// Copyright 1998-2014 Epic Games, Inc. All Rights Reserved.

#include "DirectoryWatcherPrivatePCH.h"

FDirectoryWatcherWindows::FDirectoryWatcherWindows()
{
	NumRequests = 0;
}

FDirectoryWatcherWindows::~FDirectoryWatcherWindows()
{
	if ( RequestMap.Num() != 0 )
	{
		// Delete any remaining requests here. These requests are likely from modules which are still loaded at the time that this module unloads.
		for (TMap<FString, FDirectoryWatchRequestWindows*>::TConstIterator RequestIt(RequestMap); RequestIt; ++RequestIt)
		{
			if ( ensure(RequestIt.Value()) )
			{
				// make sure we end the watch request, as we may get a callback if a request is in flight
				RequestIt.Value()->EndWatchRequest();
				delete RequestIt.Value();
				NumRequests--;
			}
		}

		RequestMap.Empty();
	}

	if ( RequestsPendingDelete.Num() != 0 )
	{
		for ( int32 RequestIdx = 0; RequestIdx < RequestsPendingDelete.Num(); ++RequestIdx )
		{
			delete RequestsPendingDelete[RequestIdx];
			NumRequests--;
		}
	}

	// Make sure every request that was created is destroyed
	ensure(NumRequests == 0);
}

bool FDirectoryWatcherWindows::RegisterDirectoryChangedCallback( const FString& Directory, const FDirectoryChanged& InDelegate )
{
	FDirectoryWatchRequestWindows** RequestPtr = RequestMap.Find(Directory);
	FDirectoryWatchRequestWindows* Request = NULL;
	
	if ( RequestPtr )
	{
		// There should be no NULL entries in the map
		check (*RequestPtr);

		Request = *RequestPtr;
	}
	else
	{
		Request = new FDirectoryWatchRequestWindows();
		NumRequests++;

		// Begin reading directory changes
		if ( !Request->Init(Directory) )
		{
			uint32 Error = GetLastError();
			UE_LOG(LogDirectoryWatcher, Warning, TEXT("Failed to begin reading directory changes for %s. Error: %d"), *Directory, Error);
			delete Request;
			NumRequests--;
			return false;
		}

		RequestMap.Add(Directory, Request);
	}

	Request->AddDelegate(InDelegate);

	return true;
}

bool FDirectoryWatcherWindows::UnregisterDirectoryChangedCallback( const FString& Directory, const FDirectoryChanged& InDelegate )
{
	FDirectoryWatchRequestWindows** RequestPtr = RequestMap.Find(Directory);
	
	if ( RequestPtr )
	{
		// There should be no NULL entries in the map
		check (*RequestPtr);

		FDirectoryWatchRequestWindows* Request = *RequestPtr;

		if ( Request->RemoveDelegate(InDelegate) )
		{
			if ( !Request->HasDelegates() )
			{
				// Remove from the active map and add to the pending delete list
				RequestMap.Remove(Directory);
				RequestsPendingDelete.AddUnique(Request);

				// Signal to end the watch which will mark this request for deletion
				Request->EndWatchRequest();
			}

			return true;
		}
		
	}

	return false;
}

void FDirectoryWatcherWindows::Tick( float DeltaSeconds )
{
	TArray<HANDLE> DirectoryHandles;
	TMap<FString, FDirectoryWatchRequestWindows*> InvalidRequestsToDelete;

	// Find all handles to listen to and invalid requests to delete
	for (TMap<FString, FDirectoryWatchRequestWindows*>::TConstIterator RequestIt(RequestMap); RequestIt; ++RequestIt)
	{
		if ( RequestIt.Value()->IsPendingDelete() )
		{
			InvalidRequestsToDelete.Add(RequestIt.Key(), RequestIt.Value());
		}
		else
		{
			DirectoryHandles.Add(RequestIt.Value()->GetDirectoryHandle());
		}
	}

	// Remove all invalid requests from the request map and add them to the pending delete list so they will be deleted below
	for (TMap<FString, FDirectoryWatchRequestWindows*>::TConstIterator RequestIt(InvalidRequestsToDelete); RequestIt; ++RequestIt)
	{
		RequestMap.Remove(RequestIt.Key());
		RequestsPendingDelete.AddUnique(RequestIt.Value());
	}

	// Trigger any file changed delegates that are queued up
	if ( DirectoryHandles.Num() > 0 )
	{
		MsgWaitForMultipleObjectsEx(DirectoryHandles.Num(), DirectoryHandles.GetTypedData(), 0, QS_ALLEVENTS, MWMO_ALERTABLE);
	}

	// Delete any stale or invalid requests
	for ( int32 RequestIdx = RequestsPendingDelete.Num() - 1; RequestIdx >= 0; --RequestIdx )
	{
		FDirectoryWatchRequestWindows* Request = RequestsPendingDelete[RequestIdx];

		if ( Request->IsPendingDelete() )
		{
			// This request is safe to delete. Delete and remove it from the list
			delete Request;
			NumRequests--;
			RequestsPendingDelete.RemoveAt(RequestIdx);
		}
	}

	// Finally, trigger any file change notification delegates
	for (TMap<FString, FDirectoryWatchRequestWindows*>::TConstIterator RequestIt(RequestMap); RequestIt; ++RequestIt)
	{
		RequestIt.Value()->ProcessPendingNotifications();
	}
}