/*
 *  Copyright (c) 2021 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 <cstddef>
#include <cstdint>
#include <limits>
#include <span>

#include "api/video/video_layers_allocation.h"
#include "modules/rtp_rtcp/source/rtp_video_layers_allocation_extension.h"
#include "rtc_base/checks.h"
#include "test/fuzzers/fuzz_data_helper.h"

namespace webrtc {

void FuzzOneInput(FuzzDataHelper fuzz_data) {
  // Video layers allocation is an rtp header extension.
  // Per https://datatracker.ietf.org/doc/html/rfc8285#section-4.3
  // rtp header extension uses up to one byte to store the size, i.e.
  // maximum size of any rtp header extension is 255 bytes.
  constexpr int kMaxSize = std::numeric_limits<uint8_t>::max();
  if (fuzz_data.size() > kMaxSize) {
    return;
  }
  std::span<const uint8_t> raw = fuzz_data.ReadRemaining();

  VideoLayersAllocation allocation1;
  if (!RtpVideoLayersAllocationExtension::Parse(raw, &allocation1)) {
    // Ignore invalid buffer and move on.
    return;
  }

  // Write parsed allocation back into raw buffer.
  size_t value_size = RtpVideoLayersAllocationExtension::ValueSize(allocation1);
  // Check `writer` use minimal number of bytes to pack the extension by
  // checking it doesn't use more than reader consumed.
  RTC_CHECK_LE(value_size, raw.size());
  uint8_t some_memory[kMaxSize];
  RTC_CHECK_LE(value_size, kMaxSize);
  std::span<uint8_t> write_buffer(some_memory, value_size);
  RTC_CHECK(
      RtpVideoLayersAllocationExtension::Write(write_buffer, allocation1));

  // Parse what Write assembled.
  // Unlike random input that should always succeed.
  VideoLayersAllocation allocation2;
  RTC_CHECK(
      RtpVideoLayersAllocationExtension::Parse(write_buffer, &allocation2));

  RTC_CHECK_EQ(allocation1.rtp_stream_index, allocation2.rtp_stream_index);
  RTC_CHECK_EQ(allocation1.resolution_and_frame_rate_is_valid,
               allocation2.resolution_and_frame_rate_is_valid);
  RTC_CHECK_EQ(allocation1.active_spatial_layers.size(),
               allocation2.active_spatial_layers.size());
  RTC_CHECK(allocation1 == allocation2);
}

}  // namespace webrtc