/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef _THRIFT_TRANSPORT_TZLIBTRANSPORT_H_
#define _THRIFT_TRANSPORT_TZLIBTRANSPORT_H_ 1

#include <boost/lexical_cast.hpp>
#include <thrift/lib/cpp/transport/TBufferTransports.h>
#include <thrift/lib/cpp/transport/TVirtualTransport.h>

struct z_stream_s;

namespace apache {
namespace thrift {
namespace transport {

class TZlibTransportException : public TTransportException {
 public:
  TZlibTransportException(int status, const char* msg)
      : TTransportException(
            TTransportException::INTERNAL_ERROR, errorMessage(status, msg)),
        zlib_status_(status),
        zlib_msg_(msg == nullptr ? "(null)" : msg) {}

  ~TZlibTransportException() noexcept override {}

  int getZlibStatus() { return zlib_status_; }
  std::string getZlibMessage() { return zlib_msg_; }

  static std::string errorMessage(int status, const char* msg) {
    std::string rv = "zlib error: ";
    if (msg) {
      rv += msg;
    } else {
      rv += "(no message)";
    }
    rv += " (status = ";
    rv += boost::lexical_cast<std::string>(status);
    rv += ")";
    return rv;
  }

  int zlib_status_;
  std::string zlib_msg_;
};

/**
 * This transport uses zlib's compressed format on the "far" side.
 *
 * There are two kinds of TZlibTransport objects:
 * - Standalone objects are used to encode self-contained chunks of data
 *   (like structures).  They include checksums.
 * - Non-standalone transports are used for RPC.  They are not implemented yet.
 *
 * TODO(dreiss): Don't do an extra copy of the compressed data if
 *               the underlying transport is TBuffered or TMemory.
 *
 */
class TZlibTransport : public TVirtualTransport<TZlibTransport> {
 public:
  /**
   * @param transport    The transport to read compressed data from
   *                     and write compressed data to.
   * @param urbuf_size   Uncompressed buffer size for reading.
   * @param crbuf_size   Compressed buffer size for reading.
   * @param uwbuf_size   Uncompressed buffer size for writing.
   * @param cwbuf_size   Compressed buffer size for writing.
   *
   * TODO(dreiss): Write a constructor that isn't a pain.
   */
  explicit TZlibTransport(
      std::shared_ptr<TTransport> transport,
      size_t urbuf_size = DEFAULT_URBUF_SIZE,
      size_t crbuf_size = DEFAULT_CRBUF_SIZE,
      size_t uwbuf_size = DEFAULT_UWBUF_SIZE,
      size_t cwbuf_size = DEFAULT_CWBUF_SIZE)
      : transport_(transport),
        urpos_(0),
        uwpos_(0),
        input_ended_(false),
        output_finished_(false),
        urbuf_size_(urbuf_size),
        crbuf_size_(crbuf_size),
        uwbuf_size_(uwbuf_size),
        cwbuf_size_(cwbuf_size),
        urbuf_(nullptr),
        crbuf_(nullptr),
        uwbuf_(nullptr),
        cwbuf_(nullptr),
        rstream_(nullptr),
        wstream_(nullptr) {
    if (uwbuf_size_ < MIN_DIRECT_DEFLATE_SIZE) {
      // Have to copy this into a local because of a linking issue.
      int minimum = MIN_DIRECT_DEFLATE_SIZE;
      throw TTransportException(
          TTransportException::BAD_ARGS,
          "TZLibTransport: uncompressed write buffer must be at least" +
              boost::lexical_cast<std::string>(minimum) + ".");
    }

    try {
      urbuf_ = new uint8_t[urbuf_size];
      crbuf_ = new uint8_t[crbuf_size];
      uwbuf_ = new uint8_t[uwbuf_size];
      cwbuf_ = new uint8_t[cwbuf_size];

      // Don't call this outside of the constructor.
      initZlib();

