#include "opengl/data/mesh_data.hpp"

#include "opengl/type_utils.hpp"
#include "opengl/error.hpp"

#include "GL/glew.h"
#include <algorithm>
#include "util/logger.hpp" // TODO remove


std::error_code zgl::mesh_data::build_from(
	const std::span<const ztu::u8> vertex_buffer,
	const std::span<const GLenum> component_types,
	const std::span<const GLint> component_lengths,
	const GLsizei stride,
	const std::span<const ztu::u32> index_buffer,
	const ztu::u32 material_id,
	const components::mesh_vertex::flags components,
	mesh_data& data
) {
	if (not std::ranges::all_of(component_types, type_utils::is_valid_type))
	{
		ztu::logger::debug("not all types valid.");
		return std::make_error_code(std::errc::invalid_argument);
	}

	const auto vertices_byte_count = vertex_buffer.size() * sizeof(std::uint8_t);
	if (vertices_byte_count > std::numeric_limits<GLsizeiptr>::max())
	{
		return std::make_error_code(std::errc::value_too_large);
	}

	const auto indices_byte_count = index_buffer.size() * sizeof(ztu::u32);
	if (indices_byte_count > std::numeric_limits<GLsizeiptr>::max())
	{
		return std::make_error_code(std::errc::value_too_large);
	}

	auto error = std::error_code{};

	auto check_error = [&error, ec = static_cast<GLenum>(GL_NO_ERROR)]() mutable -> const std::error_code&
	{
		ec = glGetError();
		if (ec != GL_NO_ERROR)
		{
			error = make_error_code(ec);
		}
		return error;
	};

	GLuint vao_id;
	glGenVertexArrays(1, &vao_id);
	glBindVertexArray(vao_id);
	if (check_error()) return error;

	ztu::logger::debug("Created mesh vao: % valid: %", vao_id, (bool)glIsVertexArray(vao_id));

	GLuint vertex_buffer_id;
	glGenBuffers(1, &vertex_buffer_id);
	glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer_id);
	glBufferData(
		GL_ARRAY_BUFFER,
		static_cast<GLsizeiptr>(vertices_byte_count),
		vertex_buffer.data(),
		GL_STATIC_DRAW
	);
	if (check_error()) return error;

	GLuint index_buffer_id;
	glGenBuffers(1, &index_buffer_id);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, index_buffer_id);
	glBufferData(
		GL_ELEMENT_ARRAY_BUFFER,
		static_cast<GLsizeiptr>(indices_byte_count),
		index_buffer.data(),
		GL_STATIC_DRAW
	);
	if (check_error()) return error;

	glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer_id);
	if (check_error()) return error;

	auto offset = GLsizei{ 0 };

	for (std::size_t i{}; i != component_types.size(); ++i)
	{
		const auto type = component_types[i];
		const auto length = component_lengths[i];
		const auto byte_count = type_utils::size_of(type);

		glVertexAttribPointer(
			i,
			length,
			type,
			GL_FALSE,
			stride,
			reinterpret_cast<GLvoid*>(offset)
		);

		glEnableVertexAttribArray(i);
		if (check_error()) return error;

		offset += length * byte_count;
	}

	glBindBuffer(GL_ARRAY_BUFFER, 0);
	glBindVertexArray(0);

	data = mesh_data(
		vertex_buffer_id,
		index_buffer_id,
		vao_id,
		material_id,
		components,
		index_buffer.size()
	);

	return {};
}