#include "../src/meshoptimizer.h"

#include <stdint.h>

#include <stdlib.h>

#include <string.h>

void fuzzDecoder(const uint8_t* data, size_t size, size_t stride, int (*decode)(void*, size_t, size_t, const unsigned char*, size_t))

{

  size_t count = 66; // must be divisible by 3 for decodeIndexBuffer; should be >=64 to cover large vertex blocks

  void* destination = malloc(count * stride);

  assert(destination);

  int rc = decode(destination, count, stride, reinterpret_cast<const unsigned char*>(data), size);

  (void)rc;

  free(destination);

}

void fuzzRoundtrip(const uint8_t* data, size_t size, size_t stride, int level)

{

  size_t count = size / stride;

  size_t bound = meshopt_encodeVertexBufferBound(count, stride);

  void* encoded = malloc(bound);

  void* decoded = malloc(count * stride);

  assert(encoded && decoded);

  size_t res = meshopt_encodeVertexBufferLevel(static_cast<unsigned char*>(encoded), bound, data, count, stride, level, -1);

  assert(res > 0 && res <= bound);

  // encode again at the boundary to check for memory safety

  // this should produce the same output because encoder is deterministic

  size_t rese = meshopt_encodeVertexBufferLevel(static_cast<unsigned char*>(encoded) + bound - res, res, data, count, stride, level, -1);

  assert(rese == res);

  int rc = meshopt_decodeVertexBuffer(decoded, count, stride, static_cast<unsigned char*>(encoded) + bound - res, res);

  assert(rc == 0);

  assert(memcmp(data, decoded, count * stride) == 0);

  free(decoded);

  free(encoded);

}

size_t align(size_t value, size_t alignment)

{

  return (value + alignment - 1) & ~(alignment - 1);

}

void fuzzDecodeMeshlet(size_t vertex_count, size_t triangle_count, const unsigned char* data, size_t size)

{

  // raw decoding: allowed to write align(count, 4) elements

  unsigned int rt[256];

  unsigned int rv[256];

  meshopt_decodeMeshletRaw(rv + 256 - align(vertex_count, 4), vertex_count, rt + 256 - align(triangle_count, 4), triangle_count, data, size);

  // regular decoding: allowed to write align(count * size, 4) bytes

  // with variations for 3-byte triangles and 2-byte vertex references

  unsigned short rsv[256];

  unsigned char rbt[256 * 3];

  meshopt_decodeMeshlet(rv + 256 - vertex_count, vertex_count, 4, rt + 256 - triangle_count, triangle_count, 4, data, size);

  meshopt_decodeMeshlet(rsv + 256 - align(vertex_count, 2), vertex_count, 2, rt + 256 - triangle_count, triangle_count, 4, data, size);

  meshopt_decodeMeshlet(rv + 256 - vertex_count, vertex_count, 4, rbt + 256 * 3 - align(triangle_count * 3, 4), triangle_count, 3, data, size);

  meshopt_decodeMeshlet(rsv + 256 - align(vertex_count, 2), vertex_count, 2, rbt + 256 * 3 - align(triangle_count * 3, 4), triangle_count, 3, data, size);

}

void fuzzRoundtripMeshlet(const uint8_t* data, size_t size)

{

  size_t triangle_count = size / 3;

  if (triangle_count > 256)

    triangle_count = 256;

  unsigned char buf[4096];

  size_t enc = meshopt_encodeMeshlet(buf, sizeof(buf), NULL, 0, reinterpret_cast<const unsigned char*>(data), triangle_count);

  assert(enc > 0);

  assert(enc <= meshopt_encodeMeshletBound(0, triangle_count));

  unsigned int rt4[256];

  int rc4 = meshopt_decodeMeshlet(static_cast<unsigned int*>(NULL), 0, rt4, triangle_count, buf, enc);

  assert(rc4 == 0);

  for (size_t i = 0; i < triangle_count; ++i)

  {

    unsigned char a = data[i * 3 + 0], b = data[i * 3 + 1], c = data[i * 3 + 2];

    unsigned int abc = (a << 0) | (b << 8) | (c << 16);

    unsigned int bca = (b << 0) | (c << 8) | (a << 16);

    unsigned int cba = (c << 0) | (a << 8) | (b << 16);

    unsigned int tri = rt4[i];

    assert(tri == abc || tri == bca || tri == cba);

