#include <stdlib.h>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <sys/time.h>
#include <time.h>

#include "shader.h"
#include "die.h"
#include "config.h"

#include "fill_vert.h"
#include "visuals_frag.h"

void prepare_tri() {
	const float vertices[] = {
		0, 1, 0,
		1, -1, 0,
		-1, -1, 0,
	};

	// initialize vertex {buffer,attribute} object buffers
	GLuint VBO, VAO;
	glGenBuffers(1, &VBO);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	glGenVertexArrays(1, &VAO);
	glBindVertexArray(VAO);

	// copy vertex data into VBO
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

	// set VAO pointers
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(0);

	// draw (only) this triangle
	glBindBuffer(GL_ARRAY_BUFFER, 0);
	glBindVertexArray(VAO);
}

int main(int argc, char** argv) {
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	// force floating window w/ i3
	glfwWindowHint(GLFW_FLOATING, GL_TRUE);
	glfwWindowHint(GLFW_RESIZABLE, GLFW_FALSE);

	// initialize window
	GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "vis", NULL, NULL);
	if (window == NULL)
		die("error: could not create window\n");
	glfwMakeContextCurrent(window);

	// initialize GLEW
	glewInit();

	// create single triangle
	prepare_tri();

	// prepare shaders
	GLuint shader = link_shaders(
		vert_shader(fill_vert, fill_vert_size),
		frag_shader(visuals_frag, visuals_frag_size)
	);

	// prepare uniform variables
	GLint u_time = glGetUniformLocation(shader, "time");
	int time_start = time(NULL);

	// main draw loop
	while (!glfwWindowShouldClose(window)) {
		glfwPollEvents();

		// set `time` uniform
		struct timeval t;
		gettimeofday(&t, NULL);
		t.tv_sec -= time_start;
		float time = t.tv_sec + (t.tv_usec / 1e6);
		glUniform1f(u_time, time);

		glUseProgram(shader);
		glDrawArrays(GL_TRIANGLES, 0, 3);

		glfwSwapBuffers(window);
	}

	return EXIT_SUCCESS;
}