#include "shared/Scene/VtxData.h"

#include <algorithm>
#include <assert.h>
#include <stdio.h>

bool isMeshDataValid(const char* fileName)
{
  FILE* f = fopen(fileName, "rb");

  if (!f)
    return false;

  SCOPE_EXIT
  {
    fclose(f);
  };

  MeshFileHeader header;

  if (fread(&header, 1, sizeof(header), f) != sizeof(header))
    return false;

  if (fseek(f, sizeof(Mesh) * header.meshCount, SEEK_CUR))
    return false;

  if (fseek(f, sizeof(BoundingBox) * header.meshCount, SEEK_CUR))
    return false;

  if (fseek(f, header.indexDataSize, SEEK_CUR))
    return false;

  if (fseek(f, header.vertexDataSize, SEEK_CUR))
    return false;

  return true;
}

bool isMeshHierarchyValid(const char* fileName)
{
  FILE* f = fopen(fileName, "rb");

  if (!f)
    return false;

  SCOPE_EXIT
  {
    fclose(f);
  };

  return true;
}

bool isMeshMaterialsValid(const char* fileName)
{
  FILE* f = fopen(fileName, "rb");

  if (!f)
    return false;

  SCOPE_EXIT
  {
    fclose(f);
  };

  uint64_t numMaterials  = 0;
  uint64_t materialsSize = 0;

  if (fread(&numMaterials, 1, sizeof(numMaterials), f) != sizeof(numMaterials))
    return false;
  if (fread(&materialsSize, 1, sizeof(materialsSize), f) != sizeof(materialsSize))
    return false;
  if (numMaterials * sizeof(Material) != materialsSize)
    return false;

  return true;
}

MeshFileHeader loadMeshData(const char* meshFile, MeshData& out)
{
  FILE* f = fopen(meshFile, "rb");

  assert(f);

  if (!f) {
    printf("Cannot open '%s'.\n", meshFile);
    assert(false);
    exit(EXIT_FAILURE);
  }

  SCOPE_EXIT
  {
    fclose(f);
  };

  MeshFileHeader header;

  if (fread(&header, 1, sizeof(header), f) != sizeof(header)) {
    printf("Unable to read mesh file header.\n");
    assert(false);
    exit(EXIT_FAILURE);
  }

  if (fread(&out.streams, 1, sizeof(out.streams), f) != sizeof(out.streams)) {
    printf("Unable to read vertex streams description.\n");
    assert(false);
    exit(EXIT_FAILURE);
  }

  out.meshes.resize(header.meshCount);
  if (fread(out.meshes.data(), sizeof(Mesh), header.meshCount, f) != header.meshCount) {
    printf("Could not read mesh descriptors.\n");
    assert(false);
    exit(EXIT_FAILURE);
  }
  out.boxes.resize(header.meshCount);
  if (fread(out.boxes.data(), sizeof(BoundingBox), header.meshCount, f) != header.meshCount) {
    printf("Could not read bounding boxes.\n");
    assert(false);
    exit(EXIT_FAILURE);
  }

  out.indexData.resize(header.indexDataSize / sizeof(uint32_t));
  out.vertexData.resize(header.vertexDataSize);

  if (fread(out.indexData.data(), 1, header.indexDataSize, f) != header.indexDataSize) {
    printf("Unable to read index data.\n");
    assert(false);
    exit(EXIT_FAILURE);
  }

  if (fread(out.vertexData.data(), 1, header.vertexDataSize, f) != header.vertexDataSize) {
    printf("Unable to read vertex data.\n");
    assert(false);
    exit(EXIT_FAILURE);
  }

  return header;
}

void loadMeshDataMaterials(const char* fileName, MeshData& out)
{
  FILE* f = fopen(fileName, "rb");

  if (!f) {
    printf("Cannot open '%s'.\n", fileName);
    assert(false);
    exit(EXIT_FAILURE);
  }

  uint64_t numMaterials  = 0;
  uint64_t materialsSize = 0;

  if (fread(&numMaterials, 1, sizeof(numMaterials), f) != sizeof(numMaterials)) {
    printf("Unable to read numMaterials.\n");
    assert(false);
    exit(EXIT_FAILURE);
  }
  if (fread(&materialsSize, 1, sizeof(materialsSize), f) != sizeof(materialsSize)) {
    printf("Unable to read materialsSize.\n");
    assert(false);
    exit(EXIT_FAILURE);
  }

  if (numMaterials * sizeof(Material) != materialsSize) {
    printf("Corrupted material file '%s'.\n", fileName);
    assert(false);
    exit(EXIT_FAILURE);
  }

  out.materials.resize(numMaterials);
  if (fread(out.materials.data(), 1, materialsSize, f) != materialsSize) {
    printf("Unable to read material data.\n");
    assert(false);
    exit(EXIT_FAILURE);
  }

  loadStringList(f, out.textureFiles);

  fclose(f);
}

void saveMeshData(const char* fileName, const MeshData& m)
{
  FILE* f = fopen(fileName, "wb");

  if (!f) {
    printf("Error opening file '%s' for writing.\n", fileName);
    assert(false);
    exit(EXIT_FAILURE);
  }

  const MeshFileHeader header = {
    .meshCount      = (uint32_t)m.meshes.size(),
    .indexDataSize  = (uint32_t)(m.indexData.size() * sizeof(uint32_t)),
    .vertexDataSize = (uint32_t)(m.vertexData.size()),
  };

