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/**
* A* (A-Star) Pathfinding Algorithm in JavaScript
* @author  Matthew Trost
* @license Creative Commons Attribution-ShareAlike 3.0 Unported License
* @datepublished December 2010
*/

function astar (map, heuristic, cutCorners) {
	var listOpen = [];
	var listClosed = [];
	var listPath = [];
	var nodeGoal = createTerminalNode(map, heuristic, "g", null);
	var nodeStart = createTerminalNode(map, heuristic, "s", nodeGoal);
	addNodeToList(nodeStart, listOpen);
	
	var n;
	while (!isListEmpty(listOpen)) {
		n = returnNodeWithLowestFScore(listOpen);
		addNodeToList(n, listClosed);
		removeNodeFromList(n, listOpen);
		if (areNodesEqual(n, nodeGoal)) {
			pathTo(n, listPath);
			listPath.reverse();
			return listPath;
		}
		n.makeChildNodes(map, heuristic, cutCorners, nodeGoal);
		cullUnwantedNodes(n.childNodes, listOpen);
		cullUnwantedNodes(n.childNodes, listClosed);
		removeMatchingNodes(n.childNodes, listOpen);
		removeMatchingNodes(n.childNodes, listClosed);
		addListToList(n.childNodes, listOpen);
	}
	return null;
}

function pathTo (n, listPath) {
	listPath.push(new NodeCoordinate(n.row, n.col));
	if (n.parentNode == null)
		return;
	pathTo(n.parentNode, listPath);
}

function addListToList(listA, listB) {
	for (x in listA)
		listB.push(listA[x]);
}

function removeMatchingNodes (listToCheck, listToClean) {
	var listToCheckLength = listToCheck.length;
	for (var i = 0; i < listToCheckLength; i++) {
		for (var j = 0; j < listToClean.length; j++) {
			if (listToClean[j].row == listToCheck[i].row && listToClean[j].col == listToCheck[i].col)
				listToClean.splice(j, 1);
		}
	}
}

function cullUnwantedNodes (listToCull, listToCompare) {
	var listToCompareLength = listToCompare.length;
	for (var i = 0; i < listToCompareLength; i++) {
		for (var j = 0; j < listToCull.length; j++) {
			if (listToCull[j].row == listToCompare[i].row && listToCull[j].col == listToCompare[i].col) {
				if (listToCull[j].f >= listToCompare[i].f)
					listToCull.splice(j, 1);
			}
		}
	}
}

function areNodesEqual (nodeA, nodeB) {
	if (nodeA.row == nodeB.row && nodeA.col == nodeB.col)
		return true;
	else
		return false;
}

function returnNodeWithLowestFScore (list) {
	var lowestNode = list[0];
	for (x in list)
		lowestNode = (list[x].f < lowestNode.f) ? list[x] : lowestNode;
	return lowestNode;
}

function isListEmpty (list) {
	return (list.length < 1) ? true : false;
}

function removeNodeFromList (node, list) {
	var listLength = list.length;
	for (var i = 0; i < listLength; i++) {
		if (node.row == list[i].row && node.col == list[i].col) {
			list.splice(i, 1);
			break;
		}
	}
}

function addNodeToList (node, list) {
	list.push(node);
}

function createTerminalNode (map, heuristic, nodeType, nodeGoal) {
	var mapRows = map.length;
	var mapCols = map[0].length;
	for (var row = 0; row < mapRows; row++) {
		for (var col = 0; col < mapCols; col++) {
			if (map[row][col] == nodeType) {
				return new Node(row, col, map, heuristic, null, nodeGoal);
			}
		}
	}
	return null;
}

function returnHScore (node, heuristic, nodeGoal) {
	var y = Math.abs(node.row - nodeGoal.row);
	var x = Math.abs(node.col - nodeGoal.col);
	switch (heuristic) {
		case "manhattan":
			return (y + x) * 10;
		case "diagonal":
			return (x > y) ? (y * 14) + 10 * (x - y) : (x * 14) + 10 * (y - x);
		case "euclidean":
			return Math.sqrt((x * x) + (y * y));
		default:
			return null;
	}
}

function NodeCoordinate (row, col) {
	this.row = row;
	this.col = col;
}

function Node (row, col, map, heuristic, parentNode, nodeGoal) {
	var mapLength = map.length;
	var mapRowLength = map[0].length;
	this.row = row;
	this.col = col;
	this.northAmbit = (row == 0) ? 0 : row - 1;
	this.southAmbit = (row == mapLength - 1) ? mapLength - 1 : row + 1;
	this.westAmbit = (col == 0) ? 0 : col - 1;
	this.eastAmbit = (col == mapRowLength - 1) ? mapRowLength - 1 : col + 1;
	this.parentNode = parentNode;
	this.childNodes = [];

	if (parentNode != null) {
		if (row == parentNode.row || col == parentNode.col)
			this.g = parentNode.g + 10;
		else
			this.g = parentNode.g + 14;
		this.h = returnHScore(this, heuristic, nodeGoal);
	}
	else {
		this.g = 0;
		if (map[row][col] == "s")
			this.h = returnHScore(this, heuristic, nodeGoal);
		else
			this.h = 0;
	}
	this.f = this.g + this.h;
	
	this.makeChildNodes = function (map, heuristic, cutCorners, nodeGoal) {
		for (var i = this.northAmbit; i <= this.southAmbit; i++) {
			for (var j = this.westAmbit; j <= this.eastAmbit; j++) {
				if (i != this.row || j != this.col) {
					if (map[i][j] != "u") {
						if (cutCorners == true) 
							this.childNodes.push(new Node(i, j, map, heuristic, this, nodeGoal));
						else {
							if (i == this.row || j == this.col)
								this.childNodes.push(new Node(i, j, map, heuristic, this, nodeGoal));	
						}
					}
				}
			}
		}
	}
}