/*
 *  Copyright (c) 2016 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 <cstdint>
#include <vector>

#include "common_video/h264/h264_common.h"
#include "common_video/h264/sps_vui_rewriter.h"
#include "rtc_base/bit_buffer.h"
#include "rtc_base/buffer.h"
#include "rtc_base/logging.h"
#include "test/gtest.h"

namespace webrtc {

enum SpsMode {
  kNoRewriteRequired_VuiOptimal,
  kRewriteRequired_NoVui,
  kRewriteRequired_NoBitstreamRestriction,
  kRewriteRequired_VuiSuboptimal,
};

static const size_t kSpsBufferMaxSize = 256;
static const size_t kWidth = 640;
static const size_t kHeight = 480;

// Generates a fake SPS with basically everything empty and with characteristics
// based off SpsMode.
// Pass in a buffer of at least kSpsBufferMaxSize.
// The fake SPS that this generates also always has at least one emulation byte
// at offset 2, since the first two bytes are always 0, and has a 0x3 as the
// level_idc, to make sure the parser doesn't eat all 0x3 bytes.
void GenerateFakeSps(SpsMode mode, rtc::Buffer* out_buffer) {
  uint8_t rbsp[kSpsBufferMaxSize] = {0};
  rtc::BitBufferWriter writer(rbsp, kSpsBufferMaxSize);
  // Profile byte.
  writer.WriteUInt8(0);
  // Constraint sets and reserved zero bits.
  writer.WriteUInt8(0);
  // level_idc.
  writer.WriteUInt8(3);
  // seq_paramter_set_id.
  writer.WriteExponentialGolomb(0);
  // Profile is not special, so we skip all the chroma format settings.

  // Now some bit magic.
  // log2_max_frame_num_minus4: ue(v). 0 is fine.
  writer.WriteExponentialGolomb(0);
  // pic_order_cnt_type: ue(v).
  writer.WriteExponentialGolomb(0);
  // log2_max_pic_order_cnt_lsb_minus4: ue(v). 0 is fine.
  writer.WriteExponentialGolomb(0);

  // max_num_ref_frames: ue(v). Use 1, to make optimal/suboptimal more obvious.
  writer.WriteExponentialGolomb(1);
  // gaps_in_frame_num_value_allowed_flag: u(1).
  writer.WriteBits(0, 1);
  // Next are width/height. First, calculate the mbs/map_units versions.
  uint16_t width_in_mbs_minus1 = (kWidth + 15) / 16 - 1;

  // For the height, we're going to define frame_mbs_only_flag, so we need to
  // divide by 2. See the parser for the full calculation.
  uint16_t height_in_map_units_minus1 = ((kHeight + 15) / 16 - 1) / 2;
  // Write each as ue(v).
  writer.WriteExponentialGolomb(width_in_mbs_minus1);
  writer.WriteExponentialGolomb(height_in_map_units_minus1);
  // frame_mbs_only_flag: u(1). Needs to be false.
  writer.WriteBits(0, 1);
  // mb_adaptive_frame_field_flag: u(1).
  writer.WriteBits(0, 1);
  // direct_8x8_inferene_flag: u(1).
  writer.WriteBits(0, 1);
  // frame_cropping_flag: u(1). 1, so we can supply crop.
  writer.WriteBits(1, 1);
  // Now we write the left/right/top/bottom crop. For simplicity, we'll put all
  // the crop at the left/top.
  // We picked a 4:2:0 format, so the crops are 1/2 the pixel crop values.
  // Left/right.
  writer.WriteExponentialGolomb(((16 - (kWidth % 16)) % 16) / 2);
  writer.WriteExponentialGolomb(0);
  // Top/bottom.
  writer.WriteExponentialGolomb(((16 - (kHeight % 16)) % 16) / 2);
  writer.WriteExponentialGolomb(0);

