/* 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 MEDIAENGINE_REMOTE_VIDEO_SOURCE_H_
#define MEDIAENGINE_REMOTE_VIDEO_SOURCE_H_

#include "CamerasChild.h"
#include "DOMMediaStream.h"
#include "MediaEngineSource.h"
#include "MediaTrackGraph.h"
#include "common_video/include/video_frame_buffer_pool.h"
#include "modules/video_capture/video_capture_defines.h"
#include "mozilla/Mutex.h"
#include "mozilla/dom/MediaStreamTrackBinding.h"

namespace webrtc {
using CaptureCapability = VideoCaptureCapability;
}

namespace mozilla {
namespace dom {
enum class VideoResizeModeEnum : uint8_t;
}

// Fitness distance is defined in
// https://w3c.github.io/mediacapture-main/getusermedia.html#dfn-selectsettings

// In contrast, feasibility distance — used in the implementation of
// crop_and_scale — effectively rounds width and height up to the nearest
// native width and height before calculating distance (sorta).
//
// Another difference is that if the constraint is required
// (min, 'max', or 'exact'), and the settings dictionary's
// value for the constraint does not satisfy the constraint, the fitness
// distance is positive infinity. Given a continuous space of settings
// dictionaries comprising all discrete combinations of dimension and frame-rate
// related properties, the feasibility distance is still in keeping with the
// constraints algorithm.
enum DistanceCalculation { kFitness, kFeasibility };

/**
 * The WebRTC implementation of the MediaEngine interface.
 */
class MediaEngineRemoteVideoSource : public MediaEngineSource,
                                     public camera::FrameRelay {
  ~MediaEngineRemoteVideoSource();

  struct CapabilityCandidate {
    explicit CapabilityCandidate(webrtc::CaptureCapability aCapability,
                                 uint32_t aDistance = 0)
        : mCapability(aCapability), mDistance(aDistance) {}

    const webrtc::CaptureCapability mCapability;
    uint32_t mDistance;
  };

  class CapabilityComparator {
   public:
    bool Equals(const CapabilityCandidate& aCandidate,
                const webrtc::CaptureCapability& aCapability) const {
      return aCandidate.mCapability == aCapability;
    }
  };

  bool ChooseCapability(const NormalizedConstraints& aConstraints,
                        const MediaEnginePrefs& aPrefs,
                        webrtc::CaptureCapability& aCapability,
                        const DistanceCalculation aCalculate,
                        const char** aOutBadConstraint);

  uint32_t GetDistance(const webrtc::CaptureCapability& aCandidate,
                       const NormalizedConstraintSet& aConstraints,
                       const DistanceCalculation aCalculate) const;

  uint32_t GetFitnessDistance(
      const webrtc::CaptureCapability& aCandidate,
      const NormalizedConstraintSet& aConstraints) const;

  uint32_t GetFeasibilityDistance(
      const webrtc::CaptureCapability& aCandidate,
      const NormalizedConstraintSet& aConstraints) const;

  static void TrimLessFitCandidates(nsTArray<CapabilityCandidate>& aSet);

 public:
  explicit MediaEngineRemoteVideoSource(const MediaDevice* aMediaDevice);

  static already_AddRefed<MediaEngineRemoteVideoSource> CreateFrom(
      const MediaEngineRemoteVideoSource* aSource,
      const MediaDevice* aMediaDevice);

  // ExternalRenderer
  /**
   * Signals that the capture stream has ended
   **/
  void OnCaptureEnded() override;
  int DeliverFrame(uint8_t* aBuffer,
                   const camera::VideoFrameProperties& aProps) override;

  // MediaEngineSource
  nsresult Allocate(const dom::MediaTrackConstraints& aConstraints,
                    const MediaEnginePrefs& aPrefs, uint64_t aWindowID,
                    const char** aOutBadConstraint) override;
  nsresult Deallocate() override;
  void SetTrack(const RefPtr<MediaTrack>& aTrack,
                const PrincipalHandle& aPrincipal) override;
  nsresult Start() override;
  nsresult Reconfigure(const dom::MediaTrackConstraints& aConstraints,
                       const MediaEnginePrefs& aPrefs,
                       const char** aOutBadConstraint) override;
  nsresult FocusOnSelectedSource() override;
  nsresult Stop() override;

  nsresult StartCapture(const NormalizedConstraints& aConstraints,
                        const dom::VideoResizeModeEnum& aResizeMode);
  uint32_t GetBestFitnessDistance(
      const nsTArray<const NormalizedConstraintSet*>& aConstraintSets,
      const MediaEnginePrefs& aPrefs) const override;
  void GetSettings(dom::MediaTrackSettings& aOutSettings) const override;

  RefPtr<GenericNonExclusivePromise> GetFirstFramePromise() const override {
    return mFirstFramePromise;
  }

  const TrackingId& GetTrackingId() const override;

  static camera::CaptureEngine CaptureEngine(dom::MediaSourceEnum aMediaSource);

  MediaEventSource<void>* CaptureEndedEvent() override {
    return &mCaptureEndedEvent;
  }

  void GetCapabilities(
      dom::MediaTrackCapabilities& aOutCapabilities) const override;

 private:
  /**
   * Returns the number of capabilities for the underlying device.
   *
   * Guaranteed to return at least one capability.
   */
  size_t NumCapabilities() const;

