#pragma once

#include "envoy/compression/decompressor/decompressor.h"

#include "envoy/stats/scope.h"

#include "envoy/stats/stats_macros.h"

#include "source/common/common/logger.h"

#include "source/extensions/compression/gzip/common/base.h"

#include "zlib.h"

namespace Envoy {

namespace Extensions {

namespace Compression {

namespace Gzip {

namespace Decompressor {

/**

 * All zlib decompressor stats. @see stats_macros.h

 */

#define ALL_ZLIB_DECOMPRESSOR_STATS(COUNTER)                                                       \

/**

 * Struct definition for zlib decompressor stats. @see stats_macros.h

 */

struct ZlibDecompressorStats {

  ALL_ZLIB_DECOMPRESSOR_STATS(GENERATE_COUNTER_STRUCT)

};

/**

 * Implementation of decompressor's interface.

 */

class ZlibDecompressorImpl : public Common::Base,

                             public Envoy::Compression::Decompressor::Decompressor,

                             public Logger::Loggable<Logger::Id::decompression> {

public:

  /**

   * Constructor that allows setting the size of decompressor's output buffer. It

   * should be called whenever a buffer size different than the 4096 bytes, normally set by the

   * default constructor, is desired. If memory is available and it makes sense to output large

   * chunks of compressed data, zlib documentation suggests buffers sizes on the order of 128K or

   * 256K bytes. @see http://zlib.net/zlib_how.html

   * @param chunk_size amount of memory reserved for the decompressor output.

   */

  ZlibDecompressorImpl(Stats::Scope& scope, const std::string& stats_prefix, uint64_t chunk_size,

                       uint64_t max_inflate_ratio);

  /**

   * Init must be called in order to initialize the decompressor. Once decompressor is initialized,

   * it cannot be initialized again. Init should run before decompressing any data.

   * @param window_bits sets the size of the history buffer. It must be greater than or equal to

   * the window_bits value provided when data was compressed (zlib manual).

   */

  void init(int64_t window_bits);

  // Compression::Decompressor::Decompressor

  void decompress(const Buffer::Instance& input_buffer, Buffer::Instance& output_buffer) override;

  // Flag to track whether error occurred during decompression.

  // When an error occurs, the error code (a negative int) will be stored in this variable.

  int decompression_error_{0};

private:

  // TODO: clean up friend class. This is here to allow coverage of chargeErrorStats as it isn't

  // completely straightforward

  // to cause zlib's inflate function to return all the error codes necessary to hit all the cases

  // in the switch statement.

  friend class ZlibDecompressorStatsTest;

  bool inflateNext();

  void chargeErrorStats(const int result);

  const ZlibDecompressorStats stats_;

  const uint64_t max_inflate_ratio_;

};

} // namespace Decompressor

} // namespace Gzip

} // namespace Compression

} // namespace Extensions

} // namespace Envoy