'use strict';

import Voronoi from './3rdparty/rhill-voronoi-core.js';

import { useAverage } from './modules/Util.js';
import { AABB, QuadTree } from './modules/Geometry.js';


/* from here on up, we always assume that points live in the range [(0,0), (1,1)) */

function lloydRelax(point_set, density) {
	/* setup quadtree and averages */
	let tree = new QuadTree(1,1);
	let averages = {};
	for (let i=0; i<point_set.length; i++) {
		const point = point_set[i];
		point.index = i;
		tree.insert(point);

		let [avg, append] = useAverage();
		const cent_x = { avg, append };
		[avg, append] = useAverage();
		const cent_y = { avg, append };
		averages[i] = { cent_x, cent_y };
	}

	/* compute average centroids */
	for (let x=0; x<1; x += 1/density) {
		for (let y=0; y<1; y += 1/density) {
			const point = { x, y };
			const closest = tree.closest(point);
			const { cent_x, cent_y } = averages[closest.index];
			cent_x.append(point.x);
			cent_y.append(point.y);
		}
	}

	/* return centroid points */
	const result = [];
	for (let i=0; i<point_set.length; i++) {
		const point = { x: averages[i].cent_x.avg(), y: averages[i].cent_y.avg() };
		result.push(point);
	}
	return result;
}


class Terrain {
	constructor() {
		const N_SEED_POINTS = 2**12;
		const N_RELAX_ITERATIONS = 1;
		const RELAX_DENSITY = 400;
		const randomPoint = () => ({x: Math.random(), y: Math.random()});

		this.min_height = 0;
		this.max_height = 0;

		let seed_points = [];
		for (let i=0; i<N_SEED_POINTS; i++) seed_points.push(randomPoint());

		for (let i=0; i<N_RELAX_ITERATIONS; i++)
			lloydRelax(seed_points, RELAX_DENSITY);

		const v = new Voronoi();
		this.graph = v.compute(seed_points, {xl: 0, xr: 1, yt: 0, yb: 1});

		this.tree = new QuadTree(1,1);
		for (let v of this.graph.vertices) {
			v.hue = 0;
			this.tree.insert(v);
		}
	}


	applyBrush(x, y, f, strength, radius) {
		const region = new AABB(x-radius, y-radius, 2*radius, 2*radius);
		const points = this.tree.root.getPointsInRegion(region);
		
		const dist2 = (a, b) => (a.x - b.x)**2 + (a.y - b.y)**2;

		const sigma = radius/3;
		const beta = 1/(2*sigma*sigma);
		const center = { x, y };
		const power = pt => Math.exp(-beta * dist2(pt, center));
		
		for (let pt of points) f(pt, strength * power(pt));
	}


	renderGrid(ct) {
		ct.save();
		ct.lineWidth = 0.001;
		for (let edge of this.graph.edges) {
			ct.fillStyle = `hsl(${edge.va.hue}, 100%, 50%)`;
			ct.beginPath();
			ct.arc(edge.va.x, edge.va.y, 0.005, 0, 2*Math.PI);
			ct.closePath();
			ct.fill();

			ct.beginPath();
			ct.moveTo(edge.va.x, edge.va.y);
			ct.lineTo(edge.vb.x, edge.vb.y);
			ct.closePath();
			ct.stroke();
		}
		ct.restore();
	}
}

export { lloydRelax };
export default Terrain;