/**
 * Towers of hanoi
 * Nicholas Wright (www.nicholaswright.org/games/towers_of_hanoi)
 * Created 10 / 14 / 2006
 */
function TowersOfHanoi(intNumberOfDiscs) {
    this.objLeft = $('towers_of_hanoi_left');
    this.objPoleLeft = $('towers_of_hanoi_left_pole');
    this.objMiddle = $('towers_of_hanoi_middle');
    this.objPoleMiddle = $('towers_of_hanoi_middle_pole');
    this.objRight = $('towers_of_hanoi_right');
    this.objPoleRight = $('towers_of_hanoi_right_pole');
    this.objMoves = $('towers_of_hanoi_moves');
    this.objWins = $('towers_of_hanoi_wins');
    this.objPar = $('towers_of_hanoi_par');
    this.arrayObjects = [this.objLeft, this.objMiddle, this.objRight];
    this.intPoleWidth = 5;
    this.intPoleHeight = 283;
    this.intWins = 0;
    this.setNumberOfDiscs(intNumberOfDiscs);
    this.setPolePositions();
    this.resetGame();
}

TowersOfHanoi.prototype = {
    hashDraggableReferences: {},

    resetGame: function() {
        this.intMoves = 0;
        this.updateMoves();
        this.destroyAllDiscs();
        this.arrayDiscs = [[], [], []];
        this.createDiscs();
    },
    updatePar: function() {
        this.objPar.innerHTML = function(n) {
            if (n < 2) {
                return 1;
            } else {
                return n * arguments.callee(n - 1);
            }
        }(this.intNumberOfDiscs);
    },
    updateMoves: function() {
        this.objMoves.innerHTML = this.intMoves; 
    },
    updateWins: function() {
        this.objWins.innerHTML = this.intWins; 
    },
    setPolePositions: function() {
        var intColWidth = (Element.getDimensions(this.objLeft).width / 2);
        var arrayXY = Position.cumulativeOffset(this.objLeft);
        var arrayBoardXY = Position.cumulativeOffset(this.objLeft);

        this.objPoleLeft.style.left = ((arrayXY.first() + intColWidth) - (this.intPoleWidth / 2)) + "px";
        this.objPoleLeft.style.top = arrayXY.last() + "px";
        this.objPoleLeft.style.height = this.intPoleHeight +  "px";
        this.objPoleLeft.style.width = this.intPoleWidth +  "px";

        arrayXY = Position.cumulativeOffset(this.objMiddle);
        this.objPoleMiddle.style.left = ((arrayXY.first() + intColWidth) - (this.intPoleWidth / 2)) + "px";
        this.objPoleMiddle.style.top = arrayXY.last() + "px";
        this.objPoleMiddle.style.height = this.intPoleHeight +  "px";
        this.objPoleMiddle.style.width = this.intPoleWidth +  "px";

