// Copyright 2019-2020 CERN and copyright holders of ALICE O2.
// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
// All rights not expressly granted are reserved.
//
// This software is distributed under the terms of the GNU General Public
// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
//
// In applying this license CERN does not waive the privileges and immunities
// granted to it by virtue of its status as an Intergovernmental Organization
// or submit itself to any jurisdiction.

/// @file   Encoder.h
/// @author Michael Lettrich
/// @since  2020-04-06
/// @brief  Encoder - code symbol into a rANS encoded state

#ifndef RANS_ENCODER_H
#define RANS_ENCODER_H

#include <memory>
#include <algorithm>
#include <iomanip>

#include <fairlogger/Logger.h>
#include <stdexcept>

#include "rANS/internal/EncoderBase.h"
#include "rANS/internal/Encoder.h"
#include "rANS/internal/EncoderSymbol.h"
#include "rANS/internal/helper.h"
#include "rANS/internal/SymbolTable.h"
#include "rANS/FrequencyTable.h"

namespace o2
{
namespace rans
{

template <typename coder_T, typename stream_T, typename source_T>
class Encoder : public internal::EncoderBase<coder_T, stream_T, source_T>
{

 public:
  //inherit constructors;
  using internal::EncoderBase<coder_T, stream_T, source_T>::EncoderBase;

  template <typename stream_IT, typename source_IT, std::enable_if_t<internal::isCompatibleIter_v<source_T, source_IT>, bool> = true>
  const stream_IT process(source_IT inputBegin, source_IT inputEnd, stream_IT outputBegin) const;

 private:
  using ransCoder_t = typename internal::EncoderBase<coder_T, stream_T, source_T>::ransCoder_t;
};

template <typename coder_T, typename stream_T, typename source_T>
template <typename stream_IT, typename source_IT, std::enable_if_t<internal::isCompatibleIter_v<source_T, source_IT>, bool>>
const stream_IT Encoder<coder_T, stream_T, source_T>::process(source_IT inputBegin, source_IT inputEnd, stream_IT outputBegin) const
{
  using namespace internal;
  LOG(trace) << "start encoding";
  RANSTimer t;
  t.start();

  if (inputBegin == inputEnd) {
    LOG(warning) << "passed empty message to encoder, skip encoding";
    return outputBegin;
  }

  ransCoder_t rans0{this->mSymbolTablePrecission};
  ransCoder_t rans1{this->mSymbolTablePrecission};

  stream_IT outputIter = outputBegin;
  source_IT inputIT = inputEnd;

  const auto inputBufferSize = std::distance(inputBegin, inputEnd);

  auto encode = [this](source_IT symbolIter, stream_IT outputIter, ransCoder_t& coder) {
    const source_T symbol = *symbolIter;
    const auto& encoderSymbol = (this->mSymbolTable)[symbol];
    return coder.putSymbol(outputIter, encoderSymbol);
  };

  // odd number of bytes?
  if (inputBufferSize & 1) {
    outputIter = encode(--inputIT, outputIter, rans0);
  }

  while (inputIT != inputBegin) { // NB: working in reverse!
    outputIter = encode(--inputIT, outputIter, rans1);
    outputIter = encode(--inputIT, outputIter, rans0);
  }
  outputIter = rans1.flush(outputIter);
  outputIter = rans0.flush(outputIter);
  // first iterator past the range so that sizes, distances and iterators work correctly.
  ++outputIter;

  t.stop();
  LOG(debug1) << "Encoder::" << __func__ << " {ProcessedBytes: " << inputBufferSize * sizeof(source_T) << ","
              << " inclusiveTimeMS: " << t.getDurationMS() << ","
              << " BandwidthMiBPS: " << std::fixed << std::setprecision(2) << (inputBufferSize * sizeof(source_T) * 1.0) / (t.getDurationS() * 1.0 * (1 << 20)) << "}";

// advanced diagnostics for debug builds
#if !defined(NDEBUG)

  const auto inputBufferSizeB = inputBufferSize * sizeof(source_T);

  LOG(debug2) << "EncoderProperties: {"
              << "sourceTypeB: " << sizeof(source_T) << ", "
              << "streamTypeB: " << sizeof(stream_T) << ", "
              << "coderTypeB: " << sizeof(coder_T) << ", "
              << "probabilityBits: " << this->mSymbolTablePrecission << ", "
              << "inputBufferSizeB: " << inputBufferSizeB << "}";
#endif

  LOG(trace) << "done encoding";

  return outputIter;
};

} // namespace rans
} // namespace o2

#endif /* RANS_ENCODER_H */