/*

 * Copyright (c) 2026, Alliance for Open Media. All rights reserved.

 *

 * This source code is subject to the terms of the BSD 2 Clause License and

 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License

 * was not distributed with this source code in the LICENSE file, you can

 * obtain it at www.aomedia.org/license/software. If the Alliance for Open

 * Media Patent License 1.0 was not distributed with this source code in the

 * PATENTS file, you can obtain it at www.aomedia.org/license/patent.

 */

/*

 * See build_av1_enc_fuzzer.sh for building instructions.

 */

#include <stddef.h>

#include <stdint.h>

#include <stdlib.h>

#include <string.h>

#include "aom/aom_encoder.h"

#include "aom/aom_image.h"

#include "aom/aomcx.h"

namespace {

constexpr unsigned int kMaxDimension = 1024;

constexpr size_t kMinHeaderSize = 16;

// Bit masks derived from the mode_flags byte. The low two bits are used to

// select the encoding usage (see PickUsage).

enum ModeFlag {

  kLossless = 1u << 2,

  kRowMt = 1u << 3,

  kUseSecondResolution = 1u << 4,

  kKeyFrameSecond = 1u << 5,

  kErrorResilient = 1u << 6,

};

// Number of frames to encode for a given cpu_used value. Lower cpu_used

// values encode more slowly, so fewer frames are used to stay within the

// fuzzer's execution time budget (libFuzzer defaults to one second per

// input). This can be refined based on measured fuzzer performance.

constexpr unsigned int kNumFramesForCpuUsed[12] = {

  50,  // cpu_used 0

  50,  // cpu_used 1

  50,  // cpu_used 2

  60,  // cpu_used 3

  60,  // cpu_used 4

  70,  // cpu_used 5

  70,  // cpu_used 6

  80,  // cpu_used 7

  80,  // cpu_used 8

  90,  // cpu_used 9

  90,  // cpu_used 10

  100  // cpu_used 11

};

struct FuzzReader {

  const uint8_t *data;

  size_t size;

};

uint8_t ReadU8(FuzzReader *reader) {

  if (reader->size == 0) return 0;

  const uint8_t value = *reader->data++;

  --reader->size;

  return value;

}

uint16_t ReadU16(FuzzReader *reader) {

  if (reader->size < 2) return 0;

  const uint16_t value = reader->data[0] | (reader->data[1] << 8);

  reader->data += 2;

  reader->size -= 2;

  return value;

}

unsigned int UsageToIndex(unsigned int usage) {

  switch (usage) {

    case AOM_USAGE_GOOD_QUALITY: return 0;

    case AOM_USAGE_REALTIME: return 1;

    case AOM_USAGE_ALL_INTRA: return 2;

    default: return 0;

  }

}

unsigned int PickUsage(uint8_t raw) {

  switch (raw % 3) {

    case 0: return AOM_USAGE_GOOD_QUALITY;

    case 1: return AOM_USAGE_REALTIME;

    default: return AOM_USAGE_ALL_INTRA;

  }

}

aom_rc_mode PickRcMode(uint8_t raw) {

  switch (raw % 4) {

    case 0: return AOM_VBR;

    case 1: return AOM_CBR;

    case 2: return AOM_CQ;

    default: return AOM_Q;

  }

}

unsigned int PickDimension(uint16_t raw) { return 1u + (raw % kMaxDimension); }

int PickCpuUsed(unsigned int usage, uint8_t raw) {

  const int max_cpu_used = usage == AOM_USAGE_REALTIME ? 11 : 9;

  return raw % (max_cpu_used + 1);

}

bool DrainPackets(aom_codec_ctx_t *codec) {

  bool got_data = false;

  aom_codec_iter_t iter = nullptr;

  while (aom_codec_get_cx_data(codec, &iter) != nullptr) {

    got_data = true;

  }

  return got_data;

}

bool InitDefaultConfig(aom_codec_iface_t *iface, unsigned int usage,

                       aom_codec_enc_cfg_t *cfg) {

  const unsigned int usages[3] = { AOM_USAGE_GOOD_QUALITY, AOM_USAGE_REALTIME,

                                   AOM_USAGE_ALL_INTRA };

  const unsigned int requested_index = UsageToIndex(usage);

  for (unsigned int i = 0; i < 3; ++i) {

    const unsigned int index = (requested_index + i) % 3;

    if (aom_codec_enc_config_default(iface, cfg, usages[index]) ==

        AOM_CODEC_OK) {

      return true;

    }

  }

  return false;

