define([
    "./session",
    "dojo/Deferred",
    "dojo/_base/lang",
    "dojo/on",
    "dojo/_base/xhr"
], function(session, Deferred, lang, on, xhr) {

    var user = session.get();
    var queue = [];
    
    on(session, 'change', function(newUser){
        user = newUser;
        retry();
    });

    function retry() {
        if (user && queue.length > 0) {
            var item = queue.shift();
            console.log("Retry",item.options.url);
            real_request(item);
        }
    }
    
    function real_request(item) {
        var req = xhr(item.method,lang.mixin(item.options||{},{
            failOk: true
        }));
        item.promise.ioArgs = req.ioArgs;

        req.then(function(result){
            item.dfd.resolve(result);
            retry();
        }, function(error){
            if ( error.response.status === 401 ) {
                queue.unshift(item);
                session.restore();
            } else {
                item.dfd.reject(error);
                retry();
            }
        });
    }
    
    var _request = function(method, options) {
        var item = {
            method: method,
            options: options,
            dfd: new Deferred()
        };
        item.promise = lang.delegate(item.dfd.promise);
        // only do the request directly if we are authenticated and
        // there are no earlier requests queued.
        if ( user && queue.length === 0 ) {
            console.log("Request",options.url);
            real_request(item);
        } else {
            console.log("Push",options.url);
            queue.push(item);
        }
        return item.promise;
    };

    return _request;
});