/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
 * Maintains a circular buffer of recent messages, and notifies
 * listeners when new messages are logged.
 */

/* Threadsafe. */

#include "nsMemory.h"
#include "nsCOMArray.h"
#include "nsThreadUtils.h"

#include "nsConsoleService.h"
#include "nsConsoleMessage.h"
#include "nsIClassInfoImpl.h"
#include "nsIConsoleListener.h"
#include "nsPrintfCString.h"

#include "mozilla/Debug.h"
#include "mozilla/Preferences.h"

using namespace mozilla;

NS_IMPL_ADDREF(nsConsoleService)
NS_IMPL_RELEASE(nsConsoleService)
NS_IMPL_CLASSINFO(nsConsoleService, nullptr, nsIClassInfo::THREADSAFE | nsIClassInfo::SINGLETON, NS_CONSOLESERVICE_CID)
NS_IMPL_QUERY_INTERFACE1_CI(nsConsoleService, nsIConsoleService)
NS_IMPL_CI_INTERFACE_GETTER1(nsConsoleService, nsIConsoleService)

static bool sLoggingEnabled = true;
static bool sLoggingBuffered = true;

nsConsoleService::nsConsoleService()
    : mMessages(nullptr)
    , mCurrent(0)
    , mFull(false)
    , mDeliveringMessage(false)
    , mLock("nsConsoleService.mLock")
{
    // XXX grab this from a pref!
    // hm, but worry about circularity, bc we want to be able to report
    // prefs errs...
    mBufferSize = 250;
}

nsConsoleService::~nsConsoleService()
{
    uint32_t i = 0;
    while (i < mBufferSize && mMessages[i] != nullptr) {
        NS_RELEASE(mMessages[i]);
        i++;
    }

    if (mMessages)
        nsMemory::Free(mMessages);
}

class AddConsolePrefWatchers : public nsRunnable
{
public:
    AddConsolePrefWatchers(nsConsoleService* aConsole) : mConsole(aConsole) {}

    NS_IMETHOD Run()
    {
        Preferences::AddBoolVarCache(&sLoggingEnabled, "consoleservice.enabled", true);
        Preferences::AddBoolVarCache(&sLoggingBuffered, "consoleservice.buffered", true);
        if (!sLoggingBuffered) {
            mConsole->Reset();
        }
        return NS_OK;
    }

private:
    nsRefPtr<nsConsoleService> mConsole;
};

nsresult
nsConsoleService::Init()
{
    mMessages = (nsIConsoleMessage **)
        nsMemory::Alloc(mBufferSize * sizeof(nsIConsoleMessage *));
    if (!mMessages)
        return NS_ERROR_OUT_OF_MEMORY;

    // Array elements should be 0 initially for circular buffer algorithm.
    memset(mMessages, 0, mBufferSize * sizeof(nsIConsoleMessage *));

    NS_DispatchToMainThread(new AddConsolePrefWatchers(this));

    return NS_OK;
}

namespace {

class LogMessageRunnable : public nsRunnable
{
public:
    LogMessageRunnable(nsIConsoleMessage* message, nsConsoleService* service)
        : mMessage(message)
        , mService(service)
    { }

    NS_DECL_NSIRUNNABLE

private:
    nsCOMPtr<nsIConsoleMessage> mMessage;
    nsRefPtr<nsConsoleService> mService;
};

typedef nsCOMArray<nsIConsoleListener> ListenerArrayType;

PLDHashOperator
CollectCurrentListeners(nsISupports* aKey, nsIConsoleListener* aValue,
                        void* closure)
{
    ListenerArrayType* listeners = static_cast<ListenerArrayType*>(closure);
    listeners->AppendObject(aValue);
    return PL_DHASH_NEXT;
}

NS_IMETHODIMP
LogMessageRunnable::Run()
{
    MOZ_ASSERT(NS_IsMainThread());

    // Snapshot of listeners so that we don't reenter this hash during
    // enumeration.
    nsCOMArray<nsIConsoleListener> listeners;
    mService->EnumerateListeners(CollectCurrentListeners, &listeners);

    mService->SetIsDelivering();

    for (int32_t i = 0; i < listeners.Count(); ++i)
        listeners[i]->Observe(mMessage);

    mService->SetDoneDelivering();

    return NS_OK;
}

} // anonymous namespace

// nsIConsoleService methods
NS_IMETHODIMP
nsConsoleService::LogMessage(nsIConsoleMessage *message)
{
    return LogMessageWithMode(message, OutputToLog);
}

nsresult
nsConsoleService::LogMessageWithMode(nsIConsoleMessage *message, nsConsoleService::OutputMode outputMode)
{
    if (message == nullptr)
        return NS_ERROR_INVALID_ARG;

    if (!sLoggingEnabled) {
        return NS_OK;
    }

    if (NS_IsMainThread() && mDeliveringMessage) {
        nsString msg;
        message->GetMessageMoz(getter_Copies(msg));
        NS_WARNING(nsPrintfCString("Reentrancy error: some client attempted "
            "to display a message to the console while in a console listener. "
            "The following message was discarded: \"%s\"",
            NS_ConvertUTF16toUTF8(msg).get()).get());
        return NS_ERROR_FAILURE;
    }

    nsRefPtr<LogMessageRunnable> r;
    nsIConsoleMessage *retiredMessage;

    if (sLoggingBuffered) {
        NS_ADDREF(message); // early, in case it's same as replaced below.
    }

