/*
 * Copyright 2008 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

function __MODULE_FUNC__() {
  // ---------------- INTERNAL GLOBALS ----------------
  
  // Cache symbols locally for good obfuscation
  var $wnd = window
  ,$doc = document
  
  // These variables gate calling gwtOnLoad; all must be true to start
  ,gwtOnLoad, bodyDone

  // If non-empty, an alternate base url for this module
  ,base = ''
  
  // A map of properties that were declared in meta tags
  ,metaProps = {}
  
  // Maps property names onto sets of legal values for that property.
  ,values = []
  
  // Maps property names onto a function to compute that property.
  ,providers = []
  
  // A multi-tier lookup map that uses actual property values to quickly find
  // the strong name of the cache.js file to load.
  ,answers = []

  // Error functions.  Default unset in compiled mode, may be set by meta props.
  ,onLoadErrorFunc, propertyErrorFunc
  
  ; // end of global vars

  // ------------------ TRUE GLOBALS ------------------

  // Maps to synchronize the loading of styles and scripts; resources are loaded
  // only once, even when multiple modules depend on them.  This API must not
  // change across GWT versions.
  if (!$wnd.__gwt_stylesLoaded) { $wnd.__gwt_stylesLoaded = {}; }
  if (!$wnd.__gwt_scriptsLoaded) { $wnd.__gwt_scriptsLoaded = {}; }

  // --------------- INTERNAL FUNCTIONS ---------------

  function isHostedMode() {
    var result = false;
    try {
      var query = $wnd.location.search;
      return (query.indexOf('gwt.codesvr=') != -1
          || query.indexOf('gwt.hosted=') != -1 
          || ($wnd.external && $wnd.external.gwtOnLoad)) &&
          (query.indexOf('gwt.hybrid') == -1);
    } catch (e) {
      // Defensive: some versions of IE7 reportedly can throw an exception
      // evaluating "external.gwtOnLoad".
    }
    isHostedMode = function() { return result; };
    return result;
  }
  
  // Called by onScriptLoad() and onload(). It causes
  // the specified module to be cranked up.
  //
  function maybeStartModule() {
    // TODO: it may not be necessary to check gwtOnLoad here.
    if (gwtOnLoad && bodyDone) {
      gwtOnLoad(onLoadErrorFunc, '__MODULE_NAME__', base);
    }
  }

  // Determine our own script's URL via magic :)
  // This function produces one side-effect, it sets base to the module's
  // base url.
  //
  function computeScriptBase() {
    var thisScript
    ,markerId = "__gwt_marker___MODULE_NAME__"
    ,markerScript;

    $doc.write('<script id="' + markerId + '"></script>');
    markerScript = $doc.getElementById(markerId);

    // Our script element is assumed to be the closest previous script element
    // to the marker, so start at the marker and walk backwards until we find
    // a script.
    thisScript = markerScript && markerScript.previousSibling;
    while (thisScript && thisScript.tagName != 'SCRIPT') {
      thisScript = thisScript.previousSibling;
    }

    // Gets the part of a url up to and including the 'path' portion.
    function getDirectoryOfFile(path) {
      // Truncate starting at the first '?' or '#', whichever comes first. 
      var hashIndex = path.lastIndexOf('#');
      if (hashIndex == -1) {
        hashIndex = path.length;
      }
      var queryIndex = path.indexOf('?');
      if (queryIndex == -1) {
        queryIndex = path.length;
      }
      var slashIndex = path.lastIndexOf('/', Math.min(queryIndex, hashIndex));
      return (slashIndex >= 0) ? path.substring(0, slashIndex + 1) : '';
    };

    if (thisScript && thisScript.src) {
      // Compute our base url
      base = getDirectoryOfFile(thisScript.src);
    }

    // Make the base URL absolute
    if (base == '') {
      // If there's a base tag, use it.
      var baseElements = $doc.getElementsByTagName('base');
      if (baseElements.length > 0) {
        // It's always the last parsed base tag that will apply to this script.
        base = baseElements[baseElements.length - 1].href;
      } else {
        // No base tag; the base must be the same as the document location.
        base = getDirectoryOfFile($doc.location.href);
      }
    } else if ((base.match(/^\w+:\/\//))) {
      // If the URL is obviously absolute, do nothing.
    } else {
      // Probably a relative URL; use magic to make the browser absolutify it.
      // I wish there were a better way to do this, but this seems the only
      // sure way!  (A side benefit is it preloads clear.cache.gif)
      // Note: this trick is harmless if the URL was really already absolute.
      var img = $doc.createElement("img");
      img.src = base + 'clear.cache.gif';
      base = getDirectoryOfFile(img.src);
    }

    if (markerScript) {
      // remove the marker element
      markerScript.parentNode.removeChild(markerScript);
    }
  }
  
