				}
				else
				{
					auto HashGetter = [](const FValue& Value)
					{
						return Value.GetRawHash();
					};

					auto DebugContextGetter = [&Request](const FValue& Value)
					{
						return FValueDebugContext{ Request.Name, Request.Key, FString(TEXT("Default")) };
					};

					TArray<FCompressedBuffer> ValueBuffers;
					if (TryGetCachedDataBatch<FValue>({ Value }, ValueBuffers, HashGetter, DebugContextGetter).CountSetBits() == 1)
					{
						ValueBuffer = ValueBuffers[0];
						ValueReader.SetSource(ValueBuffer);
					}
					else
					{
						ValueBuffer.Reset();
						ValueReader.ResetSource();
					}
				}
			}
		}
		if (bHasValue)
		{
			const uint64 RawOffset = FMath::Min(Value.GetRawSize(), Request.RawOffset);
			const uint64 RawSize = FMath::Min(Value.GetRawSize() - RawOffset, Request.RawSize);
			UE_LOG(LogDerivedDataCache, Verbose, TEXT("%s: Cache hit for %s from '%s'"),
				*GetName(), *WriteToString<96>(Request.Key, '/', Request.Id), *Request.Name);
			COOK_STAT(Timer.AddHit(!bExistsOnly ? RawSize : 0));
			FSharedBuffer Buffer;
			if (!bExistsOnly)
			{
				Buffer = ValueReader.Decompress(RawOffset, RawSize);
			}
			const EStatus ChunkStatus = bExistsOnly || Buffer.GetSize() == RawSize ? EStatus::Ok : EStatus::Error;
			OnComplete({Request.Name, Request.Key, Request.Id, Request.RawOffset,
				RawSize, Value.GetRawHash(), MoveTemp(Buffer), Request.UserData, ChunkStatus});
			continue;
		}

		OnComplete(Request.MakeResponse(EStatus::Error));
	}
}

} // UE::DerivedData

#endif // WITH_HTTP_DDC_BACKEND

namespace UE::DerivedData
{

ILegacyCacheStore* CreateHttpCacheStore(
	const TCHAR* NodeName,
	const TCHAR* ServiceUrl,
	bool bResolveHostCanonicalName,
	const TCHAR* Namespace,
	const TCHAR* StructuredNamespace,
	const TCHAR* OAuthProvider,
	const TCHAR* OAuthClientId,
	const TCHAR* OAuthData,
	const TCHAR* OAuthScope,
	const FDerivedDataBackendInterface::ESpeedClass* ForceSpeedClass,
	EBackendLegacyMode LegacyMode,
	bool bReadOnly)
{
#if WITH_HTTP_DDC_BACKEND
	FHttpCacheStore* Backend = new FHttpCacheStore(ServiceUrl, bResolveHostCanonicalName, Namespace, StructuredNamespace, OAuthProvider, OAuthClientId, OAuthData, OAuthScope, LegacyMode, bReadOnly);
	if (Backend->IsUsable())
	{
		return Backend;
	}
	UE_LOG(LogDerivedDataCache, Warning, TEXT("Node %s could not contact the service (%s), will not use it"), NodeName, ServiceUrl);
	delete Backend;
	return nullptr;
#else
	UE_LOG(LogDerivedDataCache, Warning, TEXT("HTTP backend is not yet supported in the current build configuration."));
	return nullptr;
#endif
}

FDerivedDataBackendInterface* GetAnyHttpCacheStore(
	FString& OutDomain,
	FString& OutOAuthProvider,
	FString& OutOAuthClientId,
	FString& OutOAuthSecret,
	FString& OutOAuthScope,
	FString& OutNamespace,
	FString& OutStructuredNamespace)
{
#if WITH_HTTP_DDC_BACKEND
	if (FHttpCacheStore* HttpBackend = FHttpCacheStore::GetAny())
	{
		OutDomain = HttpBackend->GetDomain();
		OutOAuthProvider = HttpBackend->GetOAuthProvider();
		OutOAuthClientId = HttpBackend->GetOAuthClientId();
		OutOAuthSecret = HttpBackend->GetOAuthSecret();
		OutOAuthScope = HttpBackend->GetOAuthScope();
		OutNamespace = HttpBackend->GetNamespace();
		OutStructuredNamespace = HttpBackend->GetStructuredNamespace();

		return HttpBackend;
	}
	return nullptr;
#else
	return nullptr;
#endif
}

} // UE::DerivedData