Towers of Hanoi

TowersOfHanoi.js

'use strict';

var prompt = require('prompt');
prompt.start();

var stacks = {
    a: [4, 3, 2, 1],
    b: [],
    c: []
};

function printStacks() {
    console.log("a: " + stacks.a);
    console.log("b: " + stacks.b);
    console.log("c: " + stacks.c);
}

function movePiece(start, finish) {
    // "push" on the finish stack the block that is popped off the startig stack
    stacks[finish].push(stacks[start].pop());
}

function isLegal(start, finish) {
    // get the last indicies of your start and finish stacks
    var start_last_block_idx = stacks[start].length - 1
    var finish_last_block_idx = stacks[finish].length - 1

    // this will give us the block at the end of the start stack
    var movingBlock = stacks[start][start_last_block_idx];

    // if the finish stack is empty, this will be undefined, otherwise it will
    // give us the block at the last index of the finish stack
    var comparingBlock = stacks[finish][finish_last_block_idx];

    // compare the blocks
    if (movingBlock < comparingBlock || !comparingBlock) {
        // if the moving block is less than the block it's going to stack on
        // or if the finish stack is empty (hence the comparing block would be undefined)
        // remember '!' in front of a value will give the opposite "truthiness" value
        return true;
    }

    // otherwise return false. It is not a legal move
    console.log ("Not a Legal Move");
    return false;
}

function gameOver() {
    if (stacks['b'].length === 4 || stacks['c'].length === 4) {
        console.log('You Won!!!')
        return true;
    }
    return false;
}

function getPrompt() {
    printStacks();
    prompt.get(['start', 'finish'], function (error, result) {
        if (isLegal(result['start'], result['finish'])) {
            movePiece(result['start'], result['finish']);
        }

        if (!gameOver()) {
            getPrompt();
        }
    });
}

getPrompt();