goog.provide('webfont.DomHelper');

/**

* Handles common DOM manipulation tasks. The aim of this library is to cover
* the needs of typical font loading. Not more, not less.
* @param {Window} mainWindow The main window webfontloader.js is loaded in.
* @param {Window=} opt_loadWindow The window we'll load the font into. By
*   default, the main window is used.
* @constructor
*/

webfont.DomHelper = function(mainWindow, opt_loadWindow) {

this.mainWindow_ = mainWindow;
this.loadWindow_ = opt_loadWindow || mainWindow;

/** @type {string} */
this.protocol_;

/** @type {Document} */
this.document_ = this.loadWindow_.document;

};

goog.scope(function () {

var DomHelper = webfont.DomHelper;

/**
 * The NativeFontWatchRunnner depends on the correct and reliable
 * |onload| event, and browsers with the native font loading API
 * have reliable @onload support as far as we know. So we use the
 * event for such a case and unconditionally invokes the callback
 * otherwise.
 *
 * @const
 * @type {boolean}
 */
DomHelper.CAN_WAIT_STYLESHEET = !!window['FontFace'];

/**
 * Creates an element.
 * @param {string} elem The element type.
 * @param {Object=} opt_attr A hash of attribute key/value pairs.
 * @param {string=} opt_innerHtml Contents of the element.
 * @return {Element} the new element.
 */
DomHelper.prototype.createElement = function(elem, opt_attr,
    opt_innerHtml) {
  var domElement = this.document_.createElement(elem);

  if (opt_attr) {
    for (var attr in opt_attr) {
      // protect against native prototype augmentations
      if (opt_attr.hasOwnProperty(attr)) {
        if (attr == "style") {
          this.setStyle(domElement, opt_attr[attr]);
        } else {
          domElement.setAttribute(attr, opt_attr[attr]);
        }
      }
    }
  }
  if (opt_innerHtml) {
    domElement.appendChild(this.document_.createTextNode(opt_innerHtml));
  }
  return domElement;
};

/**
 * Inserts an element into the document. This is intended for unambiguous
 * elements such as html, body, head.
 * @param {string} tagName The element name.
 * @param {Element} e The element to append.
 * @return {boolean} True if the element was inserted.
 */
DomHelper.prototype.insertInto = function(tagName, e) {
  var t = this.document_.getElementsByTagName(tagName)[0];

  if (!t) { // opera allows documents without a head
    t = document.documentElement;
  }

  // This is safer than appendChild in IE. appendChild causes random
  // JS errors in IE. Sometimes errors in other JS exectution, sometimes
  // complete 'This page cannot be displayed' errors. For our purposes,
  // it's equivalent because we don't need to insert at any specific
  // location.
  t.insertBefore(e, t.lastChild);
  return true;
};

/**
 * Calls a function when the body tag exists.
 * @param {function()} callback The function to call.
 */
DomHelper.prototype.whenBodyExists = function(callback) {
  var that = this;

  if (that.document_.body) {
    callback();
  } else {
    if (that.document_.addEventListener) {
      that.document_.addEventListener('DOMContentLoaded', callback);
    } else {
      that.document_.attachEvent('onreadystatechange', function () {
        if (that.document_.readyState == 'interactive' || that.document_.readyState == 'complete') {
          callback();
        }
      });
    }
  }
};

/**
 * Removes an element from the DOM.
 * @param {Element} node The element to remove.
 * @return {boolean} True if the element was removed.
 */
DomHelper.prototype.removeElement = function(node) {
  if (node.parentNode) {
    node.parentNode.removeChild(node);
    return true;
  }
  return false;
};

/**
 * @deprecated Use updateClassName().
 *
 * Appends a name to an element's class attribute.
 * @param {Element} e The element.
 * @param {string} name The class name to add.
 */
DomHelper.prototype.appendClassName = function(e, name) {
  this.updateClassName(e, [name]);
};

/**
 * @deprecated Use updateClassName().
 *
 * Removes a name to an element's class attribute.
 * @param {Element} e The element.
 * @param {string} name The class name to remove.
 */
DomHelper.prototype.removeClassName = function(e, name) {
  this.updateClassName(e, null, [name]);
};

/**
 * Updates an element's class attribute in a single change. This
 * allows multiple updates in a single class name change so there
 * is no chance for a browser to relayout in between changes.
 *
 * @param {Element} e The element.
 * @param {Array.<string>=} opt_add List of class names to add.
 * @param {Array.<string>=} opt_remove List of class names to remove.
 */
DomHelper.prototype.updateClassName = function (e, opt_add, opt_remove) {
  var add = opt_add || [],
      remove = opt_remove || [];

  var classes = e.className.split(/\s+/);

  for (var i = 0; i < add.length; i += 1) {
    var found = false;

    for (var j = 0; j < classes.length; j += 1) {
      if (add[i] === classes[j]) {
        found = true;
        break;
      }
    }

    if (!found) {
      classes.push(add[i]);
    }
  }

  var remainingClasses = [];

  for (var i = 0; i < classes.length; i += 1) {
    var found = false;

    for (var j = 0; j < remove.length; j += 1) {
      if (classes[i] === remove[j]) {
        found = true;
        break;
      }
    }

    if (!found) {
      remainingClasses.push(classes[i]);
    }
  }

  e.className = remainingClasses.join(' ')
                  .replace(/\s+/g, ' ')
                  .replace(/^\s+|\s+$/, '');
};

