add debounce hook

lib/hooks/debounce.dart

@@ -0,0 +1,58 @@
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+import 'package:flutter_hooks/flutter_hooks.dart';
+
+import 'ref.dart';
+
+class Debounce {
+  final bool pending;
+  final bool loading;
+  final void Function() start;
+  final void Function() cancel;
+  final void Function() reset;
+
+  const Debounce({
+    @required this.pending,
+    @required this.loading,
+    @required this.start,
+    @required this.cancel,
+    @required this.reset,
+  });
+}
+
+/// When loading is [.start()]ed, it goes into a pending state
+/// and loading is triggered after [delayDuration].
+/// Everything can be reset with [.cancel()]
+Debounce useDebounce(
+  Function(Function cancel) onDebounce, [
+  Duration delayDuration = const Duration(milliseconds: 500),
+]) {
+  final loading = useState(false);
+  final pending = useState(false);
+  final timerHandle = useRef<Timer>(null);
+
+  cancel() {
+    timerHandle.current?.cancel();
+    pending.value = false;
+    loading.value = false;
+  }
+
+  start() {
+    timerHandle.current = Timer(delayDuration, () {
+      loading.value = true;
+      onDebounce(cancel);
+    });
+    pending.value = true;
+  }
+
+  return Debounce(
+      loading: loading.value,
+      pending: pending.value,
+      start: start,
+      cancel: cancel,
+      reset: () {
+        cancel();
+        start();
+      });
+}