  fwrite(&header, 1, sizeof(header), f);
  fwrite(&m.streams, 1, sizeof(m.streams), f);
  fwrite(m.meshes.data(), sizeof(Mesh), header.meshCount, f);
  fwrite(m.boxes.data(), sizeof(BoundingBox), header.meshCount, f);
  fwrite(m.indexData.data(), 1, header.indexDataSize, f);
  fwrite(m.vertexData.data(), 1, header.vertexDataSize, f);

  fclose(f);
}

void saveMeshDataMaterials(const char* fileName, const MeshData& m)
{
  FILE* f = fopen(fileName, "wb");

  if (!f) {
    printf("Error opening file '%s' for writing.\n", fileName);
    assert(false);
    exit(EXIT_FAILURE);
  }

  const uint64_t numMaterials  = m.materials.size();
  const uint64_t materialsSize = m.materials.size() * sizeof(Material);

  fwrite(&numMaterials, 1, sizeof(numMaterials), f);
  fwrite(&materialsSize, 1, sizeof(materialsSize), f);
  fwrite(m.materials.data(), sizeof(Material), numMaterials, f);

  saveStringList(f, m.textureFiles);

  fclose(f);
}

void saveBoundingBoxes(const char* fileName, const std::vector<BoundingBox>& boxes)
{
  FILE* f = fopen(fileName, "wb");

  if (!f) {
    printf("Error opening bounding boxes file '%s' for writing.\n", fileName);
    assert(false);
    exit(EXIT_FAILURE);
  }

  const uint32_t sz = (uint32_t)boxes.size();
  fwrite(&sz, 1, sizeof(sz), f);
  fwrite(boxes.data(), sz, sizeof(BoundingBox), f);

  fclose(f);
}

void loadBoundingBoxes(const char* fileName, std::vector<BoundingBox>& boxes)
{
  FILE* f = fopen(fileName, "rb");

  if (!f) {
    printf("Error opening bounding boxes file '%s'\n", fileName);
    assert(false);
    exit(EXIT_FAILURE);
  }

  uint32_t sz;
  fread(&sz, 1, sizeof(sz), f);

  // TODO: check file size, divide by bounding box size
  boxes.resize(sz);
  fread(boxes.data(), sz, sizeof(BoundingBox), f);

  fclose(f);
}

// combine a collection of meshes into a single MeshData container
MeshFileHeader mergeMeshData(MeshData& m, const std::vector<MeshData*> md)
{
  uint32_t numTotalVertices = 0;
  uint32_t numTotalIndices  = 0;

  if (!md.empty()) {
    m.streams = md[0]->streams;
  }

  const uint32_t vertexSize = m.streams.getVertexSize();

  uint32_t offset    = 0;
  uint32_t mtlOffset = 0;

  for (const MeshData* i : md) {
    LVK_ASSERT(m.streams == i->streams);
    mergeVectors(m.indexData, i->indexData);
    mergeVectors(m.vertexData, i->vertexData);
    mergeVectors(m.meshes, i->meshes);
    mergeVectors(m.boxes, i->boxes);

    for (size_t j = 0; j != i->meshes.size(); j++) {
      // m.vertexCount, m.lodCount and m.streamCount do not change
      // m.vertexOffset also does not change, because vertex offsets are local (i.e., baked into the indices)
      m.meshes[offset + j].indexOffset += numTotalIndices;
      m.meshes[offset + j].materialID += mtlOffset;
    }

    // shift individual indices
    for (size_t j = 0; j != i->indexData.size(); j++) {
      m.indexData[numTotalIndices + j] += numTotalVertices;
    }

    offset += (uint32_t)i->meshes.size();
    mtlOffset += (uint32_t)i->materials.size();

    numTotalIndices += (uint32_t)i->indexData.size();
    numTotalVertices += (uint32_t)i->vertexData.size() / vertexSize;
  }

  return MeshFileHeader{
    .magicValue     = 0x12345678,
    .meshCount      = (uint32_t)offset,
    .indexDataSize  = static_cast<uint32_t>(numTotalIndices * sizeof(uint32_t)),
    .vertexDataSize = static_cast<uint32_t>(m.vertexData.size()),
  };
}

void recalculateBoundingBoxes(MeshData& m)
{
  LVK_ASSERT(m.streams.attributes[0].format == lvk::VertexFormat::Float3);

  const uint32_t stride = m.streams.getVertexSize();

  m.boxes.clear();
  m.boxes.reserve(m.meshes.size());

  for (const Mesh& mesh : m.meshes) {
    const uint32_t numIndices = mesh.getLODIndicesCount(0);

    glm::vec3 vmin(std::numeric_limits<float>::max());
    glm::vec3 vmax(std::numeric_limits<float>::lowest());

    for (uint32_t i = 0; i != numIndices; i++) {
      const uint32_t vtxOffset = m.indexData[mesh.indexOffset + i] + mesh.vertexOffset;
      const float* vf          = (const float*)&m.vertexData[vtxOffset * stride];

      vmin = glm::min(vmin, vec3(vf[0], vf[1], vf[2]));
      vmax = glm::max(vmax, vec3(vf[0], vf[1], vf[2]));
    }

    m.boxes.emplace_back(vmin, vmax);
  }
}