}

// Deterministic PRNG so that the frame content is derived from the fuzzer

// input without requiring the reader to supply a full plane-sized chunk of

// data for every frame.

uint32_t Rand(uint32_t *state) {

  *state = *state * 1664525u + 1013904223u;

  return *state;

}

void FillPlane(uint8_t *plane, int stride, unsigned int width,

               unsigned int height, uint32_t *state) {

  for (unsigned int row = 0; row < height; ++row) {

    for (unsigned int col = 0; col < width; ++col) {

      plane[static_cast<size_t>(row) * stride + col] =

          static_cast<uint8_t>(Rand(state) >> 24);

    }

  }

}

bool BuildImage(FuzzReader *reader, unsigned int width, unsigned int height,

                aom_image_t *image, unsigned int frame_index) {

  if (aom_img_alloc(image, AOM_IMG_FMT_I420, width, height, 1) == nullptr) {

    return false;

  }

  // Seed a deterministic PRNG from the fuzzer input and the frame index so

  // that each encoded frame differs without consuming a plane-sized chunk of

  // input per frame.

  uint32_t state = 0;

  for (unsigned int i = 0; i < 4; ++i) {

    state = (state << 8) | ReadU8(reader);

  }

  const uint32_t golden_ratio = 0x9e3779b9u;

  state ^= frame_index * golden_ratio;

  const unsigned int uv_width = (width + 1) / 2;

  const unsigned int uv_height = (height + 1) / 2;

  FillPlane(image->planes[AOM_PLANE_Y], image->stride[AOM_PLANE_Y], width,

            height, &state);

  FillPlane(image->planes[AOM_PLANE_U], image->stride[AOM_PLANE_U], uv_width,

            uv_height, &state);

  FillPlane(image->planes[AOM_PLANE_V], image->stride[AOM_PLANE_V], uv_width,

            uv_height, &state);

  return true;

}

void ApplyControls(aom_codec_ctx_t *codec, unsigned int usage,

                   uint8_t mode_flags, uint8_t cpu_used_raw, uint8_t ctl0,

                   uint8_t ctl1) {

  const int cpu_used = PickCpuUsed(usage, cpu_used_raw);

  const unsigned int lossless = (mode_flags & kLossless) != 0;

  const unsigned int row_mt = (mode_flags & kRowMt) != 0;

  const unsigned int aq_mode = ctl0 % 4;

  const unsigned int deltaq_mode = ctl1 % 4;

  const unsigned int tile_columns = (ctl0 >> 4) & 0x3;

  const unsigned int tile_rows = (ctl1 >> 4) & 0x3;

  const unsigned int enable_cdef = (ctl0 >> 2) & 1;

  const unsigned int enable_restoration = (ctl1 >> 2) & 1;

  (void)AOM_CODEC_CONTROL_TYPECHECKED(codec, AOME_SET_CPUUSED, cpu_used);

  (void)AOM_CODEC_CONTROL_TYPECHECKED(codec, AV1E_SET_LOSSLESS, lossless);

  (void)AOM_CODEC_CONTROL_TYPECHECKED(codec, AV1E_SET_ROW_MT, row_mt);

  (void)AOM_CODEC_CONTROL_TYPECHECKED(codec, AV1E_SET_AQ_MODE, aq_mode);

  (void)AOM_CODEC_CONTROL_TYPECHECKED(codec, AV1E_SET_DELTAQ_MODE, deltaq_mode);

  (void)AOM_CODEC_CONTROL_TYPECHECKED(codec, AV1E_SET_TILE_COLUMNS,

                                      tile_columns);

  (void)AOM_CODEC_CONTROL_TYPECHECKED(codec, AV1E_SET_TILE_ROWS, tile_rows);

  (void)AOM_CODEC_CONTROL_TYPECHECKED(codec, AV1E_SET_ENABLE_CDEF, enable_cdef);

  (void)AOM_CODEC_CONTROL_TYPECHECKED(codec, AV1E_SET_ENABLE_RESTORATION,

                                      enable_restoration);

}

bool EncodeFrame(aom_codec_ctx_t *codec, FuzzReader *reader, unsigned int width,

                 unsigned int height, aom_codec_pts_t pts,

                 aom_enc_frame_flags_t flags) {

  aom_image_t image;

  memset(&image, 0, sizeof(image));

  if (!BuildImage(reader, width, height, &image, pts)) {

    return false;

  }

  const aom_codec_err_t enc_ret =

      aom_codec_encode(codec, &image, pts, 1, flags);

  if (enc_ret == AOM_CODEC_OK) {

    (void)DrainPackets(codec);

