a-star/a-star.js

class Position
{
	constructor(x, y)
	{
		this.x = x;
		this.y = y;
	}

	getDistance(position, test)
	{
		return Math.sqrt(Math.pow(position.x - this.x, 2) + Math.pow(position.y - this.y, 2));
	}
}

class Node
{
	constructor(x, y)
	{
		this.position = new Position(x, y);
		this.g_cost = null;
		this.h_cost = null;
		this.f_cost = null;
		this.previous = null;
		this.isTraversable = true;
	}
}

class Map
{
	constructor(width, height)
	{
		this.width = width;
		this.height = height;
		this.nodes = [];
		this.startNode = null;
		this.targetNode = null;

		this._initialize();
	}

	_initialize()
	{
		for (let y = 0; y < this.height; y++) {
			let nodes = [];

			for (let x = 0; x < this.width; x++) {
				nodes.push(new Node(x, y));
			}

			this.nodes.push(nodes);
		}
	}

	getNodeAt(x, y)
	{
		return this.nodes[y][x];
	}

	getNeighbours(node, allowDiagonals = false)
	{
		let positions = [
			new Position(node.position.x - 1, node.position.y),
			new Position(node.position.x + 1, node.position.y),
			new Position(node.position.x, node.position.y - 1),
			new Position(node.position.x, node.position.y + 1),
		];

		if (allowDiagonals) {
			positions = positions.concat(
				[
					new Position(node.position.x - 1, node.position.y - 1),
					new Position(node.position.x + 1, node.position.y - 1),
					new Position(node.position.x - 1, node.position.y + 1),
					new Position(node.position.x + 1, node.position.y + 1),
				]
			);
		}

		const neighbours = [];

		for (const position of positions) {
			if (position.x < 0 || position.x >= this.width || position.y < 0 || position.y >= this.height) {
				continue;
			}

			neighbours.push(this.getNodeAt(position.x, position.y));
		}

		return neighbours;
	}

	draw(canvas, unitWidth, unitHeight) {
		canvas.width = this.width * unitWidth;
		canvas.height = this.height * unitHeight;

		const context = canvas.getContext('2d');

		for (let y = 0; y < this.height; y++) {
			for (let x = 0; x < this.width; x++) {
				this.drawNode(x, y, this.getNodeAt(x, y).isTraversable ? COLOR_GROUND : COLOR_WALL, canvas);
			}
		}
	}

	drawNode(x, y, color, canvas)
	{
		const context = canvas.getContext('2d');

		const unitWidth = canvas.width / this.width;
		const unitHeight = canvas.height / this.height;

		context.fillStyle = color;
		context.fillRect(x * unitWidth, y * unitHeight, unitWidth, unitHeight);
	}

	static loadFromLayout(layout)
	{
		const width = layout[0].length;
		const height = layout.length;

		const map = new Map(width, height);

		for (let y = 0; y < height; y++) {
			for (let x = 0; x < width; x++) {
				switch (layout[y].substr(x, 1)) {
					case '#':
						map.getNodeAt(x, y).isTraversable = false;
						break;

					case ' ':
						map.getNodeAt(x, y).isTraversable = true;
						break;

					case 'S':
						map.startNode = map.getNodeAt(x, y);
						map.startNode.isTraversable = true;
						break;

					case 'T':
						map.targetNode = map.getNodeAt(x, y);
						map.targetNode.isTraversable = true;
						break;
				}
			}
		}

		return map;
	}
}

class Pathfinder
{
	constructor(map)
	{
		this.map = map;
		this.open = [];
		this.closed = [];
		this.paths = {};
	}

	calculatePath(positionStart, positionTarget)
	{
		this.open.push(this.map.getNodeAt(positionStart.x, positionStart.y));

		let count = 0;

		while (this.open.length > 0) {
			count++;

			if (count > 1000) {
				alert('Path could not be calculated!');
				return;
			}

			let current = this._getCheapestNode(this.open);

			this._removeNodeFromOpen(current);
			this.closed.push(current);

			if (current.position.x === positionTarget.x && current.position.y === positionTarget.y) {
				break;
			}

			for (const neighbour of this.map.getNeighbours(current)) {
				if (!neighbour.isTraversable || this.closed.indexOf(neighbour) > -1) {
					continue;
				}

				const is_inside_open = this.open.indexOf(neighbour) > -1;

				const g_cost = neighbour.position.getDistance(positionStart) * 10;
				const h_cost = neighbour.position.getDistance(positionTarget) * 10;
				const f_cost = g_cost + h_cost;

				if (!is_inside_open) {
					neighbour.g_cost = g_cost;
					neighbour.h_cost = h_cost;
					neighbour.f_cost = f_cost;
					neighbour.previous = current;
				}

				if (!is_inside_open || current.position.getDistance(neighbour.position) < neighbour.position.getDistance(neighbour.previous.position)) {
					neighbour.f_cost = f_cost;
					neighbour.previous = current;

					if (!is_inside_open) {
						this.open.push(neighbour);
					}
				}
			}
		}
	}

	getPath(positionStart, positionTarget)
	{
		this.map.startNode = this.map.getNodeAt(positionStart.x, positionStart.y);
		this.map.targetNode = this.map.getNodeAt(positionTarget.x, positionTarget.y);

		let path = [];

		if (!this.map.getNodeAt(positionTarget.x, positionTarget.y).isTraversable) {
			return path;
		}

		this.calculatePath(positionStart, positionTarget);

