define([
    'dojo/_base/declare',
    'dojo/hash',
    'dojo/topic',
    './Content',
    './Page',
    './Path'
],function(declare,hash,topic,Content,Page,Path){

    var Router = declare(null,{
        _started: false,
        _routes: null,
        _previousHash: null,

        constructor: function() {
            this._routes = [];
        },
        startup: function() {
            if ( this._started ) { return; }
            if ( !Content._started ) {
                Content.startup();
            }
            this._started = true;

            var self = this;

            if ( hash() === "" ) {
                hash(Path.getDefault());
            }
            this._handlePathChange(hash());
			topic.subscribe("/dojo/hashchange", function(){
                self._handlePathChange.apply(self,arguments);
            });
        },
        register: function(route) {
            if ( this._started ) {
                console.warn('Registering routes after startup() is called is discouraged.');
            }
            var callback = this._normalizeCallback(route);
            if ( callback ) {
                if ( route.path ) {
                    route.callback = callback;
                    route.path = new Path(route.path);
                    this._routes.push(route);
                } else {
                    this._defaultCallback = callback;
                }
            } else {
                console.warn("Route "+(route.path||"default")+" has no action.");
            }
        },
        _normalizeCallback: function(route) {
            var self = this;
            var callback = null;
            if ( route.callback ) {
                callback = function(params){
                    Content.set(route.callback(params));
                };
            } else if ( route.redirect ) {
                callback = function(params){
                    self.go(route.redirect);
                };
            } else if ( route.constructor ) {
                callback = function(params){
                    Content.set( new route.constructor(params) );
                };
            }
            return callback;
        },
        _handlePathChange: function(newHash) {
            if ( this._previousHash === newHash ) { return; }
            this._previousHash = newHash;
            for (var i = this._routes.length-1; i >= 0; i--) {
                var route = this._routes[i];
                var params = null;
                if ((params = route.path.match(newHash)) !== null) {
                    try {
                        route.callback(params);
                    } catch(err) {
                        console.error("Page change failed.",err);
                    }
                    return;
                }
            }
            try {
                this._defaultCallback();
            } catch(err) {
                console.error("Default page failed.",err);
            }
        },
        go: function(path,args) {
            if ( !this._started ) { return; }
            var newHash = Path.format(path,args);
            this._handlePathChange(newHash);
            hash(newHash);
        },
        _defaultCallback: function() {
            Content.set(new Page({
                templateString: "<div>Requested page not found. Go <a href=\"#"+Path.getDefault()+"\">home</a>.</div>"
            }));
        }
    });

    return new Router();
});