/* -*- 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/. */

#ifndef mozilla_image_ProgressTracker_h

#define mozilla_image_ProgressTracker_h

#include "CopyOnWrite.h"

#include "mozilla/NotNull.h"

#include "mozilla/Mutex.h"

#include "mozilla/RefPtr.h"

#include "mozilla/WeakPtr.h"

#include "nsDataHashtable.h"

#include "nsCOMPtr.h"

#include "nsTObserverArray.h"

#include "nsThreadUtils.h"

#include "nsRect.h"

#include "IProgressObserver.h"

class nsIRunnable;

namespace mozilla {

namespace image {

class AsyncNotifyRunnable;

class AsyncNotifyCurrentStateRunnable;

class Image;

/**

 * Image progress bitflags.

 *

 * See CheckProgressConsistency() for the invariants we enforce about the

 * ordering dependencies betweeen these flags.

 */

enum {

  FLAG_SIZE_AVAILABLE = 1u << 0,    // STATUS_SIZE_AVAILABLE

  FLAG_DECODE_COMPLETE = 1u << 1,   // STATUS_DECODE_COMPLETE

  FLAG_FRAME_COMPLETE = 1u << 2,    // STATUS_FRAME_COMPLETE

  FLAG_LOAD_COMPLETE = 1u << 3,     // STATUS_LOAD_COMPLETE

  FLAG_IS_ANIMATED = 1u << 6,       // STATUS_IS_ANIMATED

  FLAG_HAS_TRANSPARENCY = 1u << 7,  // STATUS_HAS_TRANSPARENCY

  FLAG_LAST_PART_COMPLETE = 1u << 8,

  FLAG_HAS_ERROR = 1u << 9  // STATUS_ERROR

};

typedef uint32_t Progress;

const uint32_t NoProgress = 0;

inline Progress LoadCompleteProgress(bool aLastPart, bool aError,

                                     nsresult aStatus) {

  Progress progress = FLAG_LOAD_COMPLETE;

  if (aLastPart) {

    progress |= FLAG_LAST_PART_COMPLETE;

  }

  if (NS_FAILED(aStatus) || aError) {

    progress |= FLAG_HAS_ERROR;

  }

  return progress;

}

/**

 * ProgressTracker stores its observers in an ObserverTable, which is a hash

 * table mapping raw pointers to WeakPtr's to the same objects. This sounds like

 * unnecessary duplication of information, but it's necessary for stable hash

 * values since WeakPtr's lose the knowledge of which object they used to point

 * to when that object is destroyed.

 *

 * ObserverTable subclasses nsDataHashtable to add reference counting support

 * and a copy constructor, both of which are needed for use with CopyOnWrite<T>.

 */

class ObserverTable : public nsDataHashtable<nsPtrHashKey<IProgressObserver>,

                                             WeakPtr<IProgressObserver>> {

 public:

  NS_INLINE_DECL_REFCOUNTING(ObserverTable);

  ObserverTable() = default;

  ObserverTable(const ObserverTable& aOther) {

    NS_WARNING("Forced to copy ObserverTable due to nested notifications");

    for (auto iter = aOther.ConstIter(); !iter.Done(); iter.Next()) {

      this->Put(iter.Key(), iter.Data());

    }

  }

 private:

  ~ObserverTable() {}

};

/**

 * ProgressTracker is a class that records an Image's progress through the

 * loading and decoding process, and makes it possible to send notifications to

 * IProgressObservers, both synchronously and asynchronously.

 *

 * When a new observer needs to be notified of the current progress of an image,

 * call the Notify() method on this class with the relevant observer as its

 * argument, and the notifications will be replayed to the observer

 * asynchronously.

 */

class ProgressTracker : public mozilla::SupportsWeakPtr<ProgressTracker> {

  virtual ~ProgressTracker() {}

 public:

  MOZ_DECLARE_WEAKREFERENCE_TYPENAME(ProgressTracker)

  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ProgressTracker)

  ProgressTracker();

  bool HasImage() const {

    MutexAutoLock lock(mMutex);

    return mImage;

  }

  already_AddRefed<Image> GetImage() const {

    MutexAutoLock lock(mMutex);

    RefPtr<Image> image = mImage;

    return image.forget();

  }

  // Get the current image status (as in imgIRequest).

  uint32_t GetImageStatus() const;

  // Get the current Progress.

  Progress GetProgress() const { return mProgress; }

  // Schedule an asynchronous "replaying" of all the notifications that would

  // have to happen to put us in the current state.

  // We will also take note of any notifications that happen between the time

  // Notify() is called and when we call SyncNotify on |aObserver|, and replay

  // them as well.

