// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_FORMATS_MPEG_MPEG_AUDIO_STREAM_PARSER_BASE_H_
#define MEDIA_FORMATS_MPEG_MPEG_AUDIO_STREAM_PARSER_BASE_H_

#include <stdint.h>

#include <memory>
#include <optional>
#include <set>
#include <vector>

#include "base/functional/callback.h"
#include "base/memory/raw_ptr.h"
#include "media/base/audio_decoder_config.h"
#include "media/base/audio_timestamp_helper.h"
#include "media/base/bit_reader.h"
#include "media/base/byte_queue.h"
#include "media/base/media_export.h"
#include "media/base/stream_parser.h"

namespace media {

namespace formats::mpeg {
struct MpegAudioHeaderInfo;
}  // namespace formats::mpeg

class MEDIA_EXPORT MPEGAudioStreamParserBase : public StreamParser {
 public:
  struct Header {
    // Size of the frame in bytes, including the frame header.
    size_t frame_size = 0;

    // Sample rate of the frame in Hz.
    int sample_rate = 0;

    // Channel layout configuration.
    ChannelLayout channel_layout = CHANNEL_LAYOUT_NONE;

    // Number of samples per frame.
    int sample_count = 0;

    // Set to true if the frame has valid header values, but no usable
    // encoded data (e.g., silent XING metadata frames). If true, the
    // base parser will discard the frame after consuming its metadata.
    bool metadata_frame = false;

    // Subclass-specific extra data configurations (e.g., AudioSpecificConfig).
    std::vector<uint8_t> extra_data;
  };
  // |start_code_mask| is used to find the start of each frame header.  Also
  // referred to as the sync code in the MP3 and ADTS header specifications.
  // |codec_delay| is the number of samples the decoder will output before the
  // first real frame.
  MPEGAudioStreamParserBase(uint32_t start_code_mask,
                            AudioCodec audio_codec,
                            int codec_delay);

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

  ~MPEGAudioStreamParserBase() override;

  // StreamParser implementation.
  void Init(InitCB init_cb,
            NewConfigCB config_cb,
            NewBuffersCB new_buffers_cb,
            EncryptedMediaInitDataCB encrypted_media_init_data_cb,
            NewMediaSegmentCB new_segment_cb,
            EndMediaSegmentCB end_of_segment_cb,
            MediaLog* media_log) override;
  void Flush() override;
  bool GetGenerateTimestampsFlag() const override;
  [[nodiscard]] bool AppendToParseBuffer(
      base::span<const uint8_t> buf) override;
  [[nodiscard]] ParseStatus Parse(int max_pending_bytes_to_inspect) override;

 protected:
  // Returns the minimum header size required to parse a frame header.
  virtual size_t GetMinHeaderSize() const = 0;

  // Parses the frame header. Returns std::nullopt if parsing failed.
  virtual std::optional<Header> ParseFrameHeader(
      base::span<const uint8_t> data) = 0;

  // Converts a Rust FFI header info struct into the C++ parser Header struct.
  virtual Header FfiHeaderToHeader(
      const formats::mpeg::MpegAudioHeaderInfo& ffi_header) const = 0;

  MediaLog* media_log() const { return media_log_.get(); }

 private:
  enum State {
    UNINITIALIZED,
    INITIALIZED,
    PARSE_ERROR
  };

  ParseStatus ParseRust(int max_pending_bytes_to_inspect);
  ParseStatus ParseLegacy(int max_pending_bytes_to_inspect);

  bool ProcessAudioFrame(const Header& header,
                         base::span<const uint8_t> data,
                         BufferQueue* buffers);

  void ChangeState(State state);

  // Parsing functions for various byte stream elements.  |data| & |size|
  // describe the data available for parsing.
  //
  // Returns:
  // > 0 : The number of bytes parsed.
  //   0 : If more data is needed to parse the entire element.
  // < 0 : An error was encountered during parsing.
  int ParseFrame(base::span<const uint8_t> data, BufferQueue* buffers);
  int ParseIcecastHeader(const uint8_t* data, int size);
  int ParseID3v1(const uint8_t* data, int size);
  int ParseID3v2(const uint8_t* data, int size);

  // Parses an ID3v2 "sync safe" integer.
  // |reader| - A BitReader to read from.
  // |value| - Set to the integer value read, if true is returned.
  //
  // Returns true if the integer was successfully parsed and |value|
  // was set.
  // Returns false if an error was encountered. The state of |value| is
  // undefined when false is returned.
  bool ParseSyncSafeInt(BitReader* reader, int32_t* value);

  // Scans |data| for the next valid start code.
  // Returns:
  // > 0 : The number of bytes that should be skipped to reach the
  //       next start code..
  //   0 : If a valid start code was not found and more data is needed.
  // < 0 : An error was encountered during parsing.
  int FindNextValidStartCode(const uint8_t* data, int size);

  // Sends the buffers in |buffers| to |new_buffers_cb_| and then clears
  // |buffers|.
  // If |end_of_segment| is set to true, then |end_of_segment_cb_| is called
  // after |new_buffers_cb_| to signal that these buffers represent the end of a
  // media segment.
  // Returns true if the buffers are sent successfully.
  bool SendBuffers(BufferQueue* buffers, bool end_of_segment);

  State state_ = UNINITIALIZED;

  InitCB init_cb_;
  NewConfigCB config_cb_;
  NewBuffersCB new_buffers_cb_;
  NewMediaSegmentCB new_segment_cb_;
  EndMediaSegmentCB end_of_segment_cb_;
  std::unique_ptr<MediaLog> media_log_;

  // Tracks how much data has not yet been attempted to be parsed from `queue_`
  // between calls to Parse(). AppendToParseBuffer() increases this from 0 as
  // more data is added. Parse() incrementally reduces this and Flush() zeroes
  // this. Note that Parse() may have inspected some data at the front of
  // `queue_` but not yet been able to pop it from the queue. So this value may
  // be lower than the actual amount of bytes in `queue_`, since more data is
  // needed to complete the parse.
  int uninspected_pending_bytes_ = 0;
  ByteQueue queue_;

  AudioDecoderConfig config_;
  std::unique_ptr<AudioTimestampHelper> timestamp_helper_;
  bool in_media_segment_ = false;
  const uint32_t start_code_mask_;
  const AudioCodec audio_codec_;
  const int codec_delay_;
};

}  // namespace media

#endif  // MEDIA_FORMATS_MPEG_MPEG_AUDIO_STREAM_PARSER_BASE_H_