        arrayXY = Position.cumulativeOffset(this.objRight);
        this.objPoleRight.style.left = ((arrayXY.first() + intColWidth) - (this.intPoleWidth / 2)) + "px";
        this.objPoleRight.style.top = arrayXY.last() + "px";
        this.objPoleRight.style.height = this.intPoleHeight +  "px";
        this.objPoleRight.style.width = this.intPoleWidth +  "px";
    },
    setNumberOfDiscs: function(number_of_discs) {
        if ((number_of_discs >= 2) && (number_of_discs <= 9)) {
            this.intNumberOfDiscs = number_of_discs;
        } else {
            this.intNumberOfDiscs = 3;
        }
    },
    checkWin: function() {
        if (this.arrayDiscs.last().length >= this.intNumberOfDiscs) {
            if (this.intNumberOfDiscs >= 9) {
                alert("Wow, now that is impressive. Try again!");
            } else {
                alert("Congratulations! You won! Try the next level!");
                this.intNumberOfDiscs++;
            }
            this.intWins++;
            this.updateWins();
            this.resetGame();
            return true;
        }
        return false;
    },
    parseDiscSize: function(disc) {
        return disc.split("_").last();
    },
    createDiscs: function() {
        for (i = 0; i < this.intNumberOfDiscs; i++) {
            this.addDisc(0, "disc_" + i, (i == 0), true);
        }
    },
    addDisc: function(intStackNumber, strId, boolDraggable, boolInit) {
        var objTmpDiv = document.createElement("div");
        objTmpDiv.setAttribute("id", strId);
        objTmpDiv.style.width = (Number(this.parseDiscSize(strId) + "0") + 20) + "%";
        objTmpDiv.className = this.arrayObjects[intStackNumber].id;
        objTmpDiv.innerHTML = "&nbsp;";
        if (boolInit) {
            this.arrayObjects[intStackNumber].appendChild(objTmpDiv);
            this.arrayDiscs[intStackNumber].push(strId);
        } else {
            this.arrayObjects[intStackNumber].insertBefore(objTmpDiv, this.arrayObjects[intStackNumber].firstChild);
            this.arrayDiscs[intStackNumber].unshift(strId);
        }
        if (boolDraggable) {
            this.addDraggable(strId);
        }
    },
    removeDisc: function(intStackNumber, strId) {
        this.destroyDraggable(this.arrayDiscs[intStackNumber].first());
        Element.remove(strId);
        this.arrayDiscs[intStackNumber].shift();
        if (this.arrayDiscs[intStackNumber].length > 0) {
            this.addDraggable(this.arrayDiscs[intStackNumber].first());
        }
    },
    addDraggable: function(strId) {
        this.hashDraggableReferences[strId] = new Draggable(strId, {revert: true});
    },
    destroyDraggable: function(strId) {
        if (this.hashDraggableReferences[strId]) {
            this.hashDraggableReferences[strId].destroy();
            delete this.hashDraggableReferences[strId];
        }
    },
    destroyAllDiscs: function() {
        for (var i = 0; i < this.arrayObjects.length; i++) {
            while (this.arrayObjects[i].hasChildNodes()) {
                this.arrayObjects[i].removeChild(this.arrayObjects[i].firstChild);
            }
        }
        for (j in this.hashDraggableReferences) {
            this.destroyDraggable(j);
        }
    },
    moveSmallerDisc: function(objElement, intStackNumber) {
        if ((this.arrayDiscs[intStackNumber].length == 0) ||
            (this.parseDiscSize(this.arrayDiscs[intStackNumber].first()) > this.parseDiscSize(objElement.id))) {
            this.removeDisc(this.findPreviousStack(objElement.id, intStackNumber), objElement.id);
            this.destroyDraggable(this.arrayDiscs[intStackNumber].first());
            this.addDisc(intStackNumber, objElement.id, true);
            this.intMoves++;
            this.updateMoves();
            this.checkWin();
            return true;
        }
        return false;
    },
    findPreviousStack: function(strId, intStackNumber) {
        for (var i = 0; i < this.arrayDiscs.length; i++) {
            if ((i != intStackNumber) && ($A(this.arrayDiscs[i]).include(strId))) {
                return i;
            }
        }
    },
    pushOntoLeft: function(objElement) {
        this.moveSmallerDisc(objElement, 0);
    },
    pushOntoMiddle: function(objElement) {
        this.moveSmallerDisc(objElement, 1);
    },
    pushOntoRight: function(objElement) {
        this.moveSmallerDisc(objElement, 2);
    }
};

Objective
Move all of the discs from the left column to the column on the far right in as few moves as possible.

Instructions
Click down on a disc and hold it to drag it to another column. Repeat this proccess, adhering to the rules, until you complete the level. Upon completing a level you will be promptly taken to the next level.

Your par count lets you know the lowest possible number of moves needed to complete the level.

You may also retry the current level at any time by clicking the "retry level" link.