#pragma once

#include <array>
#include <glad/gl.h>
#include <glm/common.hpp>
#include <glm/fwd.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <span>

template<typename T> struct gl_traits;

struct gl_traits_base {
	static constexpr GLint size {1};
};

struct gl_traits_float : public gl_traits_base {
	template<GLenum type, GLint size>
	static GLuint
	vertexAttribFormatFunc(GLuint vao, GLuint index, GLuint offset)
	{
		glVertexArrayAttribFormat(vao, index, size, type, GL_FALSE, offset);
		return 1;
	}
};

struct gl_traits_longfloat : public gl_traits_base {
	template<GLenum type, GLint size>
	static GLuint
	vertexAttribFormatFunc(GLuint vao, GLuint index, GLuint offset)
	{
		glVertexArrayAttribLFormat(vao, index, size, type, offset);
		return 1;
	}
};

struct gl_traits_integer : public gl_traits_base {
	template<GLenum type, GLint size>
	static GLuint
	vertexAttribFormatFunc(GLuint vao, GLuint index, GLuint offset)
	{
		glVertexArrayAttribIFormat(vao, index, size, type, offset);
		return 1;
	}
};

template<> struct gl_traits<glm::f32> : public gl_traits_float {
	static constexpr GLenum type {GL_FLOAT};
	static constexpr auto glUniformFunc {&glUniform1f};
	static constexpr std::array glUniformvFunc {&glUniform1fv, &glUniform2fv, &glUniform3fv, &glUniform4fv};
	static constexpr std::array glUniformmFunc {&glUniformMatrix2fv, &glUniformMatrix3fv, &glUniformMatrix4fv};
	static constexpr auto glTextureParameterFunc {&glTextureParameterf};
	static constexpr auto glTextureParametervFunc {&glTextureParameterfv};
	static constexpr auto vertexArrayAttribFormat {&vertexAttribFormatFunc<type, 1>};
};

template<> struct gl_traits<glm::f64> : public gl_traits_longfloat {
	static constexpr GLenum type {GL_DOUBLE};
	static constexpr auto vertexArrayAttribFormat {&vertexAttribFormatFunc<type, 1>};
};

template<> struct gl_traits<glm::int8> : public gl_traits_integer {
	static constexpr GLenum type {GL_BYTE};
	static constexpr auto vertexArrayAttribFormat {&vertexAttribFormatFunc<type, 1>};
};

template<> struct gl_traits<glm::int16> : public gl_traits_integer {
	static constexpr GLenum type {GL_SHORT};
	static constexpr auto vertexArrayAttribFormat {&vertexAttribFormatFunc<type, 1>};
};

template<> struct gl_traits<glm::int32> : public gl_traits_integer {
	static constexpr GLenum type {GL_INT};
	static constexpr auto glUniformFunc {&glUniform1i};
	static constexpr std::array glUniformvFunc {&glUniform1iv, &glUniform2iv, &glUniform3iv, &glUniform4iv};
	static constexpr auto glTextureParameterFunc {&glTextureParameteri};
	static constexpr auto glTextureParametervFunc {&glTextureParameteriv};
	static constexpr auto vertexArrayAttribFormat {&vertexAttribFormatFunc<type, 1>};
};

template<> struct gl_traits<glm::uint8> : public gl_traits_integer {
	static constexpr GLenum type {GL_UNSIGNED_BYTE};
	static constexpr auto vertexArrayAttribFormat {&vertexAttribFormatFunc<type, 1>};
};

template<> struct gl_traits<glm::uint16> : public gl_traits_integer {
	static constexpr GLenum type {GL_UNSIGNED_SHORT};
	static constexpr auto vertexArrayAttribFormat {&vertexAttribFormatFunc<type, 1>};
};

template<> struct gl_traits<glm::uint32> : public gl_traits_integer {
	static constexpr GLenum type {GL_UNSIGNED_INT};
	static constexpr auto glUniformFunc {&glUniform1ui};
	static constexpr std::array<decltype(&glUniform1uiv), 5> glUniformvFunc {
			&glUniform1uiv, &glUniform2uiv, &glUniform3uiv, &glUniform4uiv};
	static constexpr auto vertexArrayAttribFormat {&vertexAttribFormatFunc<type, 1>};
};