    /*
     * Lock while updating buffer, and while taking snapshot of
     * listeners array.
     */
    {
        MutexAutoLock lock(mLock);

        nsString msg;
        message->GetMessageMoz(getter_Copies(msg));
        LogOptions options = kPrintToDebugger | kPrintNewLine;
        if (outputMode == OutputToLog) {
            options |= kPrintErrorLog;
        }
        PrintToDebugger(msg, nullptr, options);

        /*
         * If there's already a message in the slot we're about to replace,
         * we've wrapped around, and we need to release the old message.  We
         * save a pointer to it, so we can release below outside the lock.
         */
        retiredMessage = mMessages[mCurrent];

        if (sLoggingBuffered) {
            mMessages[mCurrent++] = message;
            if (mCurrent == mBufferSize) {
                mCurrent = 0; // wrap around.
                mFull = true;
            }
        }

        if (mListeners.Count() > 0) {
            r = new LogMessageRunnable(message, this);
        }
    }

    if (retiredMessage != nullptr)
        NS_RELEASE(retiredMessage);

    if (r)
        NS_DispatchToMainThread(r);

    return NS_OK;
}

void
nsConsoleService::EnumerateListeners(ListenerHash::EnumReadFunction aFunction,
                                     void* aClosure)
{
    MutexAutoLock lock(mLock);
    mListeners.EnumerateRead(aFunction, aClosure);
}

NS_IMETHODIMP
nsConsoleService::LogStringMessage(const char16_t *message)
{
    if (!sLoggingEnabled) {
        return NS_OK;
    }

    nsRefPtr<nsConsoleMessage> msg(new nsConsoleMessage(message));
    return this->LogMessage(msg);
}

NS_IMETHODIMP
nsConsoleService::GetMessageArray(uint32_t *count, nsIConsoleMessage ***messages)
{
    nsIConsoleMessage **messageArray;

    /*
     * Lock the whole method, as we don't want anyone mucking with mCurrent or
     * mFull while we're copying out the buffer.
     */
    MutexAutoLock lock(mLock);

    if (mCurrent == 0 && !mFull) {
        /*
         * Make a 1-length output array so that nobody gets confused,
         * and return a count of 0.  This should result in a 0-length
         * array object when called from script.
         */
        messageArray = (nsIConsoleMessage **)
            nsMemory::Alloc(sizeof (nsIConsoleMessage *));
        *messageArray = nullptr;
        *messages = messageArray;
        *count = 0;

        return NS_OK;
    }

    uint32_t resultSize = mFull ? mBufferSize : mCurrent;
    messageArray =
        (nsIConsoleMessage **)nsMemory::Alloc((sizeof (nsIConsoleMessage *))
                                              * resultSize);

    if (messageArray == nullptr) {
        *messages = nullptr;
        *count = 0;
        return NS_ERROR_FAILURE;
    }

    uint32_t i;
    if (mFull) {
        for (i = 0; i < mBufferSize; i++) {
            // if full, fill the buffer starting from mCurrent (which'll be
            // oldest) wrapping around the buffer to the most recent.
            messageArray[i] = mMessages[(mCurrent + i) % mBufferSize];
            NS_ADDREF(messageArray[i]);
        }
    } else {
        for (i = 0; i < mCurrent; i++) {
            messageArray[i] = mMessages[i];
            NS_ADDREF(messageArray[i]);
        }
    }
    *count = resultSize;
    *messages = messageArray;

    return NS_OK;
}

NS_IMETHODIMP
nsConsoleService::RegisterListener(nsIConsoleListener *listener)
{
    if (!NS_IsMainThread()) {
        NS_ERROR("nsConsoleService::RegisterListener is main thread only.");
        return NS_ERROR_NOT_SAME_THREAD;
    }

    nsCOMPtr<nsISupports> canonical = do_QueryInterface(listener);

    MutexAutoLock lock(mLock);
    if (mListeners.GetWeak(canonical)) {
        // Reregistering a listener isn't good
        return NS_ERROR_FAILURE;
    }
    mListeners.Put(canonical, listener);
    return NS_OK;
}

NS_IMETHODIMP
nsConsoleService::UnregisterListener(nsIConsoleListener *listener)
{
    if (!NS_IsMainThread()) {
        NS_ERROR("nsConsoleService::UnregisterListener is main thread only.");
        return NS_ERROR_NOT_SAME_THREAD;
    }

    nsCOMPtr<nsISupports> canonical = do_QueryInterface(listener);

    MutexAutoLock lock(mLock);

    if (!mListeners.GetWeak(canonical)) {
        // Unregistering a listener that was never registered?
        return NS_ERROR_FAILURE;
    }
    mListeners.Remove(canonical);
    return NS_OK;
}

NS_IMETHODIMP
nsConsoleService::Reset()
{
    /*
     * Make sure nobody trips into the buffer while it's being reset
     */
    MutexAutoLock lock(mLock);

    mCurrent = 0;
    mFull = false;

    /*
     * Free all messages stored so far (cf. destructor)
     */
    for (uint32_t i = 0; i < mBufferSize && mMessages[i] != nullptr; i++)
        NS_RELEASE(mMessages[i]);

    return NS_OK;
}