More refactoring: using a decent, configurable datapipeline now

Logic/FeatureSource/FeatureSourceMerger.ts

@@ -0,0 +1,40 @@
+import FeatureSource from "./FeatureSource";
+import {UIEventSource} from "../UIEventSource";
+
+export default class FeatureSourceMerger implements FeatureSource {
+
+    public features: UIEventSource<{ feature: any; freshness: Date }[]> = new UIEventSource<{feature: any; freshness: Date}[]>([]);
+    private readonly _sources: FeatureSource[];
+
+    constructor(sources: FeatureSource[]) {
+        this._sources = sources;
+        const self = this;
+        for (const source of sources) {
+            source.features.addCallback(() => self.Update());
+        }
+    }
+
+    private Update() {
+        let all = {}; // Mapping 'id' -> {feature, freshness}
+        for (const source of this._sources) {
+            for (const f of source.features.data) {
+                const id = f.feature.properties.id+f.feature.geometry.type;
+                const oldV = all[id];
+                if(oldV === undefined){
+                    all[id] = f;
+                }else{
+                    if(oldV.freshness < f.freshness){
+                        all[id]=f;
+                    }
+                }
+            }
+        }
+        const newList = [];
+        for (const id in all) {
+            newList.push(all[id]);
+        }
+        this.features.setData(newList);
+    }
+
+
+}