relay: `sub.events` async iterator

relay.test.ts

@@ -57,6 +57,19 @@ test('querying', async () => {
   expect(t2).toEqual(true)
 }, 10000)
 
+test('async iterator', async () => {
+  let sub = relay.sub([
+    {
+      ids: ['d7dd5eb3ab747e16f8d0212d53032ea2a7cadef53837e5a6c66d42849fcb9027'],
+    },
+  ])
+
+  for await (const event of sub.events) {
+    expect(event).toHaveProperty('id', 'd7dd5eb3ab747e16f8d0212d53032ea2a7cadef53837e5a6c66d42849fcb9027')
+    break
+  }
+})
+
 test('get()', async () => {
   let event = await relay.get({
     ids: ['d7dd5eb3ab747e16f8d0212d53032ea2a7cadef53837e5a6c66d42849fcb9027'],

relay.ts

@@ -39,6 +39,7 @@ export type Sub<K extends number = number> = {
   unsub: () => void
   on: <T extends keyof SubEvent<K>, U extends SubEvent<K>[T]>(event: T, listener: U) => void
   off: <T extends keyof SubEvent<K>, U extends SubEvent<K>[T]>(event: T, listener: U) => void
+  events: AsyncGenerator<Event<K>, void, unknown>
 }
 
 export type SubscriptionOptions = {
@@ -241,6 +242,47 @@ export function relayInit(
     }
     trySend([verb, subid, ...filters])
 
+    async function* eventsGenerator(): AsyncGenerator<Event<K>, void, unknown> {
+      let nextResolve: ((event: Event<K>) => void) | undefined
+      const eventQueue: Event<K>[] = []
+
+      const pushToQueue = (event: Event<K>) => {
+        if (nextResolve) {
+          nextResolve(event)
+          nextResolve = undefined
+        } else {
+          eventQueue.push(event)
+        }
+      }
+
+      // Register the event listener
+      if (!subListeners[subid]) {
+        subListeners[subid] = {
+          event: [],
+          count: [],
+          eose: []
+        }
+      }
+      subListeners[subid].event.push(pushToQueue)
+
+      try {
+        while (true) {
+          if (eventQueue.length > 0) {
+            yield eventQueue.shift()!
+          } else {
+            const event = await new Promise<Event<K>>((resolve) => {
+              nextResolve = resolve
+            })
+            yield event
+          }
+        }
+      } finally {
+        // Unregister the event listener when the generator is done
+        const idx = subListeners[subid].event.indexOf(pushToQueue)
+        if (idx >= 0) subListeners[subid].event.splice(idx, 1)
+      }
+    }
+
     return {
       sub: (newFilters, newOpts = {}) =>
         sub(newFilters || filters, {
@@ -266,6 +308,9 @@ export function relayInit(
         let idx = listeners[type].indexOf(cb)
         if (idx >= 0) listeners[type].splice(idx, 1)
       },
+      get events() {
+        return eventsGenerator()
+      }
     }
   }