From 372036ce20ac7f103dea05bae7e8686858d096a4 Mon Sep 17 00:00:00 2001
From: Lucas Fernandes Nogueira <lucasfernandesnog@gmail.com>
Date: Tue, 23 Feb 2021 21:31:15 -0300
Subject: [PATCH] refactor(api): move event's `once` to its own function
 (#1276)

---
 .changes/js-event-once.md |  5 +++++
 api/src/event.ts          |  2 +-
 api/src/helpers/event.ts  | 38 +++++++++++++++++++++++++++++---------
 api/src/window.ts         | 21 ++++++++++++++++-----
 4 files changed, 51 insertions(+), 15 deletions(-)
 create mode 100644 .changes/js-event-once.md

diff --git a/.changes/js-event-once.md b/.changes/js-event-once.md
new file mode 100644
index 000000000..ecd847cc4
--- /dev/null
+++ b/.changes/js-event-once.md
@@ -0,0 +1,5 @@
+---
+"tauri-api": minor
+---
+
+The event listener `once` kind was moved to a dedicated function.
diff --git a/api/src/event.ts b/api/src/event.ts
index 14572cfc0..640279e70 100644
--- a/api/src/event.ts
+++ b/api/src/event.ts
@@ -4,5 +4,5 @@ async function emit(event: string, payload?: string): Promise<void> {
   return emitEvent(event, undefined, payload)
 }
 
-export { listen } from './helpers/event'
+export { listen, once } from './helpers/event'
 export { emit }
diff --git a/api/src/helpers/event.ts b/api/src/helpers/event.ts
index cd8cd8cd8..3f02315fb 100644
--- a/api/src/helpers/event.ts
+++ b/api/src/helpers/event.ts
@@ -7,16 +7,10 @@ export interface Event<T> {
 
 export type EventCallback<T> = (event: Event<T>) => void
 
-/**
- * listen to an event from the backend
- *
- * @param event the event name
- * @param handler the event handler callback
- */
-async function listen<T>(
+async function _listen<T>(
   event: string,
   handler: EventCallback<T>,
-  once = false
+  once: boolean
 ): Promise<void> {
   await invoke({
     __tauriModule: 'Event',
@@ -29,6 +23,32 @@ async function listen<T>(
   })
 }
 
+/**
+ * listen to an event from the backend
+ *
+ * @param event the event name
+ * @param handler the event handler callback
+ */
+async function listen<T>(
+  event: string,
+  handler: EventCallback<T>
+): Promise<void> {
+  return _listen(event, handler, false)
+}
+
+/**
+ * listen to an one-off event from the backend
+ *
+ * @param event the event name
+ * @param handler the event handler callback
+ */
+async function once<T>(
+  event: string,
+  handler: EventCallback<T>
+): Promise<void> {
+  return _listen(event, handler, true)
+}
+
 /**
  * emits an event to the backend
  *
@@ -51,4 +71,4 @@ async function emit(
   })
 }
 
-export { listen, emit }
+export { listen, once, emit }
diff --git a/api/src/window.ts b/api/src/window.ts
index 2d71dafb2..061971ea4 100644
--- a/api/src/window.ts
+++ b/api/src/window.ts
@@ -1,5 +1,5 @@
 import { invoke } from './tauri'
-import { EventCallback, emit, listen } from './helpers/event'
+import { EventCallback, emit, listen, once } from './helpers/event'
 
 interface WindowDef {
   label: string
@@ -33,14 +33,25 @@ class TauriWindow {
    *
    * @param event the event name
    * @param handler the event handler callback
-   * @param once unlisten after the first trigger if true
    */
   async listen<T>(
     event: string,
-    handler: EventCallback<T>,
-    once = false
+    handler: EventCallback<T>
   ): Promise<void> {
-    return listen(event, handler, once)
+    return listen(event, handler)
+  }
+
+  /**
+   * Listen to an one-off event emitted by the webview
+   *
+   * @param event the event name
+   * @param handler the event handler callback
+   */
+  async once<T>(
+    event: string,
+    handler: EventCallback<T>
+  ): Promise<void> {
+    return once(event, handler)
   }
 
   /**