#include "mesh.h"
#include "obj_loader.h"
#include "vertex.hpp"
#include <memory>
#include <vector>

Mesh::Mesh(const std::string & fileName) : Mesh(OBJModel(fileName).ToIndexedModel()) { }

Mesh::Mesh(const IndexedModel & model) :
	m_vertexArrayObject {}, m_vertexArrayBuffers {}, m_numIndices {model.indices.size()}
{
	glGenVertexArrays(1, &m_vertexArrayObject);
	glBindVertexArray(m_vertexArrayObject);

	glGenBuffers(NUM_BUFFERS, m_vertexArrayBuffers.data());

	glBindBuffer(GL_ARRAY_BUFFER, m_vertexArrayBuffers[POSITION_VB]);
	glBufferData(
			GL_ARRAY_BUFFER, sizeof(model.positions[0]) * model.positions.size(), &model.positions[0], GL_STATIC_DRAW);
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, nullptr);

	glBindBuffer(GL_ARRAY_BUFFER, m_vertexArrayBuffers[TEXCOORD_VB]);
	glBufferData(
			GL_ARRAY_BUFFER, sizeof(model.texCoords[0]) * model.texCoords.size(), &model.texCoords[0], GL_STATIC_DRAW);
	glEnableVertexAttribArray(1);
	glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, nullptr);

	glBindBuffer(GL_ARRAY_BUFFER, m_vertexArrayBuffers[NORMAL_VB]);
	glBufferData(GL_ARRAY_BUFFER, sizeof(model.normals[0]) * model.normals.size(), &model.normals[0], GL_STATIC_DRAW);
	glEnableVertexAttribArray(2);
	glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, 0, nullptr);

	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_vertexArrayBuffers[INDEX_VB]);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(model.indices[0]) * model.indices.size(), &model.indices[0],
			GL_STATIC_DRAW);

	glBindVertexArray(0);
}

Mesh::Mesh(std::span<Vertex> vertices, std::span<unsigned int> indices) :
	m_vertexArrayObject {}, m_vertexArrayBuffers {}, m_numIndices {indices.size()}
{
	glGenVertexArrays(1, &m_vertexArrayObject);
	glBindVertexArray(m_vertexArrayObject);

	glGenBuffers(2, m_vertexArrayBuffers.data());

	glBindBuffer(GL_ARRAY_BUFFER, m_vertexArrayBuffers[0]);
	glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex) * vertices.size(), vertices.data(), GL_STATIC_DRAW);

	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void *)offsetof(Vertex, pos));

	glEnableVertexAttribArray(1);
	glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void *)offsetof(Vertex, texCoord));

	glEnableVertexAttribArray(2);
	glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void *)offsetof(Vertex, normal));

	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_vertexArrayBuffers[1]);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices[0]) * indices.size(), indices.data(), GL_STATIC_DRAW);

	glBindVertexArray(0);
}

Mesh::~Mesh()
{
	glDeleteBuffers(NUM_BUFFERS, m_vertexArrayBuffers.data());
	glDeleteVertexArrays(1, &m_vertexArrayObject);
}

void
Mesh::Draw() const
{
	glBindVertexArray(m_vertexArrayObject);

	glDrawElementsBaseVertex(GL_TRIANGLES, m_numIndices, GL_UNSIGNED_INT, nullptr, 0);

	glBindVertexArray(0);
}