#include "xe_model.hpp"
#include "xe_utils.hpp"

#define TINYOBJLOADER_IMPLEMENTATION
#include "xe_obj_loader.hpp"

#define GLM_ENABLE_EXPERIMENTAL
#include <glm/gtx/hash.hpp>

#include <cassert>
#include <cstring>
#include <unordered_map>

namespace std {
template<>
struct hash<xe::Model::Vertex> {
  size_t operator()(xe::Model::Vertex const &vertex) const {
    size_t seed = 0;
    xe::hashCombine(seed, vertex.position, vertex.normal, vertex.uv);
    return seed;
  }
};
}

namespace xe {

Model::Model(Device &device, const Model::Builder &builder) : xeDevice{device} {
  createVertexBuffers(builder.vertices);
  createIndexBuffers(builder.indices);
}

Model::~Model() {}

std::unique_ptr<Model> Model::createModelFromFile(Device &device, const std::string &filepath) {
  Builder builder{};
  builder.loadModel(filepath);
  return std::make_unique<Model>(device, builder);
}

void Model::createVertexBuffers(const std::vector<Vertex> &vertices) {
  vertexCount = static_cast<uint32_t>(vertices.size());
  assert(vertexCount >= 3 && "Vertex count must be atleast 3");
  VkDeviceSize bufferSize = sizeof(vertices[0]) * vertexCount;
  uint32_t vertexSize = sizeof(vertices[0]);
 
  Buffer stagingBuffer {
    xeDevice,
    vertexSize,
    vertexCount,
    VK_BUFFER_USAGE_TRANSFER_SRC_BIT,
    VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT | VK_MEMORY_PROPERTY_HOST_COHERENT_BIT
  };

  stagingBuffer.map();
  stagingBuffer.writeToBuffer((void *)vertices.data());

  vertexBuffer = std::make_unique<Buffer>(
    xeDevice,
    vertexSize,
    vertexCount,
    VK_BUFFER_USAGE_VERTEX_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT,
    VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT
  );

  xeDevice.copyBuffer(stagingBuffer.getBuffer(), vertexBuffer->getBuffer(), bufferSize);
}

void Model::createIndexBuffers(const std::vector<uint32_t> &indices) {
  indexCount = static_cast<uint32_t>(indices.size());
  hasIndexBuffer = indexCount > 0;

  if (!hasIndexBuffer) {
    return;
  }

  VkDeviceSize bufferSize = sizeof(indices[0]) * indexCount;
  uint32_t indexSize = sizeof(indices[0]);

  Buffer stagingBuffer {
    xeDevice,
    indexSize,
    indexCount,
    VK_BUFFER_USAGE_TRANSFER_SRC_BIT,
    VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT | VK_MEMORY_PROPERTY_HOST_COHERENT_BIT
  };

  stagingBuffer.map();
  stagingBuffer.writeToBuffer((void *)indices.data());

  indexBuffer = std::make_unique<Buffer>(
    xeDevice,
    indexSize,
    indexCount,
    VK_BUFFER_USAGE_INDEX_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT,
    VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT
  );

  xeDevice.copyBuffer(stagingBuffer.getBuffer(), indexBuffer->getBuffer(), bufferSize);
}

void Model::bind(VkCommandBuffer commandBuffer) {
  VkBuffer buffers[] = {vertexBuffer->getBuffer()};
  VkDeviceSize offsets[] = {0};
  vkCmdBindVertexBuffers(commandBuffer, 0, 1, buffers, offsets);

  if (hasIndexBuffer) {
    vkCmdBindIndexBuffer(commandBuffer, indexBuffer->getBuffer(), 0, VK_INDEX_TYPE_UINT32);
  }
}

void Model::draw(VkCommandBuffer commandBuffer) {
  if (hasIndexBuffer) {
    vkCmdDrawIndexed(commandBuffer, indexCount, 1, 0, 0, 0);
  } else {
    vkCmdDraw(commandBuffer, vertexCount, 1, 0, 0);
  }
}

std::vector<VkVertexInputBindingDescription> Model::Vertex::getBindingDescriptions() {
  std::vector<VkVertexInputBindingDescription> bindingDescriptions(1);
  bindingDescriptions[0].binding = 0;
  bindingDescriptions[0].stride = sizeof(Vertex);
  bindingDescriptions[0].inputRate = VK_VERTEX_INPUT_RATE_VERTEX;
  return bindingDescriptions;
}

std::vector<VkVertexInputAttributeDescription> Model::Vertex::getAttributeDescriptions() {
  std::vector<VkVertexInputAttributeDescription> attributeDescptions{};

  attributeDescptions.push_back({0, 0, VK_FORMAT_R32G32B32_SFLOAT, offsetof(Vertex, position)});
  attributeDescptions.push_back({1, 0, VK_FORMAT_R32G32B32_SFLOAT, offsetof(Vertex, color)});
  attributeDescptions.push_back({2, 0, VK_FORMAT_R32G32B32_SFLOAT, offsetof(Vertex, normal)});
  attributeDescptions.push_back({3, 0, VK_FORMAT_R32G32_SFLOAT, offsetof(Vertex, uv)});

  return attributeDescptions;
}

void Model::Builder::loadModel(const std::string &filepath) {
  tinyobj::attrib_t attrib;
  std::vector<tinyobj::shape_t> shapes;
  std::vector<tinyobj::material_t> materials;
  std::string warn, err;
  if (!tinyobj::LoadObj(&attrib, &shapes, &materials, &warn, &err, filepath.c_str())) {
    throw std::runtime_error(warn + err);
  }

  vertices.clear();
  indices.clear();

  std::unordered_map<Vertex, uint32_t> uniqueVertices{};
  for (const auto &shape : shapes) {
    for (const auto &index : shape.mesh.indices) {
      Vertex vertex{};

      if(index.vertex_index >= 0) {
        vertex.position = {
          attrib.vertices[3 * index.vertex_index + 0],
          attrib.vertices[3 * index.vertex_index + 1],
          attrib.vertices[3 * index.vertex_index + 2]
        };

        vertex.color = {
          attrib.colors[3 * index.vertex_index + 0],
          attrib.colors[3 * index.vertex_index + 1],
          attrib.colors[3 * index.vertex_index + 2]
        };
      }

      if(index.normal_index >= 0) {
        vertex.normal = {
          attrib.normals[3 * index.normal_index + 0],
          attrib.normals[3 * index.normal_index + 1],
          attrib.normals[3 * index.normal_index + 2]
        };
      }

      if(index.texcoord_index >= 0) {
        vertex.uv = {
          attrib.texcoords[2 * index.texcoord_index + 0],
          attrib.texcoords[2 * index.texcoord_index + 1],
        };
      }

      if (uniqueVertices.count(vertex) == 0) {
        uniqueVertices[vertex] = static_cast<uint32_t>(vertices.size());
        vertices.push_back(vertex);
      }
      indices.push_back(uniqueVertices[vertex]);
    }
  }
}

}