#include <stdlib.h>
#include <stdbool.h>
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <lua.h>
#include <lauxlib.h>
#include "util/util.h"
#include "gl.h"

int gl_create_buffer(lua_State *L);
int gl_bind_buffer(lua_State *L);
int gl_buffer_data(lua_State *L);

int gl_vertex_array_create(lua_State *L);
int gl_vertex_array_bind(lua_State *L);
int gl_vertex_attrib_pointer(lua_State *L);
int gl_vertex_array_enable_attrib(lua_State *L);


void setup_data(lua_State *L, int gl_index)
{
	struct honey_tbl_t tbl[] = {
		/* functions */
		H_FUNC("GenBuffers", gl_create_buffer),
		H_FUNC("BindBuffer", gl_bind_buffer),
		H_FUNC("BufferData", gl_buffer_data),

		H_FUNC("GenVertexArrays", gl_vertex_array_create),
		H_FUNC("BindVertexArray", gl_vertex_array_bind),
		H_FUNC("VertexAttribPointer", gl_vertex_attrib_pointer),
		H_FUNC("EnableVertexAttribArray", gl_vertex_array_enable_attrib),

		/******** enums ********/
		/* buffer bind targets */
		H_INT("ARRAY_BUFFER", GL_ARRAY_BUFFER),
		H_INT("ELEMENT_ARRAY_BUFFER", GL_ELEMENT_ARRAY_BUFFER),

		/* buffer usage patters */
		H_INT("STREAM_DRAW", GL_STREAM_DRAW),
		H_INT("STATIC_DRAW", GL_STATIC_DRAW),
		H_INT("DYNAMIC_DRAW", GL_DYNAMIC_DRAW),

		H_END
	};	
	create_table(L, tbl);
	append_table(L, gl_index, lua_gettop(L));
	lua_pop(L, 1);
}


int gl_create_buffer(lua_State *L)
{
	int buf;
	glGenBuffers(1, &buf);
	lua_pushinteger(L, buf);
	return 1;
}


int gl_bind_buffer(lua_State *L)
{
	int target = luaL_checkinteger(L, 1);
	int buf = luaL_checkinteger(L, 2);
	glBindBuffer(target, buf);
	return 0;
}


#define GET_BUFFER_TYPE(type, name, conversion) \
	void * get_buffer_ ## name (lua_State *L, size_t *sz, int tbl) { \
		size_t len = lua_objlen(L, tbl); \
		*sz = len * sizeof(type); \
		type *buf = malloc(*sz); \
		if (buf == NULL) \
			luaL_error(L, "failed to allocate intermediary buffer"); \
		for (int i=0; i<len; i++) { \
			lua_rawgeti(L, tbl, i+1); \
			if (!lua_isnumber(L, -1)) \
				luaL_error(L, "all elements must be numbers (failed at index %d)", i); \
			buf[i] = conversion(L, -1); \
			lua_pop(L, 1); \
		} \
		return buf; \
	}

GET_BUFFER_TYPE(unsigned int, uint, lua_tointeger)
GET_BUFFER_TYPE(int, int, lua_tointeger)
GET_BUFFER_TYPE(float, float, lua_tonumber)

int gl_buffer_data(lua_State *L)
{
	lua_Integer target, type, usage;
	target = luaL_checkinteger(L, 1);
	type = luaL_checkinteger(L, 2);
	luaL_checktype(L, 3, LUA_TTABLE);
	int table = 3;
	usage = luaL_checkinteger(L, 4);

	/* build raw buffer */
	void *buf; size_t len;
	switch(type) {
	case GL_UNSIGNED_INT:
		buf = get_buffer_uint(L, &len, table);
		break;

	case GL_INT:
		buf = get_buffer_int(L, &len, table);
		break;

	case GL_FLOAT:
		buf = get_buffer_float(L, &len, table);
		break;

	default:
		luaL_error(L, "invalid type");
	}

	/* call */
	glBufferData(target, len, buf, usage);
	free(buf);
	return 0;
}


int gl_vertex_array_create(lua_State *L)
{
	int array;
	glGenVertexArrays(1, &array);
	lua_pushinteger(L, array);
	return 1;
}


int gl_vertex_array_bind(lua_State *L)
{
	lua_Integer array = luaL_checkinteger(L, 1);
	glBindVertexArray(array);
	return 0;
}


int gl_vertex_attrib_pointer(lua_State *L)
{
	lua_Integer index, size, stride, offset;
	bool normalized;
	index = luaL_checkinteger(L, 1);
	size = luaL_checkinteger(L, 2);
	normalized = lua_toboolean(L, 3);
	stride = luaL_checkinteger(L, 4);
	offset = luaL_checkinteger(L, 5);

	glVertexAttribPointer(index, size, GL_FLOAT, 
	                      normalized, stride*sizeof(float), 
	                      (void*) (offset*sizeof(float)));
	return 0;
}


int gl_vertex_array_enable_attrib(lua_State *L)
{
	lua_Integer index = luaL_checkinteger(L, 1);
	glEnableVertexAttribArray(index);
	return 0;
}