/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* 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/. */

#include "IDecodingTask.h"

#include "gfxPrefs.h"

#include "nsThreadUtils.h"

#include "Decoder.h"

#include "DecodePool.h"

#include "RasterImage.h"

#include "SurfaceCache.h"

#include "mozilla/SystemGroup.h"

namespace mozilla {

using gfx::IntRect;

namespace image {

///////////////////////////////////////////////////////////////////////////////

// Helpers for sending notifications to the image associated with a decoder.

///////////////////////////////////////////////////////////////////////////////

void IDecodingTask::EnsureHasEventTarget(NotNull<RasterImage*> aImage) {

  if (!mEventTarget) {

    // We determine the event target as late as possible, at the first dispatch

    // time, because the observers bound to an imgRequest will affect it.

    // We cache it rather than query for the event target each time because the

    // event target can change. We don't want to risk events being executed in

    // a different order than they are dispatched, which can happen if we

    // selected scheduler groups which have no ordering guarantees relative to

    // each other (e.g. it moves from scheduler group A for doc group DA to

    // scheduler group B for doc group DB due to changing observers -- if we

    // dispatched the first event on A, and the second on B, we don't know which

    // will execute first.)

    RefPtr<ProgressTracker> tracker = aImage->GetProgressTracker();

    if (tracker) {

      mEventTarget = tracker->GetEventTarget();

    } else {

      mEventTarget = SystemGroup::EventTargetFor(TaskCategory::Other);

    }

  }

}

bool IDecodingTask::IsOnEventTarget() const {

  // This is essentially equivalent to NS_IsOnMainThread() because all of the

  // event targets are for the main thread (although perhaps with a different

  // label / scheduler group). The observers in ProgressTracker may have

  // different event targets from this, so this is just a best effort guess.

  bool current = false;

  mEventTarget->IsOnCurrentThread(¤t;;

  return current;

}

void IDecodingTask::NotifyProgress(NotNull<RasterImage*> aImage,

                                   NotNull<Decoder*> aDecoder) {

  MOZ_ASSERT(aDecoder->HasProgress() && !aDecoder->IsMetadataDecode());

  EnsureHasEventTarget(aImage);

  // Capture the decoder's state. If we need to notify asynchronously, it's

  // important that we don't wait until the lambda actually runs to capture the

  // state that we're going to notify. That would both introduce data races on

  // the decoder's state and cause inconsistencies between the NotifyProgress()

  // calls we make off-main-thread and the notifications that RasterImage

  // actually receives, which would cause bugs.

  Progress progress = aDecoder->TakeProgress();

  IntRect invalidRect = aDecoder->TakeInvalidRect();

  Maybe<uint32_t> frameCount = aDecoder->TakeCompleteFrameCount();

  DecoderFlags decoderFlags = aDecoder->GetDecoderFlags();

  SurfaceFlags surfaceFlags = aDecoder->GetSurfaceFlags();

  // Synchronously notify if we can.

  if (IsOnEventTarget() && !(decoderFlags & DecoderFlags::ASYNC_NOTIFY)) {

    aImage->NotifyProgress(progress, invalidRect, frameCount, decoderFlags,

                           surfaceFlags);

    return;

  }

  // We're forced to notify asynchronously.

  NotNull<RefPtr<RasterImage>> image = aImage;

  mEventTarget->Dispatch(NS_NewRunnableFunction("IDecodingTask::NotifyProgress",

                                                [=]() -> void {

                                                  image->NotifyProgress(

                                                      progress, invalidRect,

                                                      frameCount, decoderFlags,

                                                      surfaceFlags);

                                                }),

                         NS_DISPATCH_NORMAL);

}

void IDecodingTask::NotifyDecodeComplete(NotNull<RasterImage*> aImage,

                                         NotNull<Decoder*> aDecoder) {

  MOZ_ASSERT(aDecoder->HasError() || !aDecoder->InFrame(),

             "Decode complete in the middle of a frame?");

  EnsureHasEventTarget(aImage);

  // Capture the decoder's state.

