location image search and population for new session

lib/services/functional/debouncer.dart

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+import 'dart:async';
+
+typedef _Debounceable<S, T> = Future<S?> Function(T parameter);
+
+class Debouncer {
+  Debouncer(this._duration, this._callback);
+
+  final Duration _duration;
+  final dynamic _callback;
+  late final _Debounceable<dynamic, String> _debouncedSearch = _debounce<dynamic, String>(_callback);
+
+  /// Returns a new function that is a debounced version of the given function.
+  ///
+  /// This means that the original function will be called only after no calls
+  /// have been made for the given Duration.
+  _Debounceable<S, T> _debounce<S, T>(_Debounceable<S?, T> function) {
+    _DebounceTimer? debounceTimer;
+
+    return (T parameter) async {
+      if (debounceTimer != null && !debounceTimer!.isCompleted) {
+        debounceTimer!.cancel();
+      }
+      debounceTimer = _DebounceTimer(_duration);
+      try {
+        await debounceTimer!.future;
+      } on _CancelException {
+        return null;
+      }
+      return function(parameter);
+    };
+  }
+
+  process(data) {
+    return _debouncedSearch(data);
+  }
+}
+
+// A wrapper around Timer used for debouncing.
+class _DebounceTimer {
+  final Duration debounceDuration;
+
+  _DebounceTimer(
+    this.debounceDuration
+  ) {
+    _timer = Timer(debounceDuration, _onComplete);
+  }
+
+  late final Timer _timer;
+  final Completer<void> _completer = Completer<void>();
+
+  void _onComplete() {
+    _completer.complete();
+  }
+
+  Future<void> get future => _completer.future;
+
+  bool get isCompleted => _completer.isCompleted;
+
+  void cancel() {
+    _timer.cancel();
+    _completer.completeError(const _CancelException());
+  }
+}
+
+// An exception indicating that the timer was canceled.
+class _CancelException implements Exception {
+  const _CancelException();
+}