var isArray = function(o) {
	return (o instanceof Array) || (Object.prototype.toString.apply(o) === "[object Array]");
},
combineApp = {
	combinations: function(args) {
		var n, inputArr = [], copyArr = [], results = [],
		subfunc = function(copies, prefix) {
			var i, j, myCopy = [], exprLen, currentChar = "", result = "";
			// if no prefix, set default to empty string
			if (typeof prefix === "undefined") {
				prefix = "";
			}
			// no copies, nothing to do... return
			if (!isArray(copies) || typeof copies[0] === "undefined") {
				return;
			}
			// remove first element from "copies" and store in "myCopy"
			myCopy = copies.splice(0, 1)[0];
			// store the number of characters to loop through
			exprLen = myCopy.length;
			for (i = 0; i < exprLen; i += 1) {
				currentChar = myCopy[i];
				result = prefix + currentChar;
				// if resulting string length is the number of characters of original string, we have a result
				if (result.length === n) {
					results.push(result);
				}
				// if there are copies left,
				//   pass remaining copies (by value) and result (as new prefix) into subfunc (recursively)
				if (typeof copies[0] !== "undefined") {
					subfunc(copies.slice(0), result);
				}
			}
		};
		// for each character in original string
		//   create array (inputArr) which contains original string (converted to array of char)
		if (typeof args.str === "string") {
			inputArr = args.str.split("");
			for (n = 0; n < inputArr.length; n += 1) {
				copyArr.push(inputArr.slice(0));
			}
		}
		if (isArray(args.arr)) {
			for (n = 0; n < args.arr.length; n += 1) {
				copyArr.push(args.arr[n].split(""));
			}
		}
		// pass copyArr into sub-function for recursion
		subfunc(copyArr);
		return results;
	},
	displayMsg: function(msgText, msgID) {
		var msg, nmsg;
		if (typeof msgID === "string" && document && document.getElementById && document.getElementById(msgID)) {
			msg = document.getElementById(msgID);
			nmsg = msg.cloneNode(false);
			msg.parentNode.insertBefore(nmsg, msg);
			msg.parentNode.removeChild(msg);
			nmsg.appendChild(document.createTextNode(msgText));
		} else if (msgText.length > 0) {
			alert(msgText);
		}
	},
	calcCombinations: function(args) {
		if (!args) {
			//args = {};
			return false;
		}
		args.src = (typeof args.src === "object") ? args.src : null;
		args.dest = (typeof args.dest === "object") ? args.dest : null;
		args.msgID = (typeof args.msgID === "string") ? args.msgID : null;
		args.tokenChar = (typeof args.tokenChar === "string") ? ((args.tokenChar.length > 0) ? args.tokenChar : ",") : ",";
		args.outputDelimiter = (typeof args.outputDelimiter === "string") ? args.outputDelimiter : ", ";
		args.maxCombinations = (typeof args.maxCombinations === "number") ? parseInt(args.maxCombinations, 10) : 600000;
		
		if (args.src === null || args.dest === null) {
			alert("calcCombinations() required arguments are missing.");
			return false;
		}
		var str = args.src.value, arr = [], objParam = {}, i, numChars, num = 0, doIt = true;
		args.dest.value = "";
		if (str.indexOf(args.tokenChar) !== -1) {
			arr = str.split(args.tokenChar);
			num = 1;
			for (i = 0; i < arr.length; i++) {
				numChars = arr[i].length;
				if (numChars === 0) {
					arr[i] = " ";
				} else {
					num *= numChars;
				}
			}
			str = "[" + arr.join("][") + "]";
			objParam = {"arr": arr};
		} else {
			num = Math.pow(str.length, str.length);
			objParam = {"str": str};
		}
		if (num <= args.maxCombinations && num > 5000) {
			doIt = confirm("This will produce " + num + " combinations. Are you sure you want to continue?");
		}
		if (num > 0) {
			if (num > args.maxCombinations) {
				args.dest.value = "It would take too long for JavaScript to calculate and display all of those combinations of characters.";
			}
			combineApp.displayMsg(num + " combinations of \"" + str + "\".", args.msgID);
			// don't kill the user's CPU using JavaScript to calculate too many combinations
			if (num <= args.maxCombinations && doIt) {
				args.dest.value = combineApp.combinations(objParam).join(args.outputDelimiter);
			}
		}
		return false;
	}
};