squeezelite-esp32/components/spotify/cspot/include/CDNAudioFile.h

#pragma once

#include <cstddef>  // for size_t
#include <cstdint>  // for uint8_t
#include <memory>   // for shared_ptr, unique_ptr
#include <string>   // for string
#include <vector>   // for vector

#include "Crypto.h"      // for Crypto
#include "HTTPClient.h"  // for HTTPClient

namespace bell {
class WrappedSemaphore;
}  // namespace bell

namespace cspot {
class AccessKeyFetcher;

class CDNAudioFile {

 public:
  CDNAudioFile(const std::string& cdnUrl, const std::vector<uint8_t>& audioKey);

  /**
  * @brief Opens connection to the provided cdn url, and fetches track metadata.
  */
  void openStream();

  /**
  * @brief Read and decrypt part of the cdn stream
  *
  * @param dst buffer where to read received data to
  * @param amount of bytes to read
  *
  * @returns amount of bytes read
  */
  size_t readBytes(uint8_t* dst, size_t bytes);

  /**
  * @brief Returns current position in CDN stream
  */
  size_t getPosition();

  /**
  * @brief returns total size of the audio file in bytes
  */
  size_t getSize();

  /**
  * @brief Seeks the track to provided position
  * @param position position where to seek the track
  */
  void seek(size_t position);

 private:
  const int OPUS_HEADER_SIZE = 8 * 1024;
  const int OPUS_FOOTER_PREFFERED = 1024 * 12;  // 12K should be safe
  const int SEEK_MARGIN_SIZE = 1024 * 4;

  const int HTTP_BUFFER_SIZE = 1024 * 14;
  const int SPOTIFY_OPUS_HEADER = 167;

  // Used to store opus metadata, speeds up read
  std::vector<uint8_t> header = std::vector<uint8_t>(OPUS_HEADER_SIZE);
  std::vector<uint8_t> footer;

  // General purpose buffer to read data
  std::vector<uint8_t> httpBuffer = std::vector<uint8_t>(HTTP_BUFFER_SIZE);

  // AES IV for decrypting the audio stream
  const std::vector<uint8_t> audioAESIV = {0x72, 0xe0, 0x67, 0xfb, 0xdd, 0xcb,
                                           0xcf, 0x77, 0xeb, 0xe8, 0xbc, 0x64,
                                           0x3f, 0x63, 0x0d, 0x93};
  std::unique_ptr<Crypto> crypto;

  std::unique_ptr<bell::HTTPClient::Response> httpConnection;

  size_t position = 0;
  size_t totalFileSize = 0;
  size_t lastRequestPosition = 0;
  size_t lastRequestCapacity = 0;

  bool enableRequestMargin = false;

  std::string cdnUrl;
  std::vector<uint8_t> audioKey;

  void decrypt(uint8_t* dst, size_t nbytes, size_t pos);
};
}  // namespace cspot