refactor: isolate Location controls and cancellable search

src/ui/locationSearch.js

@@ -0,0 +1,49 @@
+/** One cancellable place lookup at a time, under the caller's camera authority. */
+export class LocationSearch {
+  constructor({ input, begin, isCurrent, beforeFly, search, onStart, onResult, onMissing, onError, onSettled }) {
+    Object.assign(this, { input, begin, isCurrent, beforeFly, search, onStart, onResult, onMissing, onError, onSettled });
+    this.controller = null;
+    this.generation = 0;
+    this.destroyed = false;
+  }
+  async run(query) {
+    query = String(query || '').trim();
+    if (!query || this.destroyed) return;
+    const authority = this.begin();
+    if (authority === false) {
+      this.input.classList.remove('searching');
+      this.input.blur();
+      return;
+    }
+    this.controller?.abort();
+    const controller = new AbortController();
+    this.controller = controller;
+    const generation = ++this.generation;
+    const current = () => !this.destroyed && generation === this.generation && this.isCurrent(authority);
+    this.onStart(authority);
+    this.input.classList.add('searching');
+    try {
+      const destination = await this.search(query, {
+        signal: controller.signal,
+        beforeFly: () => current() && this.beforeFly(authority),
+      });
+      if (!current() || controller.signal.aborted) return;
+      if (destination?.cancelled) return;
+      if (destination) this.onResult(destination, query);
+      else this.onMissing();
+    } catch (error) {
+      if (controller.signal.aborted || !current()) return;
+      this.onError(error);
+    } finally {
+      if (this.controller === controller) this.controller = null;
+      if (!this.destroyed) this.onSettled(authority);
+    }
+  }
+  destroy() {
+    if (this.destroyed) return;
+    this.destroyed = true;
+    this.generation++;
+    this.controller?.abort();
+    this.controller = null;
+  }
+}