const x_dim = 800;
const y_dim = 600;

class Gates {
	constructor() {
		this.x = 200;
		this.y = 40;
		this.v_x = 0;
		this.v_y = 0;
		this.a_x = 0;
		this.a_y = 0;
		this.target_x = 200;
		this.target_y = 40;
		this.health = 1;
	}

	radius() {
		return 30;
	}

	choose_position() {
		const [x, y] = random_position();
		this.target_x = x;
		this.target_y = y;
	}

	act(count) {
		const max_accel = (1 - this.health) * 0.75 + 0.25;
		const max_velocity = (1 - this.health) * 5 + 5;
		let dx = this.target_x - this.x;
		let dy = this.target_y - this.y;
		/* If we've arrived (close and stopped) */
		if (Math.sqrt(dx * dx + dy * dy) < max_velocity / max_accel && Math.sqrt(this.v_x * this.v_x + this.v_y * this.v_y) < 0.01) {
			/* Then pick a new target */
			this.choose_position();

		}

		dx = this.target_x - this.x;
		dy = this.target_y - this.y;
		/* if we're close */
		if (Math.sqrt(dx * dx + dy * dy) < max_velocity / max_accel) {
			/* Then slow down */
			const [x, y] = shorten(-this.v_x, -this.v_y, max_accel);
			this.a_x = x;
			this.a_y = y;
		} else {
			/* Otherwise, speed up */
			const [x, y] = shorten(dx, dy, max_accel);
			this.a_x = x;
			this.a_y = y;
		}

		/* If we're going too fast */
		if (Math.sqrt(this.v_x * this.v_x + this.v_y * this.v_y) > max_velocity) {
			/* Then don't go faster */
			if (Math.sign(this.v_x) == Math.sign(this.a_x)) {
				this.a_x = 0;
			}
			if (Math.sign(this.v_y) == Math.sign(this.a_y)) {
				this.a_y = 0;
			}
		}

		this.v_x += this.a_x;
		this.x += this.v_x;
		this.v_y += this.a_y;
		this.y += this.v_y;
		if (count % 20 === 0) {
			let num_bullets;
			if (this.health >= 0.8) {
				num_bullets = 5;
			} else if (this.health >= 0.7) {
				num_bullets = 6;
			} else if (this.health >= 0.5) {
				num_bullets = 7;
			} else if (this.health >= 0.4) {
				num_bullets = 8;
			} else if (this.health >= 0.3) {
				num_bullets = 9;
			} else if (this.health >= 0.2) {
				num_bullets = 10;
			} else {
				num_bullets = 11;
			}
			const result = [];
			for (let i = 0; i < num_bullets; i++) {
				result.push(random_bullet(this));
			}
			return result;
		} else {
			return [];
		}
	}

	injure(damage) {
		this.health -= damage;
	}

	center() {
		return [16, 23];
	}
}

class GatesBullet {
	constructor(x, d_x, y, d_y) {
		this.x = x;
		this.y = y;
		this.d_x = d_x;
		this.d_y = d_y;
	}

	radius() {
		return 10;
	}

	center() {
		return [20, 20];
	}
}

function random_position() {
	return [
		Math.random() * (x_dim - 200) + 100,
		Math.random() * 100,
	];
}

function random_bullet(enemy) {
	const multiplier = 2 + 3 * (1 - enemy.health);
	const theta = Math.random() * 2 * Math.PI / 3 + Math.PI / 6;
	const dx = Math.cos(theta) * multiplier;
	const dy = Math.sin(theta) * multiplier;
	return new GatesBullet(enemy.x, dx, enemy.y, dy);
}

function shorten(x, y, maxlen) {
	const len = Math.sqrt(x * x + y * y);
	if (len > maxlen) {
		return [x / len / 2, y / len / 2];
	} else {
		return [x, y];
	}
}

class Player {
	constructor() {
		this.x = 400;
		this.y = 500;
		this.x_d = 0;
		this.y_d = 0;
		this.down_p = false;
		this.left_p = false;
		this.right_p = false;
		this.up_p = false;
		this.fire_rate = 15;
		this.shift_p = false;
	}

