busy handling

packages/async_tools/lib/async_tools.dart

@@ -6,3 +6,4 @@ export 'src/async_value.dart';
 export 'src/serial_future.dart';
 export 'src/single_future.dart';
 export 'src/single_state_processor.dart';
+export 'src/single_stateless_processor.dart';

packages/async_tools/lib/src/single_state_processor.dart

@@ -14,8 +14,7 @@ import '../async_tools.dart';
 class SingleStateProcessor<State> {
   SingleStateProcessor();
 
-  void updateState(State newInputState,
-      {required Future<void> Function(State) closure}) {
+  void updateState(State newInputState, Future<void> Function(State) closure) {
     // Use a singlefuture here to ensure we get dont lose any updates
     // If the input stream gives us an update while we are
     // still processing the last update, the most recent input state will

packages/async_tools/lib/src/single_stateless_processor.dart

@@ -0,0 +1,47 @@
+import 'dart:async';
+
+import '../async_tools.dart';
+
+// Process a single stateless update at a time ensuring each request
+// gets processed asynchronously, and continuously while update is requested.
+//
+// This is useful for processing updates asynchronously without waiting
+// from a synchronous execution context
+class SingleStatelessProcessor {
+  SingleStatelessProcessor();
+
+  void update(Future<void> Function() closure) {
+    singleFuture(this, () async {
+      do {
+        _more = false;
+        await closure();
+
+        // See if another update was requested
+      } while (_more);
+    }, onBusy: () {
+      // Keep this state until we process again
+      _more = true;
+    });
+  }
+
+  // Like update, but with a busy wrapper that clears once the updating is finished
+  void busyUpdate<T, S>(
+      Future<void> Function(Future<void> Function(void Function(S))) busy,
+      Future<void> Function(void Function(S)) closure) {
+    singleFuture(
+        this,
+        () async => busy((emit) async {
+              do {
+                _more = false;
+                await closure(emit);
+
+                // See if another update was requested
+              } while (_more);
+            }), onBusy: () {
+      // Keep this state until we process again
+      _more = true;
+    });
+  }
+
+  bool _more = false;
+}