Huge refactoring of the feature pipeline, WIP

Logic/FeatureSource/Sources/RememberingSource.ts

@@ -0,0 +1,32 @@
+
+import FeatureSource, {FeatureSourceForLayer} from "./FeatureSource";
+import {UIEventSource} from "../UIEventSource";
+import FilteredLayer from "../../Models/FilteredLayer";
+/**
+ * Every previously added point is remembered, but new points are added.
+ * Data coming from upstream will always overwrite a previous value
+ */
+export default class RememberingSource implements FeatureSource {
+
+    public readonly features: UIEventSource<{ feature: any, freshness: Date }[]>;
+    public readonly name;
+
+    constructor(source: FeatureSource) {
+        const self = this;
+        this.name = "RememberingSource of " + source.name;
+        const empty = [];
+        this.features = source.features.map(features => {
+            const oldFeatures = self.features?.data ?? empty;
+            if (features === undefined) {
+                return oldFeatures;
+            }
+
+            // Then new ids
+            const ids = new Set<string>(features.map(f => f.feature.properties.id + f.feature.geometry.type));
+            // the old data
+            const oldData = oldFeatures.filter(old => !ids.has(old.feature.properties.id + old.feature.geometry.type))
+            return [...features, ...oldData];
+        })
+    }
+
+}