GroupedGet

GroupedGet

var GroupedGet = function(getterFn, massGetterFn) {
    var thisGroupService = this;
    thisGroupService._items = {};
    thisGroupService._pendingItems = {};

    thisGroupService._singleGet = getterFn;
    thisGroupService._massGet = massGetterFn;

    thisGroupService.sendMassGet = thisGroupService.sendMassGet.bind(this);
    thisGroupService.get = thisGroupService.get.bind(this);
};

GroupedGet.prototype._wait = 50;
GroupedGet.prototype._max = 10;

GroupedGet.prototype.createPromise = function() {
    var defer = {};
    defer.promise = new Promise(function(resolve, reject) {
        defer.resolve = resolve;
        defer.reject = reject;
    });

    return defer;
};

GroupedGet.prototype.sendMassGet = function() {
    var thisGroupService = this;

    var ids = Object.keys(thisGroupService._pendingItems);
    if (ids.length) {
        thisGroupService._pendingItems = {};
        thisGroupService._massGet(ids).then(
            function() {
                ids.forEach(function(id) {
                    thisGroupService._items[id].resolve();
                });
            },
            function() {
                ids.forEach(function(id) {
                    thisGroupService._items[id].reject();
                });
            }
        );
    }
};

GroupedGet.prototype.get = function(id) {
    var thisGroupService = this;

    var promiseForId = thisGroupService._items[id];
    if (promiseForId) {
        return promiseForId.promise;
    }

    var promiseForId = thisGroupService.createPromise();
    thisGroupService._items[id] = promiseForId;
    thisGroupService._pendingItems[id] = promiseForId;
    promiseForId.promise = promiseForId.promise.then(
        function() {
            delete thisGroupService._items[id];
            var item = thisGroupService._singleGet(id);
            return item;
        },
        function() {
            delete thisGroupService._items[id];
        }
    );

    window.clearTimeout(thisGroupService._debounceId);
    var ids = Object.keys(thisGroupService._pendingItems);
    if (ids.length >= thisGroupService._max) {
        thisGroupService.sendMassGet();
    } else {
        thisGroupService._debounceId = window.setTimeout(function() {
            thisGroupService.sendMassGet();
        }, thisGroupService._wait);
    }

    return promiseForId.promise;
};