/**
 * @fileoverview Base for helper functions and other globals.
 * @author mking@mking.me (Matt King)
 */

/**
 * Used globally to determine if functionality should be
 * degraded for older browsers. Currently applies to IE7 and older.
 */
var degraded = false;

if (typeof String.prototype.trim !== 'function') {
  /**
   * Add trim function to all Strings.
   * @return {String} String trimmed of whitespace.
   */
  String.prototype.trim = function() {
    return this.replace(/^\s+|\s+$/g, '');
  };
}

/**
 * Wrapper function to minimize global namespace pollution.
 * @return {Object} external API to inner functions.
 */
var io = (function() {

  /**
   * Shortcut to get DOM elements by ID.
   * @param {String} node ID of element to find.
   * @return {Object} DOM element.
   */
  var el = function(node) {
    return document.getElementById(node);
  };

  /**
   * Wraps an event listener function to normalize event attributes.
   * Used for IE event handling.
   * @param {Function} func event handler function.
   * @return {Function} Event handler that calls original function
   *   with modified event object.
   */
  var ensureEvent = function(func) {
    return function() {
      var e = window.event;
      e.target = e.srcElement;
      e.preventDefault = function() {
        e.returnValue = false;
      };
      e.stopPropagation = function() {
        e.cancelBubble = true;
      };
      func.call(e.srcElement, e);
    };
  };

  /**
   * Cross-browser support for adding event listeners.
   * Overwrites itself based on if it's IE-style or W3C-style.
   * @param {String} evnt Event name.
   * @param {Object} elem DOM element to attach event to.
   * @param {Function} Func event callback function to apply.
   */
  var listen = function(evnt, elem, func) {
    if (elem.addEventListener) {
      listen = function(evnt, elem, func) {
        elem.addEventListener(evnt, func, false);
      };
    } else if (elem.attachEvent) {
      listen = function(evnt, elem, func) {
        elem['on' + evnt] = ensureEvent(func);
      };
    }
    listen(evnt, elem, func);
  };

  /**
   * Cross-browser support for removing event listeners.
   * Overwrites itself based on if it's IE-style or W3C-style.
   * @param {String} evnt Event name.
   * @param {Object} elem DOM element to attach event to.
   * @param {Function} Func event callback function to apply.
   */
  var unlisten = function(evnt, elem, func) {
    if (elem.removeEventListener) {
      unlisten = function(evnt, elem, func) {
        elem.removeEventListener(evnt, func, false);
      };
    } else if (elem.attachEvent) {
      unlisten = function(evnt, elem, func) {
        elem['on' + evnt] = null;
      };
    }
    unlisten(evnt, elem, func);
  };

  /**
   * Map a function to each item in an array.
   * @param {Array} a Array of items to apply function to.
   * @param {Function} f Function to apply.
   * @return {Array} New array with items returned by function.
   */
  var map = function(a, f) {
    var out = [];
    for (var i = 0, len = a.length; i < len; i++) {
      out[i] = f.call(a, a[i]);
    }
    return out;
  };

  /**
   * Public interface
   * @return {Object} The io object.
   */
  return {
    el: el,
    listen: listen,
    unlisten: unlisten,
    map: map
  };

}());