/*
 *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include "modules/rtp_rtcp/source/rtp_format_vp8.h"

#include <string.h>  // memcpy

#include <cassert>   // assert

namespace webrtc {

// Define how the VP8PacketizerModes are implemented.
// Modes are: kStrict, kAggregate, kSloppy.
const RtpFormatVp8::AggregationMode RtpFormatVp8::aggr_modes_[kNumModes] =
    { kAggrNone, kAggrPartitions, kAggrFragments };
const bool RtpFormatVp8::balance_modes_[kNumModes] =
    { true, true, false };
const bool RtpFormatVp8::separate_first_modes_[kNumModes] =
    { true, false, false };

RtpFormatVp8::RtpFormatVp8(const WebRtc_UWord8* payload_data,
                           WebRtc_UWord32 payload_size,
                           const RTPVideoHeaderVP8& hdr_info,
                           const RTPFragmentationHeader& fragmentation,
                           VP8PacketizerMode mode)
    : payload_data_(payload_data),
      payload_size_(static_cast<int>(payload_size)),
      payload_bytes_sent_(0),
      part_ix_(0),
      beginning_(true),
      first_fragment_(true),
      vp8_fixed_payload_descriptor_bytes_(1),
      aggr_mode_(aggr_modes_[mode]),
      balance_(balance_modes_[mode]),
      separate_first_(separate_first_modes_[mode]),
      hdr_info_(hdr_info),
      first_partition_in_packet_(0) {
  part_info_ = fragmentation;
}

RtpFormatVp8::RtpFormatVp8(const WebRtc_UWord8* payload_data,
                           WebRtc_UWord32 payload_size,
                           const RTPVideoHeaderVP8& hdr_info)
    : payload_data_(payload_data),
      payload_size_(static_cast<int>(payload_size)),
      part_info_(),
      payload_bytes_sent_(0),
      part_ix_(0),
      beginning_(true),
      first_fragment_(true),
      vp8_fixed_payload_descriptor_bytes_(1),
      aggr_mode_(aggr_modes_[kSloppy]),
      balance_(balance_modes_[kSloppy]),
      separate_first_(separate_first_modes_[kSloppy]),
      hdr_info_(hdr_info),
      first_partition_in_packet_(0) {
    part_info_.VerifyAndAllocateFragmentationHeader(1);
    part_info_.fragmentationLength[0] = payload_size;
    part_info_.fragmentationOffset[0] = 0;
}

int RtpFormatVp8::CalcNextSize(int max_payload_len, int remaining_bytes,
                               bool split_payload) const {
  if (max_payload_len == 0 || remaining_bytes == 0) {
    return 0;
  }
  if (!split_payload) {
    return max_payload_len >= remaining_bytes ? remaining_bytes : 0;
  }

  if (balance_) {
    // Balance payload sizes to produce (almost) equal size
    // fragments.
    // Number of fragments for remaining_bytes:
    int num_frags = remaining_bytes / max_payload_len + 1;
    // Number of bytes in this fragment:
    return static_cast<int>(static_cast<double>(remaining_bytes)
                            / num_frags + 0.5);
  } else {
    return max_payload_len >= remaining_bytes ? remaining_bytes
        : max_payload_len;
  }
}

int RtpFormatVp8::NextPacket(int max_payload_len, WebRtc_UWord8* buffer,
                             int* bytes_to_send, bool* last_packet) {
  if (max_payload_len < vp8_fixed_payload_descriptor_bytes_
      + PayloadDescriptorExtraLength() + 1) {
    // The provided payload length is not long enough for the payload
    // descriptor and one payload byte. Return an error.
    return -1;
  }
  const int num_partitions = part_info_.fragmentationVectorSize;
  int send_bytes = 0;  // How much data to send in this packet.
  bool split_payload = true;  // Splitting of partitions is initially allowed.
  int remaining_in_partition = part_info_.fragmentationOffset[part_ix_] -
      payload_bytes_sent_ + part_info_.fragmentationLength[part_ix_] +
      PayloadDescriptorExtraLength();
  int rem_payload_len = max_payload_len - vp8_fixed_payload_descriptor_bytes_;
  first_partition_in_packet_ = part_ix_;
  if (first_partition_in_packet_ > 8) return -1;

  while (int next_size = CalcNextSize(rem_payload_len, remaining_in_partition,
                                      split_payload)) {
    send_bytes += next_size;
    rem_payload_len -= next_size;
    remaining_in_partition -= next_size;

