// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_FILTERS_DECRYPTING_AUDIO_DECODER_H_
#define MEDIA_FILTERS_DECRYPTING_AUDIO_DECODER_H_

#include <memory>

#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"
#include "media/base/audio_decoder.h"
#include "media/base/callback_registry.h"
#include "media/base/cdm_context.h"
#include "media/base/decryptor.h"
#include "media/base/demuxer_stream.h"

namespace base {
class SequencedTaskRunner;
}

namespace media {

class AudioTimestampHelper;
class DecoderBuffer;
class Decryptor;
class MediaLog;

// Decryptor-based AudioDecoder implementation that can decrypt and decode
// encrypted audio buffers and return decrypted and decompressed audio frames.
// All public APIs and callbacks are trampolined to the |task_runner_| so
// that no locks are required for thread safety.
class MEDIA_EXPORT DecryptingAudioDecoder : public AudioDecoder {
 public:
  DecryptingAudioDecoder(
      const scoped_refptr<base::SequencedTaskRunner>& task_runner,
      MediaLog* media_log);

  DecryptingAudioDecoder(const DecryptingAudioDecoder&) = delete;
  DecryptingAudioDecoder& operator=(const DecryptingAudioDecoder&) = delete;

  ~DecryptingAudioDecoder() override;

  // Decoder implementation
  bool SupportsDecryption() const override;
  AudioDecoderType GetDecoderType() const override;

  // AudioDecoder implementation.
  void Initialize(const AudioDecoderConfig& config,
                  CdmContext* cdm_context,
                  InitCB init_cb,
                  const OutputCB& output_cb,
                  const WaitingCB& waiting_cb) override;
  void Decode(scoped_refptr<DecoderBuffer> buffer, DecodeCB decode_cb) override;
  void Reset(base::OnceClosure closure) override;

 private:
  // For a detailed state diagram please see this link: http://goo.gl/8jAok
  // TODO(xhwang): Add a ASCII state diagram in this file after this class
  // stabilizes.
  // TODO(xhwang): Update this diagram for DecryptingAudioDecoder.
  enum State {
    kUninitialized = 0,
    kPendingDecoderInit,
    kIdle,
    kPendingDecode,
    kWaitingForKey,
    kDecodeFinished,
    kError
  };

  // Initializes the audio decoder on the |decryptor_| with |config_|.
  void InitializeDecoder();

  // Callback for Decryptor::InitializeAudioDecoder() during initialization.
  void FinishInitialization(bool success);

  void DecodePendingBuffer();

  // Callback for Decryptor::DecryptAndDecodeAudio().
  void DeliverFrame(int buffer_size,
                    Decryptor::Status status,
                    const Decryptor::AudioFrames& frames);

  // Callback for the CDM to notify |this|.
  void OnCdmContextEvent(CdmContext::Event event);

  // Resets decoder and calls |reset_cb_|.
  void DoReset();

  // Sets timestamps for |frames| and then passes them to |output_cb_|.
  void ProcessDecodedFrames(const Decryptor::AudioFrames& frames);

  // Set in constructor.
  scoped_refptr<base::SequencedTaskRunner> const task_runner_;
  MediaLog* const media_log_;

  State state_ = kUninitialized;

  InitCB init_cb_;
  OutputCB output_cb_;
  DecodeCB decode_cb_;
  base::OnceClosure reset_cb_;
  WaitingCB waiting_cb_;

  // The current decoder configuration.
  AudioDecoderConfig config_;

  Decryptor* decryptor_ = nullptr;

  // The buffer that needs decrypting/decoding.
  scoped_refptr<media::DecoderBuffer> pending_buffer_to_decode_;

  // Indicates the situation where new key is added during pending decode
  // (in other words, this variable can only be set in state kPendingDecode).
  // If this variable is true and kNoKey is returned then we need to try
  // decrypting/decoding again in case the newly added key is the correct
  // decryption key.
  bool key_added_while_decode_pending_ = false;

  std::unique_ptr<AudioTimestampHelper> timestamp_helper_;

  // Once Initialized() with encrypted content support, if the stream changes to
  // clear content, we want to ensure this decoder remains used.
  bool support_clear_content_ = false;

  // To keep the CdmContext event callback registered.
  std::unique_ptr<CallbackRegistration> event_cb_registration_;

  base::WeakPtrFactory<DecryptingAudioDecoder> weak_factory_{this};
};

}  // namespace media

#endif  // MEDIA_FILTERS_DECRYPTING_AUDIO_DECODER_H_