	act(events) {
		for (const event of events) {
			const [kind, key] = event;
			if (kind === 'keydown' && key === 'ArrowDown') {
				this.down_p = true;
				this.y_d = -1;
			} else if (kind === 'keyup' && key === 'ArrowDown') {
				this.down_p = false;
			} else if (kind === 'keydown' && key === 'ArrowUp') {
				this.up_p = true;
				this.y_d = 1;
			} else if (kind === 'keyup' && key === 'ArrowUp') {
				this.up_p = false;
			} else if (kind === 'keydown' && key === 'ArrowLeft') {
				this.left_p = true;
				this.x_d = -1;
			} else if (kind === 'keyup' && key === 'ArrowLeft') {
				this.left_p = false;
			} else if (kind === 'keydown' && key === 'ArrowRight') {
				this.right_p = true;
				this.x_d = 1;
			} else if (kind === 'keyup' && key === 'ArrowRight') {
				this.right_p = false;
			} else if (kind === 'keydown' && key === 'Shift') {
				this.shift_p = true;
			} else if (kind === 'keyup' && key === 'Shift') {
				this.shift_p = false;
			}
		}
		if (this.left_p) {
			if (!this.right_p) {
				this.x_d = -1;
			}
		} else if (this.right_p) {
			this.x_d = 1;
		} else {
			this.x_d = 0;
		}
		if (this.up_p) {
			if (!this.down_p) {
				this.y_d = -1;
			}
		} else if (this.down_p) {
			this.y_d = 1;
		} else {
			this.y_d = 0;
		}
		/* Don't go off the side */
		if (this.x_d < 0 && this.x <= 0 || this.x >= x_dim && this.x_d > 0) {
			this.x_d = 0;
		}
		if (this.y <= 0 && this.y_d < 0 || this.y >= y_dim && this.y_d > 0) {
			this.y_d = 0;
		}

		if (this.shift_p) {
			this.x += this.x_d;
			this.y += this.y_d;
		} else {
			this.x += this.x_d * 3;
			this.y += this.y_d * 3;
		}
	}

	radius() {
		return 3;
	}

	center() {
		return [33, 21];
	}
}

function straight_bullet_act(straight_bullet) {
	const x = straight_bullet.x;
	const d_x = straight_bullet.d_x;
	straight_bullet.x += d_x;
	const y = straight_bullet.y;
	const d_y = straight_bullet.d_y;
	straight_bullet.y += d_y;
}

function straight_bullet_delete(straight_bullet) {
	straight_bullet.x = -1000; // LMAO
}

class PBullet {
	constructor(x, d_x, y, d_y) {
		this.x = x;
		this.y = y;
		this.d_x = d_x;
		this.d_y = d_y;
	}

	damage() {
		return 0.01
	}

	radius() {
		return 10;
	}

	center() {
		return [16, 22];
	}
}

class State {
	constructor() {
		this.player = new Player();
		this.enemies = [new Gates()];
		this.bullets = [];
		this.count = 0;
		this.player_bullets = [];
	}
}

function dist(x1, y1, x2, y2) {
	const xdist = x1 - x2;
	const ydist = y1 - y2;
	return Math.sqrt(xdist * xdist + ydist * ydist);
}

function overlaps(self, other) {
	const sx = self.x;
	const ox = other.x;
	const sy = self.y;
	const oy = other.y;
	const threshold = self.radius() + other.radius();
	if (Math.abs(sx - ox) >= threshold || Math.abs(sy - oy) >= threshold) {
		return false;
	}
	const d = dist(sx, sy, ox, oy);
	return d < threshold;
}

function outside(positioned) {
	const x = positioned.x;
	const y = positioned.y;
	return x < -100
		|| x > x_dim + 100
		|| y < -100
		|| y > y_dim + 100;
}

function draw(positioned, ctx, bitmap) {
	const [cx, cy] = positioned.center();
	const x0 = Math.round(positioned.x) - cx;
	const y0 = Math.round(positioned.y) - cy;
	ctx.drawImage(bitmap, x0, y0);
}

let events = [];

window.addEventListener('keydown', (e) => events.push(['keydown', e.key]));
window.addEventListener('keyup', (e) => events.push(['keyup', e.key]));

const duration = 1000 / 60;