    if (remaining_in_partition == 0 && !(beginning_ && separate_first_)) {
      // Advance to next partition?
      // Check that there are more partitions; verify that we are either
      // allowed to aggregate fragments, or that we are allowed to
      // aggregate intact partitions and that we started this packet
      // with an intact partition (indicated by first_fragment_ == true).
      if (part_ix_ + 1 < num_partitions &&
          ((aggr_mode_ == kAggrFragments) ||
              (aggr_mode_ == kAggrPartitions && first_fragment_))) {
        remaining_in_partition
        = part_info_.fragmentationLength[++part_ix_];
        // Disallow splitting unless kAggrFragments. In kAggrPartitions,
        // we can only aggregate intact partitions.
        split_payload = (aggr_mode_ == kAggrFragments);
      }
    } else if (balance_ && remaining_in_partition > 0) {
      break;
    }
  }
  if (remaining_in_partition == 0) {
    ++part_ix_;  // Advance to next partition.
  }

  send_bytes -= PayloadDescriptorExtraLength();  // Remove extra length again.
  assert(send_bytes > 0);
  // Write the payload header and the payload to buffer.
  *bytes_to_send = WriteHeaderAndPayload(send_bytes, buffer, max_payload_len);
  if (*bytes_to_send < 0) {
    return -1;
  }

  beginning_ = false;  // Next packet cannot be first packet in frame.
  // Next packet starts new fragment if this ended one.
  first_fragment_ = (remaining_in_partition == 0);
  *last_packet = (payload_bytes_sent_ >= payload_size_);
  assert(!*last_packet || (payload_bytes_sent_ == payload_size_));
  return first_partition_in_packet_;
}

int RtpFormatVp8::WriteHeaderAndPayload(int payload_bytes,
                                        WebRtc_UWord8* buffer,
                                        int buffer_length) {
  // Write the VP8 payload descriptor.
  //       0
  //       0 1 2 3 4 5 6 7 8
  //      +-+-+-+-+-+-+-+-+-+
  //      |X| |N|S| PART_ID |
  //      +-+-+-+-+-+-+-+-+-+
  // X:   |I|L|T|K|         | (mandatory if any of the below are used)
  //      +-+-+-+-+-+-+-+-+-+
  // I:   |PictureID (8/16b)| (optional)
  //      +-+-+-+-+-+-+-+-+-+
  // L:   |   TL0PIC_IDX    | (optional)
  //      +-+-+-+-+-+-+-+-+-+
  // T/K: |TID:Y|  KEYIDX   | (optional)
  //      +-+-+-+-+-+-+-+-+-+

  assert(payload_bytes > 0);
  assert(payload_bytes_sent_ + payload_bytes <= payload_size_);
  assert(vp8_fixed_payload_descriptor_bytes_ + PayloadDescriptorExtraLength()
         + payload_bytes <= buffer_length);

  buffer[0] = 0;
  if (XFieldPresent())        buffer[0] |= kXBit;
  if (hdr_info_.nonReference) buffer[0] |= kNBit;
  if (first_fragment_)        buffer[0] |= kSBit;
  buffer[0] |= (first_partition_in_packet_ & kPartIdField);

  const int extension_length = WriteExtensionFields(buffer, buffer_length);

  memcpy(&buffer[vp8_fixed_payload_descriptor_bytes_ + extension_length],
         &payload_data_[payload_bytes_sent_], payload_bytes);

  payload_bytes_sent_ += payload_bytes;

  // Return total length of written data.
  return payload_bytes + vp8_fixed_payload_descriptor_bytes_
      + extension_length;
}

int RtpFormatVp8::WriteExtensionFields(WebRtc_UWord8* buffer,
                                       int buffer_length) const {
  int extension_length = 0;
  if (XFieldPresent()) {
    WebRtc_UWord8* x_field = buffer + vp8_fixed_payload_descriptor_bytes_;
    *x_field = 0;
    extension_length = 1;  // One octet for the X field.
    if (PictureIdPresent()) {
      if (WritePictureIDFields(x_field, buffer, buffer_length,
                               &extension_length) < 0) {
        return -1;
      }
    }
    if (TL0PicIdxFieldPresent()) {
      if (WriteTl0PicIdxFields(x_field, buffer, buffer_length,
                               &extension_length) < 0) {
        return -1;
      }
    }
    if (TIDFieldPresent() || KeyIdxFieldPresent()) {
      if (WriteTIDAndKeyIdxFields(x_field, buffer, buffer_length,
                                  &extension_length) < 0) {
        return -1;
      }
    }
    assert(extension_length == PayloadDescriptorExtraLength());
  }
  return extension_length;
}

