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


    var queue = [];
    var user;
    var generation = 0;

    on(session, 'change', setUser);
    setUser(session.get());

    function setUser(newUser) {
        user = newUser;
        generation += 1;
        if ( user ) {
            // we make a local copy, just in case the requests cause
            // events to happen
            var q = queue;
            queue = [];
            array.forEach(q,real_request);
        } else {
            session.restore();
        }
    }

    function real_request(item) {
        var req_generation = generation;
        var req = xhr(item.method,lang.mixin(item.options||{},{
            failOk: true
        }));
        item.promise.ioArgs = req.ioArgs;

        console.log("Do request",item.options.url);
        req.then(function(result) {
            item.dfd.resolve(result);
        }, function(error){
            if ( error.response.status === 401 ) {
                if ( user ) {
                    if ( req_generation === generation ) {
                        console.log("Retry after reauthentication",item.options.url);
                        // we need to reauth
                        queue.push(item);
                        setUser(null);
                    } else {
                        console.log("Retry immediately",item.options.url);
                        // we already did, redo request right away
                        real_request(item);
                    }
                } else {
                    console.log("Retry when authenticated",item.options.url);
                    queue.push(item);
                }
            } else {
                item.dfd.reject(error);
            }
        });
    }
    
    var _xhr = 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
        if ( user ) {
            console.log("Immediate",options.url);
            real_request(item);
        } else {
            console.log("Delay until authenticated",options.url);
            queue.push(item);
        }
        return item.promise;
    };

    return _xhr;
});