import structures from "./structures.js";

export default class Level {
	constructor(canvas) {
		this.canvas = canvas;
		this.ctx = canvas.getContext("2d");
		this.lastTime = null;
		this.raf = null;
		this.minPhysFPS = 20;
		this.minFPS = 5;
		this.backgroundColor = "#87CEFA";

		this.entities = [];
		this.colliders = [];

		this.structures = [];

		this.evts = [];
	}

	spawnEntity(ent, x, y) {
		ent.bounds.pos.set(x, y);

		this.entities.push(ent);
		if (ent.has("collider"))
			this.colliders.push(ent);

		ent._init();
	}

	spawnStructure(structure, x, y) {
		structure.bounds.pos.set(x, y);
		this.structures.push(structure);
		structure.init();
	}

	physics(dt) {
		this.entities.forEach(ent =>
			ent._update(dt));
		this.entities.forEach(ent =>
			ent._postUpdate(dt));

		// Collide with structures
		this.structures.forEach(s => {
			if (!s.attrs.wall && !s.attrs.platform)
				return;

			this.colliders.forEach(ent => {
				let bounds = s.collidesWith(ent.bounds);
				if (!bounds)
					return;

				ent.t.collider.collideStructure(s, bounds);
			});
		});

		// Collide with entities
		this.colliders.forEach(ent => {
			this.colliders.forEach(ent2 => {
				if (ent === ent2 || !ent.bounds.intersects(ent2.bounds))
					return;

				ent.t.collider.collideEntity(ent2);
			});
		});
	}

	draw() {
		this.ctx.resetTransform();
		this.ctx.beginPath();
		this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height);

		this.entities.forEach(ent => ent.draw(this.ctx));
		this.structures.forEach(struct => struct.draw(this.ctx));
	}

	update(time) {
		if (this.lastTime != null) {
			let dt = (time - this.lastTime) / 1000;

			if (1 / dt < this.minFPS) {
				console.log(
					"Too long between updates ("+dt.toFixed(2)+"s, "+
					(1 / dt).toFixed(2)+"FPS). Skipping.");
			} else {

				// We accept really low FPSes,
				// but if the FPS gets too low, we want to run multiple
				// physics steps in the frame.
				let physdt = dt;
				let nSteps = 1;
				while (1 / physdt < this.minPhysFPS) {
					physdt /= 2;
					nSteps *= 2;
				}

				if (nSteps > 1) {
					console.log(
						"Too long between frames for physics ("+dt.toFixed(2)+"s). "+
						"Running "+nSteps+" simulations ("+physdt.toFixed(2)+"s) in one frame.");
				}

				for (let i = 0; i < nSteps; ++i)
					this.physics(physdt);
			}

			this.draw();
		}

		this.lastTime = time;
		this.raf = requestAnimationFrame(this.update.bind(this));
	}

	start() {
		this.canvas.style.background = this.backgroundColor;
		if (this.raf == null) {
			this.lastTime = null;
			this.update();
			console.log("Started.");
		}
	}

	stop() {
		if (this.raf != null) {
			cancelAnimationFrame(this.raf);
			this.raf = null;
			console.log("Stopped.");
		}
	}
}