#include <glad/glad.h>
#include <iostream>
#include <GLFW/glfw3.h>
#include <cmath>
#include "shader.h"

const char *vertexShaderSource = "#version 330 core\n"
    "layout (location = 0) in vec3 aPos;\n"
    "layout (location = 1) in vec3 aColor;\n"
    "\n"
    "out vec3 ourColor;\n"
    "\n"
    "void main()\n"
    "{\n"
    "   gl_Position = vec4(aPos, 1.0);\n"
    "   ourColor = aColor;"
    "}\0";

const char *fragmentShaderSource = "#version 330 core\n"
    "out vec4 FragColor;\n"
    "in vec3 ourColor;\n"
    "\n"
    "void main()\n"
    "{\n"
    "    FragColor = vec4(ourColor, 1.0);\n"
    "}\0";

void framebuffer_size_callback(GLFWwindow* window, int width, int height);

void processInput(GLFWwindow *window);

int main()
{
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
	
	GLFWwindow* window = glfwCreateWindow(
						800, 
						600, 
						"My OpenGL project", 
						NULL, 
						NULL
					     );
	if (window == NULL) {
		std::cout << "Failed to create GLFW window" << std::endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);

	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
		std::cout << "Failed to initialize GLAD" << std::endl;
		return -1;
	}    

	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
	
	// вершины фигуры
	float vertices[] = {
		// координаты 	      // цвета
    		-0.5f, -0.5f, 0.0f,   1.0f, 0.0f, 0.0f,
    		 0.5f, -0.5f, 0.0f,   0.0f, 1.0f, 0.0f,
    		 0.0f,  0.5f, 0.0f,   0.0f, 0.0f, 1.0f,
	};  
	unsigned int indices[] = {
		0, 1, 2, // первый треугольник
	};


	// ШЕЙДЕРЫ
	Shader ourShader("./shader.vs", "./shader.fs");
	
	// ИНИЦИАЛИЗАЦИЯ VAO
	unsigned int VBO, VAO, EBO;
	glGenVertexArrays(1, &VAO);
	glGenBuffers(1, &VBO);
	glGenBuffers(1, &EBO);
	glBindVertexArray(VAO);

	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	glBufferData(
			GL_ARRAY_BUFFER, 
			sizeof(vertices), 
			vertices, 
			GL_STATIC_DRAW
		    );

	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
	glBufferData(
			GL_ELEMENT_ARRAY_BUFFER, 
			sizeof(indices), 
			indices,
			GL_STATIC_DRAW
		    );

	glVertexAttribPointer(
				0, 
				3, 
				GL_FLOAT, 
				GL_FALSE, 
				6 * sizeof(float), 
				(void*)0
			     );
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(
				1, 
				3, 
				GL_FLOAT, 
				GL_FALSE, 
				6 * sizeof(float), 
				(void*)(3* sizeof(float))
			     );
	glEnableVertexAttribArray(1);

	#if WIREFRAME == 1
	glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
	#endif
	
	while (!glfwWindowShouldClose(window)) {
		processInput(window);

		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);
		
		ourShader.use();

		glBindVertexArray(VAO);
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

		glfwSwapBuffers(window);
		glfwPollEvents();
	}

	glfwTerminate();

	return 0;
}

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    glViewport(0, 0, width, height);
}

void processInput(GLFWwindow *window)
{
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
		glfwSetWindowShouldClose(window, true);
}