import org.lwjgl.*;
import org.lwjgl.glfw.*;
import org.lwjgl.opengl.*;

import static org.lwjgl.glfw.GLFW.*;
import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.system.MemoryUtil.*;

public class HelloWorld {

    // The window handle
    private long window;

    public void run() {
        System.out.println("Hello LWJGL " + Version.getVersion() + "!");

        try {
            init();
            loop();

            // Destroy window and window callbacks
            glfwDestroyWindow(window);
        } finally {
            // Terminate GLFW and free the GLFWErrorCallback
            glfwTerminate();
        }
    }

    private void init() {
        // Setup an error callback. The default implementation
        // will print the error message in System.err.

        // Initialize GLFW. Most GLFW functions will not work before doing this.
        if ( glfwInit() != GLFW_TRUE )
            throw new IllegalStateException("Unable to initialize GLFW");

        // Configure our window
        glfwDefaultWindowHints(); // optional, the current window hints are already the default
        glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE); // the window will stay hidden after creation
        glfwWindowHint(GLFW_RESIZABLE, GLFW_TRUE); // the window will be resizable

        int WIDTH = 300;
        int HEIGHT = 300;

        // Create the window
        window = glfwCreateWindow(WIDTH, HEIGHT, "Hello World!", NULL, NULL);
        if ( window == NULL )
            throw new RuntimeException("Failed to create the GLFW window");

        // Get the resolution of the primary monitor
        GLFWVidMode vidmode = glfwGetVideoMode(glfwGetPrimaryMonitor());
        // Center our window
        glfwSetWindowPos(
                window,
                (vidmode.width() - WIDTH) / 2,
                (vidmode.height() - HEIGHT) / 2
        );

        // Make the OpenGL context current
        glfwMakeContextCurrent(window);
        // Enable v-sync
        glfwSwapInterval(1);

        // Make the window visible
        glfwShowWindow(window);
    }

    private void loop() {
        // This line is critical for LWJGL's interoperation with GLFW's
        // OpenGL context, or any context that is managed externally.
        // LWJGL detects the context that is current in the current thread,
        // creates the GLCapabilities instance and makes the OpenGL
        // bindings available for use.
        GL.createCapabilities();

        // Set the clear color
        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

        // Run the rendering loop until the user has attempted to close
        // the window or has pressed the ESCAPE key.
        while ( glfwWindowShouldClose(window) == GLFW_FALSE ) {
            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // clear the framebuffer

            glfwSwapBuffers(window); // swap the color buffers

            // Poll for window events. The key callback above will only be
            // invoked during this call.
            glfwPollEvents();
        }
    }

    public static void main(String[] args) {
        new HelloWorld().run();
    }

}