  // Called to slurp up all <meta> tags:
  // gwt:property, gwt:onPropertyErrorFn, gwt:onLoadErrorFn
  //
  function processMetas() {
    var metas = document.getElementsByTagName('meta');
    for (var i = 0, n = metas.length; i < n; ++i) {
      var meta = metas[i], name = meta.getAttribute('name'), content;
  
      if (name) {
        if (name == 'gwt:property') {
          content = meta.getAttribute('content');
          if (content) {
            var value, eq = content.indexOf('=');
            if (eq >= 0) {
              name = content.substring(0, eq);
              value = content.substring(eq+1);
            } else {
              name = content;
              value = '';
            }
            metaProps[name] = value;
          }
        } else if (name == 'gwt:onPropertyErrorFn') {
          content = meta.getAttribute('content');
          if (content) {
            try {
              propertyErrorFunc = eval(content);
            } catch (e) {
              alert('Bad handler \"' + content +
                '\" for \"gwt:onPropertyErrorFn\"');
            }
          }
        } else if (name == 'gwt:onLoadErrorFn') {
          content = meta.getAttribute('content');
          if (content) {
            try {
              onLoadErrorFunc = eval(content);
            } catch (e) {
              alert('Bad handler \"' + content + '\" for \"gwt:onLoadErrorFn\"');
            }
          }
        }
      }
    }
  }

  /**
   * Determines whether or not a particular property value is allowed. Called by
   * property providers.
   * 
   * @param propName the name of the property being checked
   * @param propValue the property value being tested
   */
  function __gwt_isKnownPropertyValue(propName, propValue) {
    return propValue in values[propName];
  }

  /**
   * Returns a meta property value, if any.  Used by DefaultPropertyProvider.
   */
  function __gwt_getMetaProperty(name) {
    var value = metaProps[name];
    return (value == null) ? null : value;
  }
  
  // --------------- EXPOSED FUNCTIONS ----------------

  // Called when the compiled script identified by moduleName is done loading.
  //
  __MODULE_FUNC__.onScriptLoad = function(gwtOnLoadFunc) {
    // remove this whole function from the global namespace to allow GC
    __MODULE_FUNC__ = null;
    gwtOnLoad = gwtOnLoadFunc;
    maybeStartModule();
  }

  // --------------- STRAIGHT-LINE CODE ---------------

  if (isHostedMode()) {
    alert("Single-script hosted mode not yet implemented. See issue " +
      "http://code.google.com/p/google-web-toolkit/issues/detail?id=2079");
    return;
  }

  // do it early for compile/browse rebasing
  computeScriptBase();
  processMetas();
  
  // --------------- WINDOW ONLOAD HOOK ---------------

  var onBodyDoneTimerId;
  function onBodyDone() {
    if (!bodyDone) {
      bodyDone = true;
// __MODULE_STYLES_BEGIN__
     // Style resources are injected here to prevent operation aborted errors on ie
// __MODULE_STYLES_END__
      maybeStartModule();

      if ($doc.removeEventListener) {
        $doc.removeEventListener("DOMContentLoaded", onBodyDone, false);
      }
      if (onBodyDoneTimerId) {
        clearInterval(onBodyDoneTimerId);
      }
    }
  }

  // For everyone that supports DOMContentLoaded.
  if ($doc.addEventListener) {
    $doc.addEventListener("DOMContentLoaded", function() {
      onBodyDone();
    }, false);
  }

  // Fallback. If onBodyDone() gets fired twice, it's not a big deal.
  var onBodyDoneTimerId = setInterval(function() {
    if (/loaded|complete/.test($doc.readyState)) {
      onBodyDone();
    }
  }, 50);

// __MODULE_SCRIPTS_BEGIN__
  // Script resources are injected here
// __MODULE_SCRIPTS_END__
}

__MODULE_FUNC__();