#include <GL/glu.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <vector>

struct Point {
	int x, y;
};

int WIDTH = 640, HEIGHT = 480;
std::vector<Point> polygon;

void error_callback(int error, const char* description) {
	fputs(description, stderr);
}

void put_angles(GLFWwindow* window, int button, int action, int mods){
	if (button == GLFW_MOUSE_BUTTON_LEFT && action == GLFW_PRESS) {
		double x, y;
		glfwGetCursorPos(window, &x, &y);
		y = HEIGHT - (int)y;
		polygon.push_back({ (int)x, (int)y });
	}
}

void project(double width, double height) {
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(0, width, 0, height);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}

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

void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods) {
	if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS) {
		glfwSetWindowShouldClose(window, GL_TRUE);
	} else if (key == GLFW_KEY_SPACE && action == GLFW_PRESS) {
		polygon.push_back(polygon[0]);
	}
}

void init(GLFWwindow* window, int width, int height) {
	glfwMakeContextCurrent(window);
	glfwSetKeyCallback(window, key_callback);
	glfwSetWindowSizeCallback(window, window_size_callback);
	glfwSetMouseButtonCallback(window, put_angles);
	glClearColor(0, 0, 0, 0);
	project(width, height);
}

void display() {
	glColor3d(0, 100, 0);
	glClear(GL_COLOR_BUFFER_BIT);
	glBegin(GL_LINE_STRIP);
	for (Point p: polygon) {
		glVertex2d(p.x, p.y);
	}
	glEnd();
}

int main() {
	GLFWwindow* window;
	int width = WIDTH, height = HEIGHT;
	glfwSetErrorCallback(error_callback);
	if (!glfwInit()) {
		exit(EXIT_FAILURE);
	}
	window = glfwCreateWindow(width, height, "lab4", nullptr, nullptr);
	if (!window) {
		glfwTerminate();
		exit(EXIT_FAILURE);
	}
	init(window, width, height);
	while (!glfwWindowShouldClose(window)) {
		display();
		glfwSwapBuffers(window);
		glfwWaitEvents();
	}
	glfwDestroyWindow(window);
	glfwTerminate();
	exit(EXIT_SUCCESS);
}