/*

 * Copyright (C) 2007, 2008 Apple Inc. All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * 1.  Redistributions of source code must retain the above copyright

 *     notice, this list of conditions and the following disclaimer.

 * 2.  Redistributions in binary form must reproduce the above copyright

 *     notice, this list of conditions and the following disclaimer in the

 *     documentation and/or other materials provided with the distribution.

 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of

 *     its contributors may be used to endorse or promote products derived

 *     from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY

 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY

 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

#include "config.h"

#include "MainThread.h"

#include "CurrentTime.h"

#include "Deque.h"

#include "StdLibExtras.h"

#include "Threading.h"

#if PLATFORM(CHROMIUM)

#error Chromium uses a different main thread implementation

#endif

namespace WTF {

struct FunctionWithContext {

    MainThreadFunction* function;

    void* context;

    ThreadCondition* syncFlag;

    FunctionWithContext(MainThreadFunction* function = 0, void* context = 0, ThreadCondition* syncFlag = 0)

        : function(function)

        , context(context)

        , syncFlag(syncFlag)

    { 

    }

    bool operator == (const FunctionWithContext& o)

    {

        return function == o.function

            && context == o.context

            && syncFlag == o.syncFlag;

    }

};

class FunctionWithContextFinder {

public:

    FunctionWithContextFinder(const FunctionWithContext& m) : m(m) {}

    bool operator() (FunctionWithContext& o) { return o == m; }

    FunctionWithContext m;

};

typedef Deque<FunctionWithContext> FunctionQueue;

static bool callbacksPaused; // This global variable is only accessed from main thread.

#if !PLATFORM(MAC) && !PLATFORM(QT)

static ThreadIdentifier mainThreadIdentifier;

#endif

static Mutex& mainThreadFunctionQueueMutex()

{

    DEFINE_STATIC_LOCAL(Mutex, staticMutex, ());

    return staticMutex;

}

static FunctionQueue& functionQueue()

{

    DEFINE_STATIC_LOCAL(FunctionQueue, staticFunctionQueue, ());

    return staticFunctionQueue;

}

#if !PLATFORM(MAC)

void initializeMainThread()

{

    static bool initializedMainThread;

    if (initializedMainThread)

        return;

    initializedMainThread = true;

#if !PLATFORM(QT)

    mainThreadIdentifier = currentThread();

#endif

    mainThreadFunctionQueueMutex();

    initializeMainThreadPlatform();

}

#else

static pthread_once_t initializeMainThreadKeyOnce = PTHREAD_ONCE_INIT;

static void initializeMainThreadOnce()

{

    mainThreadFunctionQueueMutex();

    initializeMainThreadPlatform();

}

void initializeMainThread()

{

    pthread_once(&initializeMainThreadKeyOnce, initializeMainThreadOnce);

}

static void initializeMainThreadToProcessMainThreadOnce()

{

    mainThreadFunctionQueueMutex();

    initializeMainThreadToProcessMainThreadPlatform();

}

void initializeMainThreadToProcessMainThread()

{

    pthread_once(&initializeMainThreadKeyOnce, initializeMainThreadToProcessMainThreadOnce);

}

#endif

// 0.1 sec delays in UI is approximate threshold when they become noticeable. Have a limit that's half of that.

static const double maxRunLoopSuspensionTime = 0.05;

void dispatchFunctionsFromMainThread()

{

    ASSERT(isMainThread());

    if (callbacksPaused)

        return;

    double startTime = currentTime();

    FunctionWithContext invocation;

    while (true) {

        {

            MutexLocker locker(mainThreadFunctionQueueMutex());

            if (!functionQueue().size())

                break;

            invocation = functionQueue().takeFirst();

        }

        invocation.function(invocation.context);

        if (invocation.syncFlag)

            invocation.syncFlag->signal();

        // If we are running accumulated functions for too long so UI may become unresponsive, we need to

        // yield so the user input can be processed. Otherwise user may not be able to even close the window.

        // This code has effect only in case the scheduleDispatchFunctionsOnMainThread() is implemented in a way that

        // allows input events to be processed before we are back here.

        if (currentTime() - startTime > maxRunLoopSuspensionTime) {

            scheduleDispatchFunctionsOnMainThread();

            break;

        }

    }

}

void callOnMainThread(MainThreadFunction* function, void* context)

{

    ASSERT(function);

    bool needToSchedule = false;

    {

        MutexLocker locker(mainThreadFunctionQueueMutex());

        needToSchedule = functionQueue().size() == 0;

        functionQueue().append(FunctionWithContext(function, context));

    }

    if (needToSchedule)

        scheduleDispatchFunctionsOnMainThread();

}

void callOnMainThreadAndWait(MainThreadFunction* function, void* context)

{

    ASSERT(function);

    if (isMainThread()) {

        function(context);

        return;

    }

    ThreadCondition syncFlag;

    Mutex& functionQueueMutex = mainThreadFunctionQueueMutex();

    MutexLocker locker(functionQueueMutex);

    functionQueue().append(FunctionWithContext(function, context, &syncFlag));

    if (functionQueue().size() == 1)

        scheduleDispatchFunctionsOnMainThread();

    syncFlag.wait(functionQueueMutex);

}

void cancelCallOnMainThread(MainThreadFunction* function, void* context)

{

    ASSERT(function);

    MutexLocker locker(mainThreadFunctionQueueMutex());

    FunctionWithContextFinder pred(FunctionWithContext(function, context));

    while (true) {

        // We must redefine 'i' each pass, because the itererator's operator= 

        // requires 'this' to be valid, and remove() invalidates all iterators

        FunctionQueue::iterator i(functionQueue().findIf(pred));

        if (i == functionQueue().end())

            break;

        functionQueue().remove(i);

    }

}

void setMainThreadCallbacksPaused(bool paused)

{

    ASSERT(isMainThread());

    if (callbacksPaused == paused)

        return;

    callbacksPaused = paused;

    if (!callbacksPaused)

        scheduleDispatchFunctionsOnMainThread();

}

#if !PLATFORM(MAC) && !PLATFORM(QT) && !PLATFORM(BREWMP)

bool isMainThread()

{

    return currentThread() == mainThreadIdentifier;

}

#endif

} // namespace WTF