/**
 * returns an RGBA buffer
 * @param {number} r red
 * @param {number} g green
 * @param {number} b blue
 * @param {number} a alpha
 * @returns {RGBA}
 */
function rgba(r, g, b, a) {
	const buffer = Uint8Array.allocPlain(4);
	buffer[0] = r;
	buffer[1] = g;
	buffer[2] = b;
	buffer[3] = a;
	return buffer;
}

const PAD_BUTTON_START = 0x1000;
const PAD_BUTTON_A = 0x0100;
const RED_COLOR = rgba(255, 0, 0, 255);
const GREEN_COLOR = rgba(0, 255, 0, 255);
const WHITE_COLOR = rgba(255, 255, 255, 255);
const FALLING_SPEED = 250;
const TERMINAL_VELOCITY_SPEED = 500;

function rgba_compare(rgba1, rgba2) {
	return (rgba1[0] == rgba2[0]) &&
		(rgba1[1] == rgba2[1]) &&
		(rgba1[2] == rgba2[2]) &&
		(rgba1[3] == rgba2[3]);
}

/**
 * clamps a number to the min and max values.
 * @param {number} num 
 * @param {number} min 
 * @param {number} max 
 * @returns a clamped number
 */
function clamp(num, min, max) {
	return Math.min(Math.max(num, min), max);
}

globalThis.rectangle_color = RED_COLOR;
/** @type {GRRLibTexture} */
globalThis.background = null;
/** @type {GRRLibTexture} */
globalThis.bird = null;

globalThis.bird_velocity = 0;
globalThis.bird_position = 0;

function swap_colors() {
	if (rgba_compare(rectangle_color, RED_COLOR)) {
		rectangle_color = GREEN_COLOR;
	} else if (rgba_compare(rectangle_color, GREEN_COLOR)) {
		rectangle_color = RED_COLOR;
	}
}

function start() {
	const background = wii.get_file("background-day.png");
	const bird = wii.get_file("yellowbird-midflap.png");

	globalThis.background = wii.grrlib.load_texture(background);
	globalThis.bird = wii.grrlib.load_texture(bird);
}

function update_bird() {
	const deltatime = wii.get_deltatime();
	bird_position -= bird_velocity * deltatime;
	bird_velocity = clamp(bird_velocity - (FALLING_SPEED * deltatime), -TERMINAL_VELOCITY_SPEED, TERMINAL_VELOCITY_SPEED);
	
	wii.grrlib.draw_img(0, bird_position, bird, 0, 1, 1, WHITE_COLOR);
}

function update() {
	const pressed = wii.pad.buttons_down();

	if (pressed & PAD_BUTTON_START) {
		wii.print("exiting from js");
		wii.exit();
	}

	if (pressed & PAD_BUTTON_A) {
		bird_velocity = FALLING_SPEED;
	}

	wii.grrlib.draw_img(0, 0, background, 0, 1, 1, WHITE_COLOR);
	update_bird();
	wii.print("deltatime: " + wii.get_deltatime())
}