template<typename T, std::size_t S> struct gl_traits<std::array<T, S>> : public gl_traits<T> {
	static constexpr GLint size {S * gl_traits<T>::size};
	static constexpr auto vertexArrayAttribFormat {[](GLuint vao, GLuint index, GLuint offset) {
		if constexpr (std::is_pod_v<T>) {
			return gl_traits<T>::template vertexAttribFormatFunc<gl_traits<T>::type, S>(vao, index, offset);
		}
		else {
			GLuint used = 0;
			for (GLuint e = 0; e < S; e++) {
				used += gl_traits<T>::template vertexAttribFormatFunc<gl_traits<T>::type, 1>(
						vao, index + e, offset + (e * sizeof(T)));
			}
			return used;
		}
	}};
};

template<glm::length_t L, typename T, glm::qualifier Q> struct gl_traits<glm::vec<L, T, Q>> : public gl_traits<T> {
	static constexpr GLint size {L};
	static constexpr auto vertexArrayAttribFormat {[](GLuint vao, GLuint index, GLuint offset) {
		return gl_traits<T>::template vertexAttribFormatFunc<gl_traits<T>::type, L>(vao, index, offset);
	}};
};

template<glm::length_t C, glm::length_t R, typename T, glm::qualifier Q>
struct gl_traits<glm::mat<C, R, T, Q>> : public gl_traits<T> {
	static constexpr GLint size {C * R};
	static constexpr auto vertexArrayAttribFormat {[](GLuint vao, GLuint index, GLuint offset) {
		GLuint used = 0;
		for (GLuint row = 0; row < R; row++) {
			used += gl_traits<T>::template vertexAttribFormatFunc<gl_traits<T>::type, C>(
					vao, index + row, offset + (C * row * static_cast<GLuint>(sizeof(T))));
		}
		return used;
	}};
};

template<typename T>
concept has_glUniform1 = requires { gl_traits<T>::glUniformFunc; };
template<typename T>
concept has_glUniformNv = requires { gl_traits<T>::glUniformvFunc; };
template<typename T>
concept has_glUniformMatrixNv = requires { gl_traits<T>::glUniformmFunc; };
template<typename T>
concept has_glTextureParameter = requires { gl_traits<T>::glTextureParameterFunc; };
template<typename T>
concept has_glTextureParameterv = requires { gl_traits<T>::glTextureParametervFunc; };

template<has_glUniform1 T>
void
glUniform(GLint location, T v)
{
	(*gl_traits<T>::glUniformFunc)(location, v);
}

template<glm::length_t L, has_glUniformNv T, glm::qualifier Q>
void
glUniform(GLint location, const glm::vec<L, T, Q> & v)
{
	(*gl_traits<T>::glUniformvFunc[L - 1])(location, 1, glm::value_ptr(v));
}

template<glm::length_t L, has_glUniformNv T, glm::qualifier Q>
void
glUniform(GLint location, std::span<const glm::vec<L, T, Q>> v)
{
	(*gl_traits<T>::glUniformvFunc[L - 1])(location, static_cast<GLsizei>(v.size()), glm::value_ptr(v.front()));
}

template<has_glUniformNv T>
void
glUniform(GLint location, std::span<const T> v)
{
	(*gl_traits<T>::glUniformvFunc.front())(location, static_cast<GLsizei>(v.size()), v.data());
}

template<glm::length_t L, has_glUniformMatrixNv T, glm::qualifier Q>
void
glUniform(GLint location, const glm::mat<L, L, T, Q> & v)
{
	(*gl_traits<T>::glUniformmFunc[L - 2])(location, 1, GL_FALSE, glm::value_ptr(v));
}

template<glm::length_t L, has_glUniformMatrixNv T, glm::qualifier Q>
void
glUniform(GLint location, std::span<const glm::mat<L, L, T, Q>> v)
{
	(*gl_traits<T>::glUniformmFunc[L - 2])(
			location, static_cast<GLsizei>(v.size()), GL_FALSE, glm::value_ptr(v.front()));
}