/*-
 * Copyright 2003,2004 Colin Percival
 * All rights reserved
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted providing that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * Changelog:
 * 2009-03-31 - Change to use Streams.  Move CRC code to crc.{h,cc}
 *                --Stephen Adams <sra@chromium.org>
 * 2013-04-10 - Add wrapper method to apply a patch to files directly.
 *                --Joshua Pawlicki <waffles@chromium.org>
 */

// Copyright (c) 2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "courgette/third_party/bsdiff.h"

#include "base/files/memory_mapped_file.h"
#include "courgette/crc.h"
#include "courgette/streams.h"

namespace courgette {

BSDiffStatus MBS_ReadHeader(SourceStream* stream, MBSPatchHeader* header) {
  if (!stream->Read(header->tag, sizeof(header->tag))) return READ_ERROR;
  if (!stream->ReadVarint32(&header->slen)) return READ_ERROR;
  if (!stream->ReadVarint32(&header->scrc32)) return READ_ERROR;
  if (!stream->ReadVarint32(&header->dlen)) return READ_ERROR;

  // The string will have a NUL terminator that we don't use, hence '-1'.
  COMPILE_ASSERT(sizeof(MBS_PATCH_HEADER_TAG) - 1 == sizeof(header->tag),
                 MBS_PATCH_HEADER_TAG_must_match_header_field_size);
  if (memcmp(header->tag, MBS_PATCH_HEADER_TAG, 8) != 0)
    return UNEXPECTED_ERROR;

  return OK;
}

BSDiffStatus MBS_ApplyPatch(const MBSPatchHeader *header,
                            SourceStream* patch_stream,
                            const uint8* old_start, size_t old_size,
                            SinkStream* new_stream) {
  const uint8* old_end = old_start + old_size;

  SourceStreamSet patch_streams;
  if (!patch_streams.Init(patch_stream))
    return READ_ERROR;

  SourceStream* control_stream_copy_counts = patch_streams.stream(0);
  SourceStream* control_stream_extra_counts = patch_streams.stream(1);
  SourceStream* control_stream_seeks = patch_streams.stream(2);
  SourceStream* diff_skips = patch_streams.stream(3);
  SourceStream* diff_bytes = patch_streams.stream(4);
  SourceStream* extra_bytes = patch_streams.stream(5);

  const uint8* extra_start = extra_bytes->Buffer();
  const uint8* extra_end = extra_start + extra_bytes->Remaining();
  const uint8* extra_position = extra_start;

  const uint8* old_position = old_start;

  if (header->dlen && !new_stream->Reserve(header->dlen))
    return MEM_ERROR;

  uint32 pending_diff_zeros = 0;
  if (!diff_skips->ReadVarint32(&pending_diff_zeros))
    return UNEXPECTED_ERROR;

  while (!control_stream_copy_counts->Empty()) {
    uint32 copy_count, extra_count;
    int32 seek_adjustment;
    if (!control_stream_copy_counts->ReadVarint32(&copy_count))
      return UNEXPECTED_ERROR;
    if (!control_stream_extra_counts->ReadVarint32(&extra_count))
      return UNEXPECTED_ERROR;
    if (!control_stream_seeks->ReadVarint32Signed(&seek_adjustment))
      return UNEXPECTED_ERROR;

#ifdef DEBUG_bsmedberg
    printf("Applying block:  copy: %-8u extra: %-8u seek: %+i\n",
           copy_count, extra_count, seek_adjustment);
#endif
    // Byte-wise arithmetically add bytes from old file to bytes from the diff
    // block.
    if (copy_count > static_cast<size_t>(old_end - old_position))
      return UNEXPECTED_ERROR;

    // Add together bytes from the 'old' file and the 'diff' stream.
    for (size_t i = 0;  i < copy_count;  ++i) {
      uint8 diff_byte = 0;
      if (pending_diff_zeros) {
        --pending_diff_zeros;
      } else {
        if (!diff_skips->ReadVarint32(&pending_diff_zeros))
          return UNEXPECTED_ERROR;
        if (!diff_bytes->Read(&diff_byte, 1))
          return UNEXPECTED_ERROR;
      }
      uint8 byte = old_position[i] + diff_byte;
      if (!new_stream->Write(&byte, 1))
        return MEM_ERROR;
    }
    old_position += copy_count;

    // Copy bytes from the extra block.
    if (extra_count > static_cast<size_t>(extra_end - extra_position))
      return UNEXPECTED_ERROR;

    if (!new_stream->Write(extra_position, extra_count))
      return MEM_ERROR;

    extra_position += extra_count;

    // "seek" forwards (or backwards) in oldfile.
    if (old_position + seek_adjustment < old_start ||
        old_position + seek_adjustment > old_end)
      return UNEXPECTED_ERROR;

    old_position += seek_adjustment;
  }

  if (!control_stream_copy_counts->Empty() ||
      !control_stream_extra_counts->Empty() ||
      !control_stream_seeks->Empty() ||
      !diff_skips->Empty() ||
      !diff_bytes->Empty() ||
      !extra_bytes->Empty())
    return UNEXPECTED_ERROR;

  return OK;
}

BSDiffStatus ApplyBinaryPatch(SourceStream* old_stream,
                              SourceStream* patch_stream,
                              SinkStream* new_stream) {
  MBSPatchHeader header;
  BSDiffStatus ret = MBS_ReadHeader(patch_stream, &header);
  if (ret != OK) return ret;

  const uint8* old_start = old_stream->Buffer();
  size_t old_size = old_stream->Remaining();

  if (old_size != header.slen) return UNEXPECTED_ERROR;

  if (CalculateCrc(old_start, old_size) != header.scrc32)
    return CRC_ERROR;

  MBS_ApplyPatch(&header, patch_stream, old_start, old_size, new_stream);

  return OK;
}

BSDiffStatus ApplyBinaryPatch(const base::FilePath& old_file_path,
                              const base::FilePath& patch_file_path,
                              const base::FilePath& new_file_path) {
  // Set up the old stream.
  base::MemoryMappedFile old_file;
  if (!old_file.Initialize(old_file_path)) {
    return READ_ERROR;
  }
  SourceStream old_file_stream;
  old_file_stream.Init(old_file.data(), old_file.length());

  // Set up the patch stream.
  base::MemoryMappedFile patch_file;
  if (!patch_file.Initialize(patch_file_path)) {
    return READ_ERROR;
  }
  SourceStream patch_file_stream;
  patch_file_stream.Init(patch_file.data(), patch_file.length());

  // Set up the new stream and apply the patch.
  SinkStream new_sink_stream;
  BSDiffStatus status = ApplyBinaryPatch(&old_file_stream,
                                         &patch_file_stream,
                                         &new_sink_stream);
  if (status != OK) {
    return status;
  }

  // Write the stream to disk.
  int written = base::WriteFile(
      new_file_path,
      reinterpret_cast<const char*>(new_sink_stream.Buffer()),
      static_cast<int>(new_sink_stream.Length()));
  if (written != static_cast<int>(new_sink_stream.Length()))
    return WRITE_ERROR;
  return OK;
}

}  // namespace