Various refactoring

src/app/core/tab-persist.strategy.ts

@@ -0,0 +1,27 @@
+import { RouteReuseStrategy, ActivatedRouteSnapshot, DetachedRouteHandle } from '@angular/router'
+
+/**
+ * This makes each route with the 'reuse' data flag persist when not in focus.
+ */
+export class TabPersistStrategy extends RouteReuseStrategy {
+  private handles: { [path: string]: DetachedRouteHandle } = {}
+
+  shouldDetach(route: ActivatedRouteSnapshot) {
+    return route.data.shouldReuse || false
+  }
+  store(route: ActivatedRouteSnapshot, handle: DetachedRouteHandle) {
+    if (route.data.shouldReuse) {
+      this.handles[route.routeConfig.path] = handle
+    }
+  }
+  shouldAttach(route: ActivatedRouteSnapshot) {
+    return !!route.routeConfig && !!this.handles[route.routeConfig.path]
+  }
+  retrieve(route: ActivatedRouteSnapshot) {
+    if (!route.routeConfig) return null
+    return this.handles[route.routeConfig.path]
+  }
+  shouldReuseRoute(future: ActivatedRouteSnapshot, _curr: ActivatedRouteSnapshot) {
+    return future.data.shouldReuse || false
+  }
+}