import MapData from '../model/data/MapData';

import { loadSimpleEntity } from '../view/entity';
import DirectionHandler from '../view/input/DirectionHandler';
import { loadMap } from '../view/map';
import Renderer from '../view/renderer/Renderer';
import { SpriteView } from '../view/sprite';

import { getJSON } from '../util';

import { vec2 } from 'gl-matrix';

export class GameContext {
	public static async load(renderer: Renderer): Promise<GameContext> {
		const mapView = this.loadMap(renderer);
		const entity = loadSimpleEntity(renderer, 'simple_square');

		return new GameContext(
			renderer,
			await mapView,
			await entity,
		);
	}

	private static async loadMap(renderer: Renderer): Promise<SpriteView> {
		const map = new MapData(await getJSON('resources/map/test.json'));
		return loadMap(renderer, map);
	}

	private time: number|null = null;

	private readonly tick = 10; // ms per tick
	private readonly speed = 0.05; // movement per tick
	private readonly maxSkip = 20; // maximum ticks to process in a single render step

	private readonly input: DirectionHandler;

	private readonly entityPos: vec2 = vec2.create();
	private readonly entityMovement: vec2 = vec2.create();

	private constructor(
		private readonly renderer: Renderer,
		private readonly mapView: SpriteView,
		private readonly entity: SpriteView,
	) {
		this.input = new DirectionHandler();
		this.input.addListener((v) => {
			if (vec2.sqrLen(v) > 0)
				vec2.normalize(this.entityMovement, v);
			else
				vec2.copy(this.entityMovement, [0, 0]);
		});

		window.requestAnimationFrame(this.render);
	}

	private updateTime(time: number): number {
		const diff = this.time !== null ? time - this.time : 0;
		this.time = time;

		return diff;
	}

	private updateStep(): void {
		vec2.scaleAndAdd(this.entityPos, this.entityPos, this.entityMovement, this.speed);
	}

	private update(time: number): void {
		const diff = Math.min(this.maxSkip, this.updateTime(time));

		if (vec2.sqrLen(this.entityMovement) === 0) {
			this.renderer.snapToGrid(this.entityPos, this.entityPos);
			return;
		}

		for (let i = 0; i < diff; i++)
			this.updateStep();
	}

	private render = (time: number) => {
		this.update(Math.round(time / this.tick));

		this.renderer.setCenter(this.entityPos);
		this.renderer.clear();

		this.mapView.render();

		this.renderer.setTranslation(this.entityPos);
		this.entity.render();

		window.requestAnimationFrame(this.render);
	}
}