#pragma once

#include <GL/gl3w.h>

#include "entity.h"
#include "util.h"


struct Entity;

// TODO: can these structs be used as opaque pointers?
struct gl_buffer
{
	GLuint buffer_id = 0;
	size_t buffer_len = 0; // NOTE: number of elements in buffer
	GLfloat* buffer = nullptr;
};

struct gl_index_buffer
{
	GLuint buffer_id = 0;
	size_t buffer_len = 0;
	uint* buffer = nullptr;
};

struct render_object
{
	gl_buffer vertex_buffer;
	gl_buffer normal_buffer;
	gl_buffer color_buffer;
	gl_index_buffer index_buffer;
};

struct rg_shader_program
{
	GLuint program_id = 0;
	GLuint model_matrix_id = 0;
	GLuint view_matrix_id = 0;
	GLuint projection_matrix_id = 0;
	GLuint normal_matrix_id = 0;
	GLuint vertex_array_id = 0;
	GLuint num_lights_id = 0;
};

struct render_group
{
	uint num_objects = 0;
	render_object** render_objects = nullptr;
	rg_shader_program shader;
	bool use_normals = false;
	bool draw_indexed = false;
	GLenum draw_mode = GL_TRIANGLES;
};

// TODO: maybe pull out to seperate header
struct rg_point_light
{
	uint light_ID;
	glm::vec3 position;
	glm::vec3 color;
	float intensity;
};

// NOTE: initializes a render_group with 1 render_object allocated
render_group* rgInitSingle(rg_shader_program& sp, uint vertex_buffer_len,
						bool use_normals = false, uint index_buffer_len = 0,
						GLenum draw_mode = GL_TRIANGLES);

bool rgInitShaderProgram(rg_shader_program& sp, const char * vertex_code, const char * frag_code);

bool rgInitEntity(Entity* e);

void rgBufferData(gl_buffer* buffer, GLenum usage, GLenum target);

void rgDraw(render_group* rg, glm::mat4 model_matrix,
		glm::mat4 view_matrix, glm::mat4 projection_matrix,
		rg_point_light* lights, uint num_lights,
		bool update_vertex_data = false, bool update_color_data = false);

void rgFree(render_group* rg);