#include "opengl/handles/shader_program_handle.hpp"

#include <string_view>
// TODO remove
#include "opengl/error.hpp"
#include "util/logger.hpp"

namespace zgl
{

shader_program_handle::attribute_support_type shader_program_handle::check_attribute_support(
	const std::span<const shader_program_variable> attributes
) const {
	auto attribute_candidates = attribute_support_type{};

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

	auto curr_attribute_flag = attribute_support_type{ 1 };
	for (const auto& attribute : attributes) {
		const auto location = glGetAttribLocation(program_id, attribute.name);
		if (location == attribute.info.location)
		{
			attribute_candidates |= curr_attribute_flag;
		}
		curr_attribute_flag <<= 1;
	}

	auto supported_attributes = attribute_support_type{};

	GLint count;
	glGetProgramiv(program_id, GL_ACTIVE_ATTRIBUTES, &count);
	if (check_error()) ztu::logger::error("GL_err: %", error.message());

	for (GLint i{}; i != count and attribute_candidates; ++i)
	{
		GLenum type;
		GLint size;
		GLsizei name_length;
		auto name = std::array<char, 256>{};
		glGetActiveAttrib(
			program_id, i,
			name.size(),
			&name_length,
			&size, &type,
			name.data()
		);
		if (check_error()) ztu::logger::error("GL_err: %", error.message());

		const auto name_view = std::string_view(name.data(), name_length);

		auto attribute_index = attribute_support_type{};
		for (auto candidates = attribute_candidates; candidates; candidates >>= 1) {
			if (candidates & 1)
			{
				const auto& attribute = attributes[attribute_index];
				if (type == attribute.info.type and name_view == attribute.name)
				{
					const auto new_uniform_flag = attribute_support_type{ 1 } << attribute_index;
					supported_attributes |= new_uniform_flag;
					attribute_candidates ^= new_uniform_flag;
				}
			}
			++attribute_index;
		}
	}

	return supported_attributes;
}

shader_program_handle::uniform_support_type shader_program_handle::check_uniform_support(
	const std::span<const shader_program_variable> uniforms
) const {
	auto uniform_candidates = uniform_support_type{};

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

	auto curr_uniform_flag = uniform_support_type{ 1 };
	for (const auto& uniform : uniforms)
	{
		const auto location = glGetUniformLocation(program_id, uniform.name);

		if (location == uniform.info.location)
		{
			uniform_candidates |= curr_uniform_flag;
			ztu::logger::debug("[%] '%': %.", program_id, uniform.name, location);
		}
		else
		{
			ztu::logger::debug("Expected '%' at % but was %.", uniform.name, uniform.info.location, location);
		}
		curr_uniform_flag <<= 1;
	}

	auto supported_uniforms = uniform_support_type{};

	GLint count;
	glGetProgramiv(program_id, GL_ACTIVE_UNIFORMS, &count);
	if (check_error()) ztu::logger::error("GL_err: %", error.message());

	for (GLint i{}; i != count and uniform_candidates; ++i)
	{
		GLenum type;
		GLint size;
		GLsizei name_length;
		auto name = std::array<char, 256>{};
		glGetActiveUniform(
			program_id, i,
			name.size(),
			&name_length,
			&size, &type,
			name.data()
		);
		if (check_error()) ztu::logger::error("GL_err: %", error.message());

		const auto name_view = std::string_view(name.data(), name_length);

		auto uniform_index = uniform_support_type{};
		for (auto candidates = uniform_candidates; candidates; candidates >>= 1)
		{
			if (candidates & 1)
			{
				const auto& uniform = uniforms[uniform_index];
				if (type == uniform.info.type and name_view == uniform.name)
				{
					const auto new_uniform_flag = uniform_support_type{ 1 } << uniform_index;
					supported_uniforms |= new_uniform_flag;
					uniform_candidates ^= new_uniform_flag;
				}
			}
			++uniform_index;
		}
	}

	return supported_uniforms;
}
}