		let targetNode = null;

		for (const node of this.closed) {
			if (node.position.x == positionTarget.x && node.position.y == positionTarget.y) {
				targetNode = node;
				break;
			}
		}

		let node = targetNode;

		while (node !== null) {
			path = [node].concat(path);

			node = node.previous;
		}

		return path;
	}

	reset()
	{
		this.open = [];
		this.closed = [];

		for (const node of this.map.nodes) {
			node.g_cost = null;
			node.h_cost = null;
			node.f_cost = null;
			node.previous = null;
		}

		this.map.startNode = null;
		this.map.targetNode = null;
	}

	_getCheapestNode(nodes)
	{
		let cheapest = nodes[0];

		for (const node of nodes) {
			if (node.f_cost < cheapest.f_cost || (node.f_cost == cheapest.f_cost && node.h_cost < cheapest.h_cost)) {
				cheapest = node;
			}
		}

		return cheapest;
	}

	_removeNodeFromOpen(node)
	{
		const index = this.open.indexOf(node);

		if (index === -1) {
			return;
		}

		this.open = this.open.slice(0, index).concat(this.open.slice(index + 1));
	}
}


class Player
{
	constructor(x, y)
	{
		this.x = x;
		this.y = y;
		this.speed = 0.5;
		this.color = '#ff0000';
	}

	draw(canvas, color = this.color)
	{
		const context = canvas.getContext('2d');

		const width = canvas.width / GRID_WIDTH;
		const height = canvas.height / GRID_HEIGHT;

		context.fillStyle = color;
		context.fillRect(this.x * GRID_WIDTH, this.y * GRID_HEIGHT, GRID_WIDTH, GRID_HEIGHT);
	}
}


function calculateRoute(start, target)
{
	const map = Map.loadFromLayout(layout);

	const canvas = document.getElementById('canvas');

	if (!map.getNodeAt(target.x, target.y).isTraversable) {
		return [];
	}

	map.draw(canvas, GRID_WIDTH, GRID_HEIGHT);

	const pathfinder = new Pathfinder(map);
	const path = pathfinder.getPath(start, target);

	/*
	for (const node of path) {
		map.drawNode(node.position.x, node.position.y, '#ffff00', canvas);
	}
	*/

	return path;
}


function movePlayerTo(player, x, y, canvas)
{
	const deltaX = x - player.x;
	const deltaY = y - player.y;

	player.draw(canvas, COLOR_GROUND);

	if (x !== player.x) {
		player.x += deltaX > 0 ? player.speed : -player.speed;

		if (deltaX < 0.1 && deltaX > -0.1) {
			player.x =  x;
		}
	}

	if (y !== player.y) {
		player.y += deltaY > 0 ? player.speed : -player.speed;

		if (deltaY < 0.1 && deltaY > -0.1) {
			player.y = y;
		}
	}

	player.draw(canvas);
}


function movePlayerRoute(player, route, canvas)
{
	let index = 1;

	const interval = setInterval(
		() => {
			movePlayerTo(player, route[index].position.x, route[index].position.y, canvas);

			if (route[index].position.x === player.x && route[index].position.y === player.y) {
				index++;
			}

			if (index === route.length) {
				clearInterval(interval);
				oldTarget = route[route.length - 1];
				isTargeting = false;
			}
		},
		20
	);
}


function update()
{
	map.draw(canvas, GRID_WIDTH, GRID_HEIGHT);
	player.draw(canvas);
}


const layout = [
	'      ##########################',
	'  S   #        # #         #   #',
	'      # ###### # # #######   # #',
	'      #      #   #       ##### #',
	'      # #### # # #######     # #',
	'      # #    # # #     ##### # #',
	'      # # #### # # ### #   # # #',
	'      # #      # #   # # # # # #',
	'      # ###### # ### # # # # # #',
	'             # #     # # #   # #',
	'###################### # ##### #',
	'#   #   #    #   #     # #      ',
	'# # # # # ## # # # ##### #      ',
	'# #   # #  #   # #     # #      ',
	'# ##### ## ##### ##### # #      ',
	'#     #    #   #       # #      ',
	'##### ###### # ######### #      ',
	'#            #           #      ',
	'##########################      '
];

const GRID_WIDTH = 40;
const GRID_HEIGHT = GRID_WIDTH;
const COLOR_WALL = '#aaaaaa';
const COLOR_GROUND = '#005500';

const map = Map.loadFromLayout(layout);
const canvas = document.getElementById('canvas');

let oldTarget = map.startNode.position;
let isTargeting = false;

const player = new Player(oldTarget.x, oldTarget.y);

canvas.addEventListener(
	'click',
	(event) => {
		if (isTargeting) {
			return;
		}

		isTargeting = true;

		const rect = canvas.getBoundingClientRect();

		const x = parseInt((event.clientX - rect.x) / GRID_WIDTH);
		const y = parseInt((event.clientY - rect.y) / GRID_HEIGHT);

		if (player.x === x && player.y === y) {
			isTargeting = false;
			return;
		}

		const target = new Position(x, y);

		const route = calculateRoute(new Position(player.x, player.y), new Position(x, y));

 		if (route.length > 1) {
			movePlayerRoute(player, route, canvas);
		} else {
			isTargeting = false;
		}
	}
);

const picker = document.getElementById('color-picker')
picker.value = player.color;

picker.addEventListener(
	'input',
	(event) => {
		player.color = event.target.value;
		update();
	}
);

update();