/**
 * Returns true if an element has a given class name and false otherwise.
 * @param {Element} e The element.
 * @param {string} name The class name to check for.
 * @return {boolean} Whether or not the element has this class name.
 */
DomHelper.prototype.hasClassName = function(e, name) {
  var classes = e.className.split(/\s+/);
  for (var i = 0, len = classes.length; i < len; i++) {
    if (classes[i] == name) {
      return true;
    }
  }
  return false;
};

/**
 * Sets the style attribute on an element.
 * @param {Element} e The element.
 * @param {string} styleString The style string.
 */
DomHelper.prototype.setStyle = function(e, styleString) {
  e.style.cssText = styleString;
};

/**
 * @return {Window} The main window webfontloader.js is loaded in (for config).
 */
DomHelper.prototype.getMainWindow = function() {
  return this.mainWindow_;
};

/**
 * @return {Window} The window that we're loading the font(s) into.
 */
DomHelper.prototype.getLoadWindow = function() {
  return this.loadWindow_;
};

/**
 * Returns the hostname of the current document.
 * @return {string} hostname.
 */
DomHelper.prototype.getHostName = function() {
  return this.getLoadWindow().location.hostname || this.getMainWindow().location.hostname;
};

/**
 * Creates a style element.
 * @param {string} css Contents of the style element.
 * @return {Element} a DOM element.
 */
DomHelper.prototype.createStyle = function(css) {
  var e = this.createElement('style');

  e.setAttribute('type', 'text/css');
  if (e.styleSheet) { // IE
    e.styleSheet.cssText = css;
  } else {
    e.appendChild(document.createTextNode(css));
  }
  return e;
};

/**
 * Loads an external stylesheet.
 *
 * @param {string} href the URL of the stylesheet
 * @param {function(Error)=} opt_callback Called when the stylesheet has loaded or failed to
 * load. Note that the callback is *NOT* guaranteed to be called in all browsers. The first
 * argument to the callback is an error object that is falsy when there are no errors and
 * truthy when there are.
 * @param {boolean=} opt_async True if the stylesheet should be loaded asynchronously. Defaults to false.
 * @return {Element} The link element
 */
DomHelper.prototype.loadStylesheet = function (href, opt_callback, opt_async) {
  var link = this.createElement('link', {
    'rel': 'stylesheet',
    'href': href,
    'media': (opt_async ? 'only x' : 'all')
  });

  var sheets = this.document_.styleSheets,
      eventFired = false,
      asyncResolved = !opt_async,
      callbackArg = null,
      callback = opt_callback || null;

  function mayInvokeCallback() {
    if (callback && eventFired && asyncResolved) {
      callback(callbackArg);
      callback = null;
    }
  }

  if (DomHelper.CAN_WAIT_STYLESHEET) {
    link.onload = function () {
      eventFired = true;
      mayInvokeCallback();
    };

    link.onerror = function () {
      eventFired = true;
      callbackArg = new Error('Stylesheet failed to load');
      mayInvokeCallback();
    };
  } else {
    // Some callers expect opt_callback being called asynchronously.
    setTimeout(function () {
      eventFired = true;
      mayInvokeCallback();
    }, 0);
  }

  function onStylesheetAvailable(callback) {
    for (var i = 0; i < sheets.length; i++) {
      if (sheets[i].href && sheets[i].href.indexOf(href) !== -1) {
        return callback();
      }
    }

    setTimeout(function () {
      onStylesheetAvailable(callback);
    }, 0);
  }

  function onMediaAvailable(callback) {
    for (var i = 0; i < sheets.length; i++) {
      if (sheets[i].href && sheets[i].href.indexOf(href) !== -1 && sheets[i].media) {
        /**
         * @type {string|MediaList|null}
         */
        var media = sheets[i].media;

        if (media === "all" || (media.mediaText && media.mediaText === "all")) {
          return callback();
        }
      }
    }

    setTimeout(function () {
      onMediaAvailable(callback);
    }, 0);
  }

  this.insertInto('head', link);

  if (opt_async) {
    onStylesheetAvailable(function () {
      link.media = "all";
      // The media type change doesn't take effect immediately on Chrome, so
      // we'll query the media attribute on the stylesheet until it changes
      // to "all".
      onMediaAvailable(function () {
        asyncResolved = true;
        mayInvokeCallback();
      });
    });
  }

  return link;
};

/**
 * Loads an external script file.
 * @param {string} src URL of the script.
 * @param {function(Error)=} opt_callback callback when the script has loaded. The first argument to
 * the callback is an error object that is falsy when there are no errors and truthy when there are.
 * @param {number=} opt_timeout The number of milliseconds after which the callback will be called
 * with a timeout error. Defaults to 5 seconds.
 * @return {Element} The script element
 */
DomHelper.prototype.loadScript = function(src, opt_callback, opt_timeout) {
  var head = this.document_.getElementsByTagName('head')[0];

  if (head) {
    var script = this.createElement('script', {
      'src': src
    });
    var done = false;
    script.onload = script.onreadystatechange = function() {
      if (!done && (!this.readyState || this.readyState == 'loaded' || this.readyState == 'complete')) {
        done = true;
        if (opt_callback) {
          opt_callback(null);
        }
        script.onload = script.onreadystatechange = null;
        // Avoid a bizarre issue with unclosed <base> tag in IE6 - http://blog.dotsmart.net/2008/04/
        if (script.parentNode.tagName == 'HEAD') head.removeChild(script);
      }
    };
    head.appendChild(script);

    setTimeout(function () {
      if (!done) {
        done = true;
        if (opt_callback) {
          opt_callback(new Error('Script load timeout'));
        }
      }
    }, opt_timeout || 5000);

    return script;
  }

  return null;
};

});