/** rft/ui/content - Load page content
 *
 * The rft/ui/content module is responsible for loading content in the app.
 * Content is loaded by calling:
 *    content.goTo('pageId');
 * The page is then loaded from pages/pageId.html. This should contain one top node.
 * This top node gets a _Page widget instantiated on it. The template should not
 * specify another widget on the topnode. A page controller can be specified by
 * the data-rft-mixin attribute to a class inherited from _PageController.
 * You can also specify methods in the template in script tags as:
 *     <script type="rft/method" data-rft-method-name="onVisit|onLeave">
 *        // code
 *     </script>
 * The two relevant events are onVisit and onLeave. After loading and starting
 * the complete page onVisit is called. Use this to link widgets together and
 * load any dynamic content not handled by widget logic already.
 * The event onLeave is called before navigating to another page. If false is 
 * returned from this function, the navigation will be cancelled. You can use 
 * this e.g. to ask confirmation of changed values are not saved.
 */
define(['dojo/_base/declare','dojo/_base/connect','dojo/_base/xhr',
    'dojo/_base/lang','dojo/_base/Deferred','dojo/hash',
    'dojo/io-query','dijit','rft/util','rft/ui/_Page'],
    function(declare,connect,xhr,lang,Deferred,hash,uriQuery,dijit,util,_Page){
        return new (function() {
            var self = this;
            var currentHash = "";
            var currentPage = null;
            
            var HRI = declare(null,{
                constructor: function() {
                    this._path = this._fixPath('/');
                    this._args = {};
                    if ( arguments.length == 1 ) {
                        this.hash(arguments[0]);
                    } else if ( arguments.length == 2 ) {
                        this.path(arguments[0]);
                        this.args(arguments[1]);
                    }
                },
                path: function(path) {
                    if ( path )
                        this._path = this._fixPath(path);
                    return this._path;
                },
                args: function(args) {
                    if ( args && lang.isObject(args) )
                        this._args = args;
                    return this._args;
                },
                hash: function(hash) {
                    if ( hash && lang.isString(hash) ) {
                        var parts = hash.split('!');
                        if ( parts[1] )
                            this._path = this._fixPath(parts[1]);
                        if ( parts[2] )
                            this._args = uriQuery.queryToObject(parts[2]);
                    }
                    return '!'+this._path+'!'+uriQuery.objectToQuery(this._args);
                },
                _fixPath: function(path) {
                    if ( !lang.isString(path) || util.isEmptyString(path) ) {
                        path = "/";
                    }
                    if ( path[0] != '/' ) {
                        path = '/'+path;
                    }
                    if ( path[path.length-1] == '/' ) {
                        path = path + "index";
                    }
                    return path;
                }
            });

            function _goTo(hri,replace) {
                var contentPane = dijit.byId('content');
                var dfd = new Deferred();
                var newHash = hri.hash();
                
                // if already there, return
                if ( currentHash === newHash ) {
                    dfd.resolve();
                    return dfd.promise;
                }
                
                // check if we can leave current page
                if ( currentPage ) {
                    if ( currentPage.onLeave() === false ) {
                        // restore hash if changed by hand or back button
                        hash(currentHash);
                        dfd.reject();
                        return dfd.promise;
                    }
                    currentPage = null;
                }
                
                // update hash
                currentHash = newHash;
                hash(newHash,replace);
                
                // load html
                var pageUrl = 'rft/pages'+hri.path()+'.html';
                xhr.get({
                    url: pageUrl,
                    failOk: true
                })
                
                // initialize page or create error message
                .then(function(html){
                    contentPane.set('content',html);
                    var rootNode = contentPane.containerNode.firstChild;
                    currentPage = dijit.byNode(rootNode);
                    if ( !currentPage ) {
                        currentPage = new _Page({},rootNode);
                    }
                    dfd.resolve();
                },function(){
                    contentPane.set('content',"<div>Page "+hri.path()+" not found.</div>");
                    dfd.reject();
                });
                return dfd.promise;
            }

            self.initial = function(path,args) {
                if ( currentHash ) {
                    var dfd = new Deferred();
                    dfd.resolve();
                    return dfd.promise;
                }
                if ( hash() ) {
                    var hri = new HRI(hash());
                    return _goTo(hri, true);
                } else {
                    return _goTo(new HRI(path,args));
                }
            }

            self.goTo = function(path,args) {
                return _goTo(new HRI(path,args));
            }

            connect.subscribe('/dojo/hashchange', function(){
                _goTo(new HRI(hash()));
            });

        })();
    });