    } catch (...) {
      delete[] urbuf_;
      delete[] crbuf_;
      delete[] uwbuf_;
      delete[] cwbuf_;
      throw;
    }
  }

  // Don't call this outside of the constructor.
  void initZlib();

  /**
   * TZlibTransport destructor.
   *
   * Warning: Destroying a TZlibTransport object may discard any written but
   * unflushed data.  You must explicitly call flush() or finish() to ensure
   * that data is actually written and flushed to the underlying transport.
   */
  ~TZlibTransport() override;

  bool isOpen() override;
  bool peek() override;

  void open() override { transport_->open(); }

  void close() override { transport_->close(); }

  uint32_t read(uint8_t* buf, uint32_t len);

  void write(const uint8_t* buf, uint32_t len);

  void flush() override;

  /**
   * Finalize the zlib stream.
   *
   * This causes zlib to flush any pending write data and write end-of-stream
   * information, including the checksum.  Once finish() has been called, no
   * new data can be written to the stream.
   */
  void finish();

  const uint8_t* borrow(uint8_t* buf, uint32_t* len);

  void consume(uint32_t len);

  /**
   * Verify the checksum at the end of the zlib stream.
   *
   * This may only be called after all data has been read.
   * It verifies the checksum that was written by the finish() call.
   */
  void verifyChecksum();

  /**
   * TODO(someone_smart): Choose smart defaults.
   */
  static const size_t DEFAULT_URBUF_SIZE = 128;
  static const size_t DEFAULT_CRBUF_SIZE = 1024;
  static const size_t DEFAULT_UWBUF_SIZE = 128;
  static const size_t DEFAULT_CWBUF_SIZE = 1024;

 protected:
  inline void checkZlibRv(int status, const char* msg);
  inline void checkZlibRvNothrow(int status, const char* msg);
  inline size_t readAvail();
  void flushToTransport(int flush);
  void flushToZlib(const uint8_t* buf, int len, int flush);
  bool readFromZlib();

 protected:
  // Writes smaller than this are buffered up.
  // Larger (or equal) writes are dumped straight to zlib.
  static const size_t MIN_DIRECT_DEFLATE_SIZE = 32;

  std::shared_ptr<TTransport> transport_;

  size_t urpos_;
  size_t uwpos_;

  /// True iff zlib has reached the end of the input stream.
  bool input_ended_;
  /// True iff we have finished the output stream.
  bool output_finished_;

  size_t urbuf_size_;
  size_t crbuf_size_;
  size_t uwbuf_size_;
  size_t cwbuf_size_;

  uint8_t* urbuf_;
  uint8_t* crbuf_;
  uint8_t* uwbuf_;
  uint8_t* cwbuf_;

  struct z_stream_s* rstream_;
  struct z_stream_s* wstream_;
};

/**
 * Wraps a transport into a zlibbed one.
 *
 */
class TZlibTransportFactory : public TTransportFactory {
 public:
  TZlibTransportFactory() {}

  ~TZlibTransportFactory() override {}

  std::shared_ptr<TTransport> getTransport(
      std::shared_ptr<TTransport> trans) override {
    return std::shared_ptr<TTransport>(new TZlibTransport(trans));
  }
};

/**
 * Wraps a transport into a framed, zlibbed one.
 */
class TFramedZlibTransportFactory : public TTransportFactory {
 public:
  TFramedZlibTransportFactory() {}

  ~TFramedZlibTransportFactory() override {}

  std::shared_ptr<TTransport> getTransport(
      std::shared_ptr<TTransport> trans) override {
    std::shared_ptr<TTransport> framedTransport(new TFramedTransport(trans));
    return std::shared_ptr<TTransport>(new TZlibTransport(framedTransport));
  }
};

} // namespace transport
} // namespace thrift
} // namespace apache

#endif // #ifndef _THRIFT_TRANSPORT_TZLIBTRANSPORT_H_
