feat(core/relays): implement reconnection logic

core/relays.ts

@@ -1,9 +1,11 @@
 import type { Stringified } from "./types.ts";
 import type {
   ClientToRelayMessage,
+  EventId,
   EventKind,
   NostrEvent,
   RelayToClientMessage,
+  RelayToClientMessageType,
   RelayUrl,
   SubscriptionFilter,
   SubscriptionId,
@@ -97,6 +99,13 @@
     );
   }
 
+  dispatch<T extends RelayEventType>(
+    type: T,
+    data: RelayEventTypeRecord[T],
+  ): void {
+    this.dispatchEvent(new RelayEvent(type, data));
+  }
+
   subscribe<K extends EventKind>(
     filter: SubscriptionFilter<K> | SubscriptionFilter<K>[],
     options: Partial<SubscriptionOptions> = {},
@@ -108,19 +117,21 @@
       filters: [filter].flat(),
       options,
     };
+    const resubscribe = () => this.dispatch("resubscribe", { ...context });
     return new ReadableStream<NostrEvent<K>>({
       start: (controller) => {
-        this.dispatchEvent(
-          new RelayEvent("subscribe", { ...context, controller }),
+        this.addEventListener(
+          context.id,
+          () => this.ws.removeEventListener("close", resubscribe),
         );
+        this.dispatch("subscribe", { ...context, controller });
       },
-      pull: (controller) => {
-        this.dispatchEvent(new RelayEvent("pull", { ...context, controller }));
+      pull: () => {
+        this.ws.addEventListener("close", resubscribe, { once: true });
+        this.ws.ready();
       },
       cancel: (reason) => {
-        this.dispatchEvent(
-          new RelayEvent("unsubscribe", { ...context, reason }),
-        );
+        this.dispatch("unsubscribe", { ...context, reason });
       },
     }, new CountQueuingStrategy({ highWaterMark: options.nbuffer }));
   }
@@ -133,9 +144,7 @@
    */
   publish<K extends EventKind>(event: NostrEvent<K>): Promise<void> {
     return new Promise<void>((resolve, reject) => {
-      this.dispatchEvent(
-        new RelayEvent("publish", { event, resolve, reject }),
-      );
+      this.dispatch("publish", { event, resolve, reject });
       this.ws.addEventListener(
         "close",
         () => reject(new ConnectionClosed()),
@@ -183,12 +192,25 @@
   reject: (reason: unknown) => void;
 }
 
+type SubscriptionMessage = {
+  [T in RelayToClientMessageType]: RelayToClientMessage<T>[1] extends
+    SubscriptionId ? RelayToClientMessage<T> : never;
+}[RelayToClientMessageType];
+
+type PublicationMessage = {
+  [T in RelayToClientMessageType]: RelayToClientMessage<T>[1] extends EventId
+    ? RelayToClientMessage<T>
+    : never;
+}[RelayToClientMessageType];
+
 export interface RelayEventTypeRecord {
   message: RelayToClientMessage;
   subscribe: SubscriptionContextWithController;
-  pull: SubscriptionContextWithController;
+  resubscribe: SubscriptionContext;
   unsubscribe: SubscriptionContextWithReason;
   publish: PublicationContext;
+  [id: SubscriptionId]: SubscriptionMessage;
+  [id: EventId]: PublicationMessage;
 }
 
 export type RelayEventType = keyof RelayEventTypeRecord;

core/websockets.ts

@@ -23,6 +23,7 @@ type EventListenerOptionsMap = Map<
  */
 export class LazyWebSocket implements WebSocketLike {
   #ws?: WebSocket;
+  readonly #ac = new AbortController();
   readonly #createWebSocket: () => WebSocket;
   readonly #eventListenerMap = new Map<
     WebSocketEventType,
@@ -86,6 +87,7 @@ export class LazyWebSocket implements WebSocketLike {
     if (!this.#ws) {
       return;
     }
+    this.#ac.abort();
     switch (this.#ws.readyState) {
       case WebSocket.CONNECTING:
         await this.#once("open");
@@ -111,6 +113,8 @@ export class LazyWebSocket implements WebSocketLike {
     listener: EventListenerOrEventListenerObject,
     options: boolean | AddEventListenerOptions = {},
   ) => {
+    options = typeof options === "boolean" ? { capture: options } : options;
+    options = { signal: this.#ac.signal, ...options };
     this.#ws?.addEventListener(type, listener, options);
     const map = this.#eventListenerMap.get(type);
     if (map) {

lib/testing.ts

@@ -1,16 +1,24 @@
 type MessageEventData = string | ArrayBufferLike | Blob | ArrayBufferView;
 
 export class MockWebSocket extends EventTarget implements WebSocket {
+  /**
+   * A list of all instances of MockWebSocket.
+   * An instance is removed from this list when it is closed.
+   */
   static get instances(): MockWebSocket[] {
-    return this.#instances;
+    return Array.from(this.#instances);
+  }
+  static #instances = new Set<MockWebSocket>();
+
+  static get first(): MockWebSocket | undefined {
+    return this.instances[0];
   }
-  static #instances: MockWebSocket[] = [];
 
   constructor(url?: string | URL, protocols?: string | string[]) {
     super();
     this.url = url?.toString() ?? "";
     this.protocol = protocols ? [...protocols].flat()[0] : "";
-    MockWebSocket.#instances.push(this);
+    MockWebSocket.#instances.add(this);
     // Simulate async behavior of WebSocket as much as possible.
     queueMicrotask(() => {
       this.#readyState = 1;
@@ -50,9 +58,11 @@
       if (this.#remote) {
         this.#remote.#readyState = 3;
         this.#remote.dispatchEvent(new CloseEvent("close", { code, reason }));
+        MockWebSocket.#instances.delete(this.#remote);
       }
       this.#readyState = 3;
       this.dispatchEvent(new CloseEvent("close", { code, reason }));
+      MockWebSocket.#instances.delete(this);
     });
   }
 

nips/01/relays.ts

@@ -1,35 +1,5 @@
-import type {
-  EventId,
-  RelayToClientMessage,
-  RelayToClientMessageType,
-  SubscriptionId,
-} from "../../core/protocol.d.ts";
 import { EventRejected, RelayEvent, RelayModule } from "../../core/relays.ts";
 
-type SubscriptionMessage = {
-  [T in RelayToClientMessageType]: RelayToClientMessage<T>[1] extends
-    SubscriptionId ? RelayToClientMessage<T> : never;
-}[RelayToClientMessageType];
-
-type PublicationMessage = {
-  [T in RelayToClientMessageType]: RelayToClientMessage<T>[1] extends EventId
-    ? RelayToClientMessage<T>
-    : never;
-}[RelayToClientMessageType];
-
-type ExtentionalEventTypeRecord =
-  & {
-    [id in SubscriptionId]: SubscriptionMessage;
-  }
-  & {
-    [id in EventId]: PublicationMessage;
-  };
-
-declare module "../../core/relays.ts" {
-  // deno-lint-ignore no-empty-interface
-  interface RelