From 967296a5a2200e931cee2f21ef42e72c17a354fb Mon Sep 17 00:00:00 2001
From: Kurt Preston <kpreston@drw.com>
Date: Wed, 23 Jun 2021 11:49:49 -0500
Subject: [PATCH] Implementing unsubscription queue for transactional removes

---
 src/strongbus.ts      | 34 +++++++++++++++++++++++++++++++---
 src/strongbus_spec.ts |  2 +-
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/src/strongbus.ts b/src/strongbus.ts
index 94697b8..057329e 100644
--- a/src/strongbus.ts
+++ b/src/strongbus.ts
@@ -66,6 +66,14 @@ export class Bus<TEventMap extends object = object> implements Scannable<TEventM
   private readonly bus = new Map<EventKeys<TEventMap>|Events.WILDCARD, Set<EventHandlers.GenericHandler>>();
   private readonly lifecycle = new Map<Lifecycle, Set<EventHandlers.GenericHandler>>();
 
+  // Queue of unsubscription requests so that they are processed transactionally in oprder
+  private readonly _unsubQueue: {
+    token: string;
+    event: EventKeys<TEventMap>|Events.WILDCARD;
+    handler: EventHandlers.GenericHandler;
+  }[] = [];
+  private _purgingUnsubQueue: boolean = false;
+
   constructor(options?: Options) {
     this.options = {
       ...Bus.defaultOptions,
@@ -426,13 +434,33 @@ export class Bus<TEventMap extends object = object> implements Scannable<TEventM
   private cacheListener(event: EventKeys<TEventMap>|Events.WILDCARD, handler: EventHandlers.GenericHandler): Events.Subscription {
     const token = randomId();
     const sub = generateSubscription(() => {
+      this._unsubQueue.push({
+        token,
+        event,
+        handler
+      });
+      this.purgeUnsubQueue();
+    });
+    this.subscriptionCache.set(token, sub);
+    return sub;
+  }
+
+  private purgeUnsubQueue() {
+    if(this._purgingUnsubQueue) {
+      return;
+    } else {
+      this._purgingUnsubQueue = true;
+    }
+
+    while(this._unsubQueue.length) {
+      const {token, event, handler} = this._unsubQueue.shift();
       if(this.subscriptionCache.has(token)) {
         this.subscriptionCache.delete(token);
         this.removeListener(event, handler);
       }
-    });
-    this.subscriptionCache.set(token, sub);
-    return sub;
+    }
+
+    this._purgingUnsubQueue = false;
   }
 
   private removeListener(event: EventKeys<TEventMap>|Events.WILDCARD, handler: EventHandlers.GenericHandler): void {
diff --git a/src/strongbus_spec.ts b/src/strongbus_spec.ts
index 4d8a769..df88916 100644
--- a/src/strongbus_spec.ts
+++ b/src/strongbus_spec.ts
@@ -641,7 +641,7 @@ describe('Strongbus.Bus', () => {
         expect(onActive).toHaveBeenCalledTimes(1);
       });
 
-      fit('handles unsubscribes fired from hooks', async () => {
+      it('handles unsubscribes fired from hooks', async () => {
         const sub1 = bus.on('foo', () => {});
         const sub2 = bus.on('foo', () => {});
         bus.hook('willRemoveListener', () => sub2());