  /**
   * Returns the capability with index `aIndex` for our assigned device.
   *
   * It is an error to call this with `aIndex >= NumCapabilities()`.
   *
   * The lifetime of the returned capability is the same as for this source.
   */
  webrtc::CaptureCapability& GetCapability(size_t aIndex) const;

  int mCaptureId = -1;
  const camera::CaptureEngine mCapEngine;  // source of media (cam, screen etc)

  // A tracking id used to uniquely identify the source of video frames.
  // Set under mMutex on the owning thread. Accessed under one of the two.
  TrackingId mTrackingId;

  // Mirror of mTrackingId on the frame-delivering thread (Cameras IPC).
  Maybe<TrackingId> mFrameDeliveringTrackingId;

  // mMutex protects certain members on 3 threads:
  // MediaManager, Cameras IPC and MediaTrackGraph.
  mutable Mutex mMutex MOZ_UNANNOTATED;

  // Current state of this source.
  // Set under mMutex on the owning thread. Accessed under one of the two.
  MediaEngineSourceState mState = kReleased;

  // The source track that we feed video data to.
  // Set under mMutex on the owning thread. Accessed under one of the two.
  RefPtr<SourceMediaTrack> mTrack;

  // The PrincipalHandle that gets attached to the frames we feed to mTrack.
  // Set under mMutex on the owning thread. Accessed under one of the two.
  PrincipalHandle mPrincipal = PRINCIPAL_HANDLE_NONE;

  // Set in Start() and Deallocate() on the owning thread.
  // Accessed in DeliverFrame() on the camera IPC thread, guaranteed to happen
  // after Start() and before the end of Stop().
  RefPtr<layers::ImageContainer> mImageContainer;

  // A buffer pool used to manage the temporary buffer used when rescaling
  // incoming images. Cameras IPC thread only.
  webrtc::VideoFrameBufferPool mRescalingBufferPool;

  // The intrinsic size of the latest received image, before cropping and
  // scaling down. So we can provide a decent guess to settings for desktop
  // sources, since they don't provide capabilities.
  // Set under mMutex on the Cameras IPC thread. Accessed under one of the two.
  gfx::IntSize mIncomingImageSize = gfx::IntSize(0, 0);

  // The intrinsic size of the latest processed image, after cropping and
  // scaling down. So we can update settings on main thread in response to size
  // changes.
  // Set under mMutex on the Cameras IPC thread. Accessed under one of the two.
  gfx::IntSize mScaledImageSize = gfx::IntSize(0, 0);

  struct AtomicBool {
    Atomic<bool> mValue;
  };

  // True when resolution settings have been updated from a real frame's
  // resolution. Threadsafe. Set to false on the owning thread. Set to true on
  // main thread.
  const RefPtr<media::Refcountable<AtomicBool>> mSettingsUpdatedByFrame;

  // The current settings of this source.
  // Note that these may be different from the settings of the underlying device
  // since we scale frames to avoid fingerprinting.
  // Members are main thread only.
  const RefPtr<media::Refcountable<dom::MediaTrackSettings>> mSettings;
  const RefPtr<media::Refcountable<dom::MediaTrackCapabilities>>
      mTrackCapabilities;
  MozPromiseHolder<GenericNonExclusivePromise> mFirstFramePromiseHolder;
  RefPtr<GenericNonExclusivePromise> mFirstFramePromise;

  // The capability currently chosen by constraints of the user of this source,
  // and the distance calculation used when applying them.
  // Set under mMutex on the owning thread. Accessed under one of the two.
  webrtc::CaptureCapability mCapability;
  DistanceCalculation mCalculation;

  // The constraints we're currently operating under, for calculating incoming
  // video resolution.
  Maybe<NormalizedConstraints> mConstraints MOZ_GUARDED_BY(mMutex);

  // Owning thread only.
  UniquePtr<MediaEnginePrefs> mPrefs;

  /**
   * Capabilities that we choose between when applying constraints.
   *
   * This allows for memoization of capabilities as they're requested from the
   * parent process.
   *
   * This is mutable so that the const methods NumCapabilities() and
   * GetCapability() can reset it. Owning thread only.
   */
  mutable nsTArray<UniquePtr<webrtc::CaptureCapability>> mCapabilities;

  /**
   * True if mCapabilities only contains hardcoded capabilities. This can happen
   * if the underlying device is not reporting any capabilities. These can be
   * affected by constraints, so they're evaluated in ChooseCapability() rather
   * than GetCapability().
   *
   * This is mutable so that the const methods NumCapabilities() and
   * GetCapability() can reset it. Owning thread only.
   */
  mutable bool mCapabilitiesAreHardcoded = false;

  const RefPtr<const MediaDevice> mMediaDevice;
  const nsCString mDeviceUUID;
  Maybe<nsString> mFacingMode;
  MediaEventProducer<void> mCaptureEndedEvent;
};

}  // namespace mozilla

#endif /* MEDIAENGINE_REMOTE_VIDEO_SOURCE_H_ */