  // Finally! The VUI.
  // vui_parameters_present_flag: u(1)
  if (mode == kRewriteRequired_NoVui) {
    writer.WriteBits(0, 1);
  } else {
    writer.WriteBits(1, 1);
    // VUI time. 8 flags to ignore followed by the bitstream restriction flag.
    writer.WriteBits(0, 8);
    if (mode == kRewriteRequired_NoBitstreamRestriction) {
      writer.WriteBits(0, 1);
    } else {
      writer.WriteBits(1, 1);
      // Write some defaults. Shouldn't matter for parsing, though.
      // motion_vectors_over_pic_boundaries_flag: u(1)
      writer.WriteBits(1, 1);
      // max_bytes_per_pic_denom: ue(v)
      writer.WriteExponentialGolomb(2);
      // max_bits_per_mb_denom: ue(v)
      writer.WriteExponentialGolomb(1);
      // log2_max_mv_length_horizontal: ue(v)
      // log2_max_mv_length_vertical: ue(v)
      writer.WriteExponentialGolomb(16);
      writer.WriteExponentialGolomb(16);

      // Next are the limits we care about.
      // max_num_reorder_frames: ue(v)
      // max_dec_frame_buffering: ue(v)
      if (mode == kRewriteRequired_VuiSuboptimal) {
        writer.WriteExponentialGolomb(4);
        writer.WriteExponentialGolomb(4);
      } else {
        writer.WriteExponentialGolomb(0);
        writer.WriteExponentialGolomb(1);
      }
    }
  }

  // Get the number of bytes written (including the last partial byte).
  size_t byte_count, bit_offset;
  writer.GetCurrentOffset(&byte_count, &bit_offset);
  if (bit_offset > 0) {
    byte_count++;
  }

  H264::WriteRbsp(rbsp, byte_count, out_buffer);
}

void TestSps(SpsMode mode, SpsVuiRewriter::ParseResult expected_parse_result) {
  rtc::LogMessage::LogToDebug(rtc::LS_VERBOSE);
  rtc::Buffer original_sps;
  GenerateFakeSps(mode, &original_sps);

  absl::optional<SpsParser::SpsState> sps;
  rtc::Buffer rewritten_sps;
  SpsVuiRewriter::ParseResult result = SpsVuiRewriter::ParseAndRewriteSps(
      original_sps.data(), original_sps.size(), &sps, &rewritten_sps);
  EXPECT_EQ(expected_parse_result, result);
  ASSERT_TRUE(sps);
  EXPECT_EQ(sps->width, kWidth);
  EXPECT_EQ(sps->height, kHeight);
  if (mode != kRewriteRequired_NoVui) {
    EXPECT_EQ(sps->vui_params_present, 1u);
  }

  if (result == SpsVuiRewriter::ParseResult::kVuiRewritten) {
    // Ensure that added/rewritten SPS is parsable.
    rtc::Buffer tmp;
    result = SpsVuiRewriter::ParseAndRewriteSps(
        rewritten_sps.data(), rewritten_sps.size(), &sps, &tmp);
    EXPECT_EQ(SpsVuiRewriter::ParseResult::kVuiOk, result);
    ASSERT_TRUE(sps);
    EXPECT_EQ(sps->width, kWidth);
    EXPECT_EQ(sps->height, kHeight);
    EXPECT_EQ(sps->vui_params_present, 1u);
  }
}

#define REWRITE_TEST(test_name, mode, expected_parse_result) \
  TEST(SpsVuiRewriterTest, test_name) { TestSps(mode, expected_parse_result); }

REWRITE_TEST(VuiAlreadyOptimal,
             kNoRewriteRequired_VuiOptimal,
             SpsVuiRewriter::ParseResult::kVuiOk);
REWRITE_TEST(RewriteFullVui,
             kRewriteRequired_NoVui,
             SpsVuiRewriter::ParseResult::kVuiRewritten);
REWRITE_TEST(AddBitstreamRestriction,
             kRewriteRequired_NoBitstreamRestriction,
             SpsVuiRewriter::ParseResult::kVuiRewritten);
REWRITE_TEST(RewriteSuboptimalVui,
             kRewriteRequired_VuiSuboptimal,
             SpsVuiRewriter::ParseResult::kVuiRewritten);
}  // namespace webrtc