Add MapComplete

UI/UIEventSource.ts

@@ -0,0 +1,44 @@
+export class UIEventSource<T>{
+    
+    public data : T;
+    private _callbacks = [];
+
+    constructor(data: T) {
+        this.data = data;
+    }
+
+
+    public addCallback(callback: (() => void)) {
+        this._callbacks.push(callback);
+        return this;
+    }
+
+    public setData(t: T): void {
+        if (this.data === t) {
+            return;
+        }
+        this.data = t;
+        this.ping();
+    }
+
+    public ping(): void {
+        for (let i in this._callbacks) {
+            this._callbacks[i]();
+        }
+    }
+
+    public map<J>(f: ((T) => J)): UIEventSource<J> {
+        const newSource = new UIEventSource<J>(
+            f(this.data)
+        );
+        const self = this;
+        this.addCallback(function () {
+            newSource.setData(f(self.data));
+        });
+
+        return newSource;
+
+    }
+
+
+}