int RtpFormatVp8::WritePictureIDFields(WebRtc_UWord8* x_field,
                                       WebRtc_UWord8* buffer,
                                       int buffer_length,
                                       int* extension_length) const {
  *x_field |= kIBit;
  const int pic_id_length = WritePictureID(
      buffer + vp8_fixed_payload_descriptor_bytes_ + *extension_length,
      buffer_length - vp8_fixed_payload_descriptor_bytes_
      - *extension_length);
  if (pic_id_length < 0) return -1;
  *extension_length += pic_id_length;
  return 0;
}

int RtpFormatVp8::WritePictureID(WebRtc_UWord8* buffer,
                                 int buffer_length) const {
  const WebRtc_UWord16 pic_id =
      static_cast<WebRtc_UWord16> (hdr_info_.pictureId);
  int picture_id_len = PictureIdLength();
  if (picture_id_len > buffer_length) return -1;
  if (picture_id_len == 2) {
    buffer[0] = 0x80 | ((pic_id >> 8) & 0x7F);
    buffer[1] = pic_id & 0xFF;
  } else if (picture_id_len == 1) {
    buffer[0] = pic_id & 0x7F;
  }
  return picture_id_len;
}

int RtpFormatVp8::WriteTl0PicIdxFields(WebRtc_UWord8* x_field,
                                       WebRtc_UWord8* buffer,
                                       int buffer_length,
                                       int* extension_length) const {
  if (buffer_length < vp8_fixed_payload_descriptor_bytes_ + *extension_length
      + 1) {
    return -1;
  }
  *x_field |= kLBit;
  buffer[vp8_fixed_payload_descriptor_bytes_
         + *extension_length] = hdr_info_.tl0PicIdx;
  ++*extension_length;
  return 0;
}

int RtpFormatVp8::WriteTIDAndKeyIdxFields(WebRtc_UWord8* x_field,
                                          WebRtc_UWord8* buffer,
                                          int buffer_length,
                                          int* extension_length) const {
  if (buffer_length < vp8_fixed_payload_descriptor_bytes_ + *extension_length
      + 1) {
    return -1;
  }
  WebRtc_UWord8* data_field =
      &buffer[vp8_fixed_payload_descriptor_bytes_ + *extension_length];
  *data_field = 0;
  if (TIDFieldPresent()) {
    *x_field |= kTBit;
    assert(hdr_info_.temporalIdx >= 0 && hdr_info_.temporalIdx <= 3);
    *data_field |= hdr_info_.temporalIdx << 6;
    *data_field |= hdr_info_.layerSync ? kYBit : 0;
  }
  if (KeyIdxFieldPresent()) {
    *x_field |= kKBit;
    *data_field |= (hdr_info_.keyIdx & kKeyIdxField);
  }
  ++*extension_length;
  return 0;
}

int RtpFormatVp8::PayloadDescriptorExtraLength() const {
  int length_bytes = PictureIdLength();
  if (TL0PicIdxFieldPresent()) ++length_bytes;
  if (TIDFieldPresent() || KeyIdxFieldPresent()) ++length_bytes;
  if (length_bytes > 0) ++length_bytes;  // Include the extension field.
  return length_bytes;
}

int RtpFormatVp8::PictureIdLength() const {
  if (hdr_info_.pictureId == kNoPictureId) {
    return 0;
  }
  if (hdr_info_.pictureId <= 0x7F) {
    return 1;
  }
  return 2;
}

bool RtpFormatVp8::XFieldPresent() const {
  return (TIDFieldPresent() || TL0PicIdxFieldPresent() || PictureIdPresent()
      || KeyIdxFieldPresent());
}

bool RtpFormatVp8::TIDFieldPresent() const {
  assert((hdr_info_.layerSync == false) ||
         (hdr_info_.temporalIdx != kNoTemporalIdx));
  return (hdr_info_.temporalIdx != kNoTemporalIdx);
}

bool RtpFormatVp8::KeyIdxFieldPresent() const {
  return (hdr_info_.keyIdx != kNoKeyIdx);
}

bool RtpFormatVp8::TL0PicIdxFieldPresent() const {
  return (hdr_info_.tl0PicIdx != kNoTl0PicIdx);
}
}  // namespace webrtc