(function (root, factory) {
	if (typeof define === 'function' && define.amd) {
		// AMD. Register as an anonymous module.
		define([], factory);
	} else if (typeof exports === 'object') {
		// Node. Does not work with strict CommonJS, but
		// only CommonJS-like environments that support module.exports,
		// like Node.
		module.exports = factory();
	} else {
		// Browser globals (root is window)
		root.StringMask = factory();
	}
}(this, function () {
	var tokens = {
		'0': {pattern: /\d/, _default: '0'},
		'9': {pattern: /\d/, optional: true},
		'#': {pattern: /\d/, optional: true, recursive: true},
		'S': {pattern: /[a-zA-Z]/},
		'U': {pattern: /[a-zA-Z]/, transform: function (c) { return c.toLocaleUpperCase(); }},
		'L': {pattern: /[a-zA-Z]/, transform: function (c) { return c.toLocaleLowerCase(); }},
		'$': {escape: true}
	};

	function isEscaped(pattern, pos) {
		var count = 0;
		var i = pos - 1;
		var token = {escape: true};
		while (i >= 0 && token && token.escape) {
			token = tokens[pattern.charAt(i)];
			count += token && token.escape ? 1 : 0;
			i--;
		}
		return count > 0 && count%2 === 1;
	}

	function calcOptionalNumbersToUse(pattern, value) {
		var numbersInP = pattern.replace(/[^0]/g,'').length;
		var numbersInV = value.replace(/[^\d]/g,'').length;
		return numbersInV - numbersInP;
	}

	function concatChar(text, character, options, token) {
		if (token && typeof token.transform === 'function') character = token.transform(character);
		if (options.reverse) return character + text;
		return text + character;
	}

	function hasMoreTokens(pattern, pos, inc) {
		var pc = pattern.charAt(pos);
		var token = tokens[pc];
		if (pc === '') return false;
		return token && !token.escape ? true : hasMoreTokens(pattern, pos + inc, inc);
	}

	function insertChar(text, char, position) {
		var t = text.split('');
		t.splice(position >= 0 ? position: 0, 0, char);
		return t.join('');
	}

	function StringMask(pattern, opt) {
		this.options = opt || {};
		this.options = {
			reverse: this.options.reverse || false,
			usedefaults: this.options.usedefaults || this.options.reverse
		};
		this.pattern = pattern;
	}

	StringMask.prototype.process = function proccess(value) {
		if (!value) {
			return {result: '', valid: false};
		}
		value = value + '';
		var pattern2 = this.pattern;
		var valid = true;
		var formatted = '';
		var valuePos = this.options.reverse ? value.length - 1 : 0;
		var optionalNumbersToUse = calcOptionalNumbersToUse(pattern2, value);
		var escapeNext = false;
		var recursive = [];
		var inRecursiveMode = false;

		var steps = {
			start: this.options.reverse ? pattern2.length - 1 : 0,
			end: this.options.reverse ? -1 : pattern2.length,
			inc: this.options.reverse ? -1 : 1
		};

		function continueCondition(options) {
			if (!inRecursiveMode && hasMoreTokens(pattern2, i, steps.inc)) {
				return true;
			} else if (!inRecursiveMode) {
				inRecursiveMode = recursive.length > 0;
			}

			if (inRecursiveMode) {
				var pc = recursive.shift();
				recursive.push(pc);
				if (options.reverse && valuePos >= 0) {
					i++;
					pattern2 = insertChar(pattern2, pc, i);
					return true;
				} else if (!options.reverse && valuePos < value.length) {
					pattern2 = insertChar(pattern2, pc, i);
					return true;
				}
			}
			return i < pattern2.length && i >= 0;
		}

		for (var i = steps.start; continueCondition(this.options); i = i + steps.inc) {
			var pc = pattern2.charAt(i);
			var vc = value.charAt(valuePos);
			var token = tokens[pc];
			if (!inRecursiveMode || vc) {
				if (this.options.reverse && isEscaped(pattern2, i)) {
					formatted = concatChar(formatted, pc, this.options, token);
					i = i + steps.inc;
					continue;
				} else if (!this.options.reverse && escapeNext) {
					formatted = concatChar(formatted, pc, this.options, token);
					escapeNext = false;
					continue;
				} else if (!this.options.reverse && token && token.escape) {
					escapeNext = true;
					continue;
				}
			}

			if (!inRecursiveMode && token && token.recursive) {
				recursive.push(pc);
			} else if (inRecursiveMode && !vc) {
				if (!token || !token.recursive) formatted = concatChar(formatted, pc, this.options, token);
				continue;
			} else if (recursive.length > 0 && token && !token.recursive) {
				// Recursive tokens most be the last tokens of the pattern
				valid = false;
				continue;
			} else if (!inRecursiveMode && recursive.length > 0 && !vc) {
				continue;
			}

			if (!token) {
				formatted = concatChar(formatted, pc, this.options, token);
				if (!inRecursiveMode && recursive.length) {
					recursive.push(pc);
				}
			} else if (token.optional) {
				if (token.pattern.test(vc) && optionalNumbersToUse) {
					formatted = concatChar(formatted, vc, this.options, token);
					valuePos = valuePos + steps.inc;
					optionalNumbersToUse--;
				} else if (recursive.length > 0 && vc) {
					valid = false;
					break;
				}
			} else if (token.pattern.test(vc)) {
				formatted = concatChar(formatted, vc, this.options, token);
				valuePos = valuePos + steps.inc;
			} else if (!vc && token._default && this.options.usedefaults) {
				formatted = concatChar(formatted, token._default, this.options, token);
			} else {
				valid = false;
				break;
			}
		}

		return {result: formatted, valid: valid};
	};

	StringMask.prototype.apply = function(value) {
		return this.process(value).result;
	};

	StringMask.prototype.validate = function(value) {
		return this.process(value).valid;
	};

	StringMask.process = function(value, pattern, options) {
		return new StringMask(pattern, options).process(value);
	};

	StringMask.apply = function(value, pattern, options) {
		return new StringMask(pattern, options).apply(value);
	};

	StringMask.validate = function(value, pattern, options) {
		return new StringMask(pattern, options).validate(value);
	};

	return StringMask;
}));