  DecoderFinalStatus finalStatus = aDecoder->FinalStatus();

  ImageMetadata metadata = aDecoder->GetImageMetadata();

  DecoderTelemetry telemetry = aDecoder->Telemetry();

  Progress progress = aDecoder->TakeProgress();

  IntRect invalidRect = aDecoder->TakeInvalidRect();

  Maybe<uint32_t> frameCount = aDecoder->TakeCompleteFrameCount();

  DecoderFlags decoderFlags = aDecoder->GetDecoderFlags();

  SurfaceFlags surfaceFlags = aDecoder->GetSurfaceFlags();

  // Synchronously notify if we can.

  if (IsOnEventTarget() && !(decoderFlags & DecoderFlags::ASYNC_NOTIFY)) {

    aImage->NotifyDecodeComplete(finalStatus, metadata, telemetry, progress,

                                 invalidRect, frameCount, decoderFlags,

                                 surfaceFlags);

    return;

  }

  // We're forced to notify asynchronously.

  NotNull<RefPtr<RasterImage>> image = aImage;

  mEventTarget->Dispatch(

      NS_NewRunnableFunction("IDecodingTask::NotifyDecodeComplete",

                             [=]() -> void {

                               image->NotifyDecodeComplete(

                                   finalStatus, metadata, telemetry, progress,

                                   invalidRect, frameCount, decoderFlags,

                                   surfaceFlags);

                             }),

      NS_DISPATCH_NORMAL);

}

///////////////////////////////////////////////////////////////////////////////

// IDecodingTask implementation.

///////////////////////////////////////////////////////////////////////////////

void IDecodingTask::Resume() { DecodePool::Singleton()->AsyncRun(this); }

///////////////////////////////////////////////////////////////////////////////

// MetadataDecodingTask implementation.

///////////////////////////////////////////////////////////////////////////////

MetadataDecodingTask::MetadataDecodingTask(NotNull<Decoder*> aDecoder)

    : mMutex("mozilla::image::MetadataDecodingTask"), mDecoder(aDecoder) {

  MOZ_ASSERT(mDecoder->IsMetadataDecode(),

             "Use DecodingTask for non-metadata decodes");

}

void MetadataDecodingTask::Run() {

  MutexAutoLock lock(mMutex);

  LexerResult result = mDecoder->Decode(WrapNotNull(this));

  if (result.is<TerminalState>()) {

    NotifyDecodeComplete(mDecoder->GetImage(), mDecoder);

    return;  // We're done.

  }

  if (result == LexerResult(Yield::NEED_MORE_DATA)) {

    // We can't make any more progress right now. We also don't want to report

    // any progress, because it's important that metadata decode results are

    // delivered atomically. The decoder itself will ensure that we get

    // reenqueued when more data is available; just return for now.

    return;

  }

  MOZ_ASSERT_UNREACHABLE("Metadata decode yielded for an unexpected reason");

}

///////////////////////////////////////////////////////////////////////////////

// AnonymousDecodingTask implementation.

///////////////////////////////////////////////////////////////////////////////

AnonymousDecodingTask::AnonymousDecodingTask(NotNull<Decoder*> aDecoder)

    : mDecoder(aDecoder) {}

void AnonymousDecodingTask::Run() {

  while (true) {

    LexerResult result = mDecoder->Decode(WrapNotNull(this));

    if (result.is<TerminalState>()) {

      return;  // We're done.

    }

    if (result == LexerResult(Yield::NEED_MORE_DATA)) {

      // We can't make any more progress right now. Let the caller decide how to

      // handle it.

      return;

    }

    // Right now we don't do anything special for other kinds of yields, so just

    // keep working.

    MOZ_ASSERT(result.is<Yield>());

  }

}

}  // namespace image

}  // namespace mozilla