// Include standard headers
#include <stdio.h>
#include <stdlib.h>

// Include GLEW
#include <GL/glew.h>

// Include GLFW
#include <GLFW/glfw3.h>

// Include shader
#include "shader.h"

GLFWwindow* window;

int main(void) {

	// Initialise GLFW
	if(!glfwInit()) {
		fprintf(stderr, "Failed to initialize GLFW\n");
		getchar();
		return -1;
	}

	glfwWindowHint(GLFW_SAMPLES, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // To make MacOS happy; should not be needed
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	// Open a window and create its OpenGL context
	window = glfwCreateWindow(1024, 768, "OpenGL Clock", NULL, NULL);
	if (window == NULL) {
		fprintf(stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.\n");
		getchar();
		glfwTerminate();
		return -1;
	}

	glfwMakeContextCurrent(window);

	// Initialize GLEW
	if (glewInit() != GLEW_OK) {
		fprintf(stderr, "Failed to initialize GLEW\n");
		getchar();
		glfwTerminate();
		return -1;
	}

	// Ensure we can capture the escape key being pressed below
	glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);

	// Dark grey background
	glClearColor(0.15f, 0.15f, 0.15f, 0.0f);

	GLuint VertexArrayID;
	glGenVertexArrays(1, &VertexArrayID);
	glBindVertexArray(VertexArrayID);

	// Create and compile our GLSL program from the shaders
	GLuint programID;
    if (LoadShaders(&programID,
                    "../shaders/SimpleVertexShader.vertexshader",
                    "../shaders/SimpleFragmentShader.fragmentshader")) {
        fprintf(stderr, "Could not load shaders.\n");
        return -1;
    }

	static const GLfloat g_vertex_buffer_data[] = { 
		-1.0f, -1.0f, 0.0f,
		 1.0f, -1.0f, 0.0f,
		 0.0f,  1.0f, 0.0f
	};

	GLuint vertexbuffer;
	glGenBuffers(1, &vertexbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);

	do {
		// Clear the screen. It's not mentioned before Tutorial 02,
        // but it can cause flickering, so it's there nonetheless.
		glClear(GL_COLOR_BUFFER_BIT);

		// Use our shader
		glUseProgram(programID);

		// 1rst attribute buffer : vertices
		glEnableVertexAttribArray(0);
		glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
		glVertexAttribPointer(
			0,                  // attribute 0. No particular reason for 0, but must match the layout in the shader.
			3,                  // size
			GL_FLOAT,           // type
			GL_FALSE,           // normalized?
			0,                  // stride
			NULL                // array buffer offset
		);

		// Draw the triangle !
		glDrawArrays(GL_TRIANGLES, 0, 3); // 3 indices starting at 0 -> 1 triangle

		glDisableVertexAttribArray(0);
		
		// Swap buffers
		glfwSwapBuffers(window);
		glfwPollEvents();

        // Check if the ESC key was pressed or the window was closed
	} while(glfwGetKey(window, GLFW_KEY_ESCAPE) != GLFW_PRESS &&
		   glfwWindowShouldClose(window) == 0);

	// Close OpenGL window and terminate GLFW
	glfwTerminate();

	return 0;
}