const PAD_BUTTON_START = 0x1000;
const PAD_BUTTON_A = 0x0100;
const RED_COLOR = wii.rgba(255, 0, 0, 255);
const GREEN_COLOR = wii.rgba(0, 255, 0, 255);
const WHITE_COLOR = wii.rgba(255, 255, 255, 255);

const FALLING_SPEED = 250;
const TERMINAL_VELOCITY_SPEED = 500;
const PIPE_SPAWN_TIME = 4;
const PIPE_MAX_TIME = 5;

/**
 * throws if input is nullish.
 * @template T
 * @param {T | null | undefined} value
 * @returns {T}
 */
function nonNull(value) {
	if (value == null) {
		throw new Error("unexpected " + (value === null ? 'null' : 'undefined'))
	}
	return value
}

/**
 * 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);
}

/**
 * picks a random number between the min and max values.
 * @param {number} min 
 * @param {number} max 
 * @returns a random number
 */
function random_range(min, max) {
	const minCeiled = Math.ceil(min);
	const maxFloored = Math.floor(max);
	return Math.floor(Math.random() * (maxFloored - minCeiled) + minCeiled);
}

/** @type {GRRLibTexture | null} */
globalThis.background = null;

/** @type {{velocity: number, position: number, texture?: GRRLibTexture}} */
globalThis.bird = {
	velocity: 0,
	position: 0
};

/** @type {GRRLibTexture | null} */
globalThis.pipe = null;

/** @type {GRRLibTexture | null} */
globalThis.pipe_flipped = null;

/** @type {Pipe[]} */
globalThis.pipes = [];

/** @type {number} */
globalThis.timer = 0;

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

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

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, nonNull(bird.texture), 0, 1, 1, WHITE_COLOR);
}

function Pipe() {
	const top_max = 200;
	const top_y = random_range(0, top_max);

	wii.grrlib.draw_img(100, -top_y, nonNull(pipe_flipped), 0, 1, 1, WHITE_COLOR);
	wii.grrlib.draw_img(100, top_y + 400, nonNull(pipe), 0, 1, 1, WHITE_COLOR);

	this.top_y = -top_y
	this.bottom_y = -top_y + 400
	this.position = 650
	this.time_active = 0
}

Pipe.prototype.update = function () {
	if (this.time_active >= PIPE_MAX_TIME) {
		const index = pipes.indexOf(this);
		pipes.splice(index, -1);
		return;
	}
	wii.grrlib.draw_img(this.position, this.top_y, nonNull(pipe_flipped), 0, 1, 1, WHITE_COLOR);
	wii.grrlib.draw_img(this.position, this.bottom_y, nonNull(pipe), 0, 1, 1, WHITE_COLOR);
	this.position -= 100 * wii.get_deltatime();
	this.time_active += wii.get_deltatime();
}

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;
	}

	if (timer >= PIPE_SPAWN_TIME) {
		globalThis.timer = 0;
	}

	if (timer == 0) {
		pipes.push(new Pipe());
	}

	wii.grrlib.draw_img(0, 0, nonNull(background), 0, 1, 1, WHITE_COLOR);
	update_bird();
	for (var i = 0; i < pipes.length; i++) {
		pipes[i].update();
	}
	wii.print("deltatime: " + wii.get_deltatime())
	globalThis.timer += wii.get_deltatime();
}