  // Should be called on the main thread only, since observers and GetURI are

  // not threadsafe.

  void Notify(IProgressObserver* aObserver);

  // Schedule an asynchronous "replaying" of all the notifications that would

  // have to happen to put us in the state we are in right now.

  // Unlike Notify(), does *not* take into account future notifications.

  // This is only useful if you do not have an imgRequest, e.g., if you are a

  // static request returned from imgIRequest::GetStaticRequest().

  // Should be called on the main thread only, since observers and GetURI are

  // not threadsafe.

  void NotifyCurrentState(IProgressObserver* aObserver);

  // "Replay" all of the notifications that would have to happen to put us in

  // the state we're currently in.

  // Only use this if you're already servicing an asynchronous call (e.g.

  // OnStartRequest).

  // Should be called on the main thread only, since observers and GetURI are

  // not threadsafe.

  void SyncNotify(IProgressObserver* aObserver);

  // Get this ProgressTracker ready for a new request. This resets all the

  // state that doesn't persist between requests.

  void ResetForNewRequest();

  // Stateless notifications. These are dispatched and immediately forgotten

  // about. All of these notifications are main thread only.

  void OnDiscard();

  void OnUnlockedDraw();

  void OnImageAvailable();

  // Compute the difference between this our progress and aProgress. This allows

  // callers to predict whether SyncNotifyProgress will send any notifications.

  Progress Difference(Progress aProgress) const {

    return ~mProgress & aProgress;

  }

  // Update our state to incorporate the changes in aProgress and synchronously

  // notify our observers.

  //

  // Because this may result in recursive notifications, no decoding locks may

  // be held.  Called on the main thread only.

  void SyncNotifyProgress(Progress aProgress,

                          const nsIntRect& aInvalidRect = nsIntRect());

  // We manage a set of observers that are using an image and thus concerned

  // with its loading progress. Weak pointers.

  void AddObserver(IProgressObserver* aObserver);

  bool RemoveObserver(IProgressObserver* aObserver);

  uint32_t ObserverCount() const;

  // Get the event target we should currently dispatch events to.

  already_AddRefed<nsIEventTarget> GetEventTarget() const;

  // Resets our weak reference to our image. Image subclasses should call this

  // in their destructor.

  void ResetImage();

  // Tell this progress tracker that it is for a multipart image.

  void SetIsMultipart() { mIsMultipart = true; }

 private:

  friend class AsyncNotifyRunnable;

  friend class AsyncNotifyCurrentStateRunnable;

  friend class ImageFactory;

  ProgressTracker(const ProgressTracker& aOther) = delete;

  // Sets our weak reference to our image. Only ImageFactory should call this.

  void SetImage(Image* aImage);

  // Send some notifications that would be necessary to make |aObserver| believe

  // the request is finished downloading and decoding.  We only send

  // FLAG_LOAD_COMPLETE and FLAG_ONLOAD_UNBLOCKED, and only if necessary.

  void EmulateRequestFinished(IProgressObserver* aObserver);

  // Main thread only because it deals with the observer service.

  void FireFailureNotification();

  // The runnable, if any, that we've scheduled to deliver async notifications.

  nsCOMPtr<nsIRunnable> mRunnable;

  // mMutex protects access to mImage and mEventTarget.

  mutable Mutex mMutex;

  // mImage is a weak ref; it should be set to null when the image goes out of

  // scope.

  Image* mImage;

  // mEventTarget is the current, best effort event target to dispatch

  // notifications to from the decoder threads. It will change as observers are

  // added and removed (see mObserversWithTargets).

  NotNull<nsCOMPtr<nsIEventTarget>> mEventTarget;

  // How many observers have been added that have an explicit event target.

  // When the first observer is added with an explicit event target, we will

  // default to that as long as all observers use the same target. If a new

  // observer is added which has a different event target, we will switch to

  // using the unlabeled main thread event target which is safe for all

  // observers. If all observers with explicit event targets are removed, we

  // will revert back to the initial event target (for SystemGroup). An

  // observer without an explicit event target does not care what context it

  // is dispatched in, and thus does not impact the state.

  uint32_t mObserversWithTargets;

  // Hashtable of observers attached to the image. Each observer represents a

  // consumer using the image. Main thread only.

  CopyOnWrite<ObserverTable> mObservers;

  Progress mProgress;

  // Whether this is a progress tracker for a multipart image.

  bool mIsMultipart;

};

}  // namespace image

}  // namespace mozilla

#endif  // mozilla_image_ProgressTracker_h