1 files changed, 40 insertions, 0 deletions
diff --git a/packages/taler-wallet-core/src/util/promiseUtils.ts b/packages/taler-wallet-core/src/util/promiseUtils.ts
index d152a12f4..bc1e40260 100644
--- a/packages/taler-wallet-core/src/util/promiseUtils.ts
+++ b/packages/taler-wallet-core/src/util/promiseUtils.ts
@@ -70,3 +70,43 @@ export class AsyncCondition {
     this.promCap = undefined;
   }
 }
+
+/**
+ * Flag that can be raised to notify asynchronous waiters.
+ *
+ * You can think of it as a promise that can
+ * be un-resolved.
+ */
+export class AsyncFlag {
+  private promCap?: OpenedPromise<void> = undefined;
+  private internalFlagRaised: boolean = false;
+
+  constructor() {}
+
+  /**
+   * Wait until the flag is raised.
+   *
+   * Reset if before returning.
+   */
+  wait(): Promise<void> {
+    if (this.internalFlagRaised) {
+      return Promise.resolve();
+    }
+    if (!this.promCap) {
+      this.promCap = openPromise<void>();
+    }
+    return this.promCap.promise;
+  }
+
+  raise(): void {
+    this.internalFlagRaised = true;
+    if (this.promCap) {
+      this.promCap.resolve();
+    }
+  }
+
+  reset(): void {
+    this.internalFlagRaised = false;
+    this.promCap = undefined;
+  }
+}