  }

  unsigned char rt3[256 * 3];

  int rc3 = meshopt_decodeMeshlet(static_cast<unsigned int*>(NULL), 0, rt3, triangle_count, buf, enc);

  assert(rc3 == 0);

  for (size_t i = 0; i < triangle_count; ++i)

  {

    unsigned char a = data[i * 3 + 0], b = data[i * 3 + 1], c = data[i * 3 + 2];

    unsigned int abc = (a << 0) | (b << 8) | (c << 16);

    unsigned int bca = (b << 0) | (c << 8) | (a << 16);

    unsigned int cba = (c << 0) | (a << 8) | (b << 16);

    unsigned int tri = rt3[i * 3 + 0] | (rt3[i * 3 + 1] << 8) | (rt3[i * 3 + 2] << 16);

    assert(tri == abc || tri == bca || tri == cba);

  }

}

void fuzzRoundtripMeshletV(const uint8_t* data, size_t size)

{

  size_t vertex_count = size / 4;

  if (vertex_count > 256)

    vertex_count = 256;

  unsigned char tri[4] = {0, 1, 2};

  unsigned char buf[4096];

  size_t enc = meshopt_encodeMeshlet(buf, sizeof(buf), reinterpret_cast<const uint32_t*>(data), vertex_count, tri, 1);

  assert(enc > 0);

  assert(enc <= meshopt_encodeMeshletBound(vertex_count, 1));

  unsigned int rv4[256];

  int rc4 = meshopt_decodeMeshlet(rv4, vertex_count, tri, 1, buf, enc);

  assert(rc4 == 0);

  for (size_t i = 0; i < vertex_count; ++i)

    assert(rv4[i] == reinterpret_cast<const uint32_t*>(data)[i]);

  unsigned short rv2[256];

  int rc2 = meshopt_decodeMeshlet(rv2, vertex_count, tri, 1, buf, enc);

  assert(rc2 == 0);

  for (size_t i = 0; i < vertex_count; ++i)

    assert(rv2[i] == uint16_t(reinterpret_cast<const uint32_t*>(data)[i]));

}

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

{

  // decodeIndexBuffer supports 2 and 4-byte indices

  fuzzDecoder(data, size, 2, meshopt_decodeIndexBuffer);

  fuzzDecoder(data, size, 4, meshopt_decodeIndexBuffer);

  // decodeIndexSequence supports 2 and 4-byte indices

  fuzzDecoder(data, size, 2, meshopt_decodeIndexSequence);

  fuzzDecoder(data, size, 4, meshopt_decodeIndexSequence);

  // decodeVertexBuffer supports any strides divisible by 4 in 4-256 interval

  // it's a waste of time to check all of them, so we'll just check a few with different alignment mod 16

  fuzzDecoder(data, size, 4, meshopt_decodeVertexBuffer);

  fuzzDecoder(data, size, 16, meshopt_decodeVertexBuffer);

  fuzzDecoder(data, size, 24, meshopt_decodeVertexBuffer);

  fuzzDecoder(data, size, 32, meshopt_decodeVertexBuffer);

  // encodeVertexBuffer/decodeVertexBuffer should roundtrip for any stride, check a few with different alignment mod 16

  // this also checks memory safety properties of the encoder

  // to conserve time, we only check one version/level combination, biased towards version 1

  uint8_t data0 = size > 0 ? data[0] : 0;

  int level = data0 % 5;

  meshopt_encodeVertexVersion(level < 4 ? 1 : 0);

  fuzzRoundtrip(data, size, 4, level);

  fuzzRoundtrip(data, size, 16, level);

  fuzzRoundtrip(data, size, 24, level);

  fuzzRoundtrip(data, size, 32, level);

  // validate that decodeMeshlet works on untrusted data and is memory safe within documented limits

  if (size > 2)

    fuzzDecodeMeshlet(data[0] + 1, data[1] + 1, reinterpret_cast<const unsigned char*>(data + 2), size - 2);

  // validate that index data roundtrips in meshlet encoding modulo rotation

  fuzzRoundtripMeshlet(data, size);

  // validate that vertex data roundtrips in meshlet encoding

  fuzzRoundtripMeshletV(data, size);

  return 0;

}