  }

  aom_img_free(&image);

  return true;

}

}  // namespace

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {

  aom_codec_iface_t *iface = aom_codec_av1_cx();

  if (iface == nullptr || size < kMinHeaderSize) return 0;

  FuzzReader reader = { data, size };

  const uint8_t mode_flags = ReadU8(&reader);

  const uint8_t cpu_used_raw = ReadU8(&reader);

  const uint8_t ctl0 = ReadU8(&reader);

  const uint8_t ctl1 = ReadU8(&reader);

  const unsigned int usage = PickUsage(mode_flags);

  const unsigned int width0 = PickDimension(ReadU16(&reader));

  const unsigned int height0 = PickDimension(ReadU16(&reader));

  const unsigned int bitrate = 1u + (ReadU16(&reader) % 4000u);

  const unsigned int width1 = PickDimension(ReadU16(&reader));

  const unsigned int height1 = PickDimension(ReadU16(&reader));

  const unsigned int threads0 = ReadU8(&reader) % 9;

  const unsigned int threads1 = ReadU8(&reader) % 9;

  aom_codec_enc_cfg_t cfg;

  if (!InitDefaultConfig(iface, usage, &cfg)) return 0;

  cfg.g_usage = usage;

  cfg.g_w = width0;

  cfg.g_h = height0;

  cfg.g_threads = threads0;

  cfg.g_forced_max_frame_width = kMaxDimension;

  cfg.g_forced_max_frame_height = kMaxDimension;

  cfg.g_timebase.num = 1;

  cfg.g_timebase.den = 1000000;

  cfg.g_pass = AOM_RC_ONE_PASS;

  cfg.g_lag_in_frames = 0;

  cfg.g_error_resilient =

      (mode_flags & kErrorResilient) ? AOM_ERROR_RESILIENT_DEFAULT : 0;

  cfg.rc_end_usage = PickRcMode(ctl0);

  cfg.rc_target_bitrate = bitrate;

  aom_codec_ctx_t codec;

  memset(&codec, 0, sizeof(codec));

  if (aom_codec_enc_init(&codec, iface, &cfg, 0) != AOM_CODEC_OK) return 0;

  const int cpu_used = PickCpuUsed(usage, cpu_used_raw);

  ApplyControls(&codec, usage, mode_flags, cpu_used_raw, ctl0, ctl1);

  const unsigned int num_frames = kNumFramesForCpuUsed[cpu_used];

  bool config_failed = false;

  for (unsigned int frame = 0; frame < num_frames; ++frame) {

    aom_enc_frame_flags_t flags = 0;

    if (frame == 1 && (mode_flags & kKeyFrameSecond)) {

      flags |= AOM_EFLAG_FORCE_KF;

    }

    unsigned int width = width0;

    unsigned int height = height0;

    if (mode_flags & kUseSecondResolution) {

      // Vary the switch frame based on the input so different encodings

      // exercise the resolution change at different points in the stream.

      // num_frames >= 50 for every cpu_used, so switch_frame and

      // restore_frame stay within [1, num_frames - 1].

      const unsigned int switch_frame = 1u + (ctl0 % (num_frames / 4u));

      const unsigned int restore_frame =

          switch_frame + 1u + (ctl1 % (num_frames / 4u));

      if (frame == switch_frame) {

        cfg.g_w = width1;

        cfg.g_h = height1;

        cfg.g_threads = threads1;

        cfg.rc_end_usage = PickRcMode(ctl1);

        if (aom_codec_enc_config_set(&codec, &cfg) != AOM_CODEC_OK) {

          config_failed = true;

          break;

        }

        width = width1;

        height = height1;

      } else if (frame == restore_frame) {

        cfg.g_w = width0;

        cfg.g_h = height0;

        cfg.g_threads = threads0;

        cfg.rc_end_usage = PickRcMode(ctl0);

        if (aom_codec_enc_config_set(&codec, &cfg) != AOM_CODEC_OK) {

          config_failed = true;

          break;

        }

        width = width0;

        height = height0;

      }

    }

    if (!EncodeFrame(&codec, &reader, width, height, frame, flags)) {

      config_failed = true;

      break;

    }

  }

  if (!config_failed) {

    while (aom_codec_encode(&codec, nullptr, 0, 0, 0) == AOM_CODEC_OK &&

           DrainPackets(&codec)) {

    }

  }

  (void)aom_codec_destroy(&codec);

  return 0;

}