function frame(ctx, st, events, textures) {
	const new_bullets = [];
	const count = st.count;
	for (const enemy of st.enemies) {
		new_bullets.push(...enemy.act(count));
	}
	for (const bullet of st.bullets) {
		straight_bullet_act(bullet);
	}
	for (const bullet of st.player_bullets) {
		straight_bullet_act(bullet);
	}
	st.player.act(events);
	if (count % st.player.fire_rate === 0) {
		st.player_bullets.push(new PBullet(st.player.x, 0, st.player.y, -3.5));
	}
	for (const bullet of st.bullets) {
		if (overlaps(st.player, bullet)) {
			return 'loss';
		}
	}
	for (const bullet of new_bullets) {
		if (overlaps(st.player, bullet)) {
			return 'loss';
		}
	}
	for (const enemy of st.enemies) {
		for (const bullet of st.player_bullets) {
			if (overlaps(enemy, bullet)) {
				enemy.injure(bullet.damage());
				straight_bullet_delete(bullet);
			}
		}
	}
	st.enemies = st.enemies.filter((enemy) => enemy.health > 0);
	if (st.enemies.length === 0) {
		return 'win';
	}
	st.bullets = st.bullets.filter((bullet) => !outside(bullet));
	st.bullets.push(...new_bullets);
	st.player_bullets = st.player_bullets.filter((bullet) => !outside(bullet));

	for (const bullet of st.player_bullets) {
		draw(bullet, ctx, textures.pbullet);
	}
	for (const enemy of st.enemies) {
		draw(enemy, ctx, textures.enemy);
	}
	draw(st.player, ctx, textures.player);
	for (const bullet of st.bullets) {
		draw(bullet, ctx, textures.ebullet);
	}
	ctx.strokeStyle = "red";
	ctx.strokeRect(0, 0, Math.round(st.enemies[0].health * x_dim), 20);
	st.count++;
	return 'nothing';
}

const sprite_sheet = document.getElementById('sprite-sheet');

async function get_bitmap(off, w, h) {
	await sprite_sheet.decode();
	return await window.createImageBitmap(sprite_sheet, off, 0, w, h);
}

async function get_player_bitmap() {
	return get_bitmap(1707, 61, 46);
}

async function get_enemy_bitmap() {
	return get_bitmap(38, 32, 40);
}

async function get_ebullet_bitmap() {
	return get_bitmap(0, 37, 39);
}

async function get_pbullet_bitmap() {
	return get_bitmap(1673, 33, 40);
}

async function generic_message(ctx, image, okay) {
	const bitmap = await get_bitmap(image, 800, 600);
	await new Promise((resolve) => {
		const loop = () => {
			const ev = events;
			events = [];
			for (const event of ev) {
				const [type, keycode] = event;
				if (type === 'keydown' && keycode === okay) {
					resolve();
					return;
				}
			}
			ctx.drawImage(bitmap, 0, 0);
			window.requestAnimationFrame(loop);
		};
		window.requestAnimationFrame(loop);
	});
}

async function introduction(ctx) {
	await generic_message(ctx, 71, 'Enter');
}

async function loss(ctx) {
	await generic_message(ctx, 872, 'r');
}

async function victory(ctx) {
	await generic_message(ctx, 1769, 'r');
}

async function main() {
	const canvas = document.getElementById('canvas');
	const ctx = canvas.getContext('2d');

	await introduction(ctx);

	while (true) {
		const st = new State();
		const [
			player_bitmap,
			enemy_bitmap,
			ebullet_bitmap,
			pbullet_bitmap,
		] = await Promise.all([
			get_player_bitmap(),
			get_enemy_bitmap(),
			get_ebullet_bitmap(),
			get_pbullet_bitmap(),
		]);
		const textures = {
			player: player_bitmap,
			enemy: enemy_bitmap,
			ebullet: ebullet_bitmap,
			pbullet: pbullet_bitmap,
		};
		let last_frame_time = null;
		let accumulator = 0;
		const result = await new Promise((resolve) => {
			const loop = (now) => {
				if (last_frame_time !== null) {
					accumulator += now - last_frame_time;
				}
				last_frame_time = now;

				while (accumulator >= duration) {
					accumulator -= duration;

					ctx.fillStyle = "white";
					ctx.fillRect(0, 0, x_dim, y_dim);
					const result = frame(ctx, st, events, textures);
					events = [];
					if (result === 'loss' || result === 'win') {
						resolve(result);
						return;
					}
				}
				window.requestAnimationFrame(loop);
			};
			window.requestAnimationFrame(loop);
		});
		if (result === 'loss') {
			await loss(ctx);
		} else if (result === 'win') {
			await victory(ctx);
		}
	}
}

main()