bryanerayner · October 16, 2015 20:14 · Oct 16, 2015
diff --git a/StreamQueue.js b/StreamQueue.js
@@ -0,0 +1,77 @@
+
+var StreamQueue = (function () {
+
+    function StreamQueue() {
+        // The factory
+        this.nextTaskFactory = null;
+        // The current task
+        this.currentTask = null;
+
+        // Tasks which must have end() called on them.
+        this.tasksToEnd = [];
+    }
+
+    /**
+     * 
+     * @param taskFactory A function which should return the next task.
+     */
+    StreamQueue.prototype.currentTaskEnded = function () {
+
+        gUtil.log('Finished');
+
+        this.currentTask = null;
+        if (this.nextTaskFactory) {
+            var nextTask = this.nextTaskFactory();
+
+            this.nextTaskFactory = null;
+            this.currentTask = nextTask;
+
+            // When we were queuing tasks, we were returning
+            // streams. We must signify 'end' on all those streams, when
+            // the now current task has finished.
+            var tasksToEnd = [].concat(this.tasksToEnd);
+            this.tasksToEnd = [];
+
+            var _this = this;
+            this.currentTask.on('end', function () {
+                // Signify to everything that was listening to the 'next stream' that it's finished now.
+                _.each(tasksToEnd, function (task) {
+                    task.end();
+                });
+                tasksToEnd = [];
+
+                _this.currentTaskEnded();
+            });
+        }
+    };
+
+    /**
+     * 
+     * @param taskFactory A function which should return the next task.
+     */
+    StreamQueue.prototype.queueTask = function (taskFactory) {
+        var _this = this;
+        if (!this.currentTask) {
+            gUtil.log('Starting');
+            this.currentTask = taskFactory();
+            var currentTaskEnded = function () {
+                _this.currentTaskEnded();
+            };
+            this.currentTask
+                .on('end', currentTaskEnded);
+            return this.currentTask;
+        } else {
+            gUtil.log('Task already in progress - queued next task.');
+            if (!this.nextTaskFactory) {
+                this.nextTaskFactory = taskFactory;
+            }
+
+            var ws = Writable();
+            this.tasksToEnd.push(ws);
+
+            return ws;
+        }
+    };
+
+    return StreamQueue;
+})();