/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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 <thrift/transport/TTransport.h>
#include <thrift/transport/TVirtualTransport.h>
#include <thrift/TToString.h>
#include <zlib.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 = default;

  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 += to_string(status);
    rv += ")";
    return rv;
  }

  int zlib_status_;
  std::string zlib_msg_;
};

/**
 * This transport uses zlib to compress on write and decompress on read
 *
 * 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.
   * @param comp_level   Compression level (0=none[fast], 6=default, 9=max[slow]).
   */
  TZlibTransport(std::shared_ptr<TTransport> transport,
                 int urbuf_size = DEFAULT_URBUF_SIZE,
                 int crbuf_size = DEFAULT_CRBUF_SIZE,
                 int uwbuf_size = DEFAULT_UWBUF_SIZE,
                 int cwbuf_size = DEFAULT_CWBUF_SIZE,
                 int16_t comp_level = Z_DEFAULT_COMPRESSION)
    : 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),
      comp_level_(comp_level) {
    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"
                                + to_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() const 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 int DEFAULT_URBUF_SIZE = 128;
  static const int DEFAULT_CRBUF_SIZE = 1024;
  static const int DEFAULT_UWBUF_SIZE = 128;
  static const int DEFAULT_CWBUF_SIZE = 1024;

  std::shared_ptr<TTransport> getUnderlyingTransport() const { return transport_; }

protected:
  inline void checkZlibRv(int status, const char* msg);
  inline void checkZlibRvNothrow(int status, const char* msg);
  inline int readAvail() const;
  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 uint32_t MIN_DIRECT_DEFLATE_SIZE = 32;

  std::shared_ptr<TTransport> transport_;

  int urpos_;
  int 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_;

  uint32_t urbuf_size_;
  uint32_t crbuf_size_;
  uint32_t uwbuf_size_;
  uint32_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_;

  const int comp_level_;
};

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

  ~TZlibTransportFactory() override = default;

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

#endif // #ifndef _THRIFT_TRANSPORT_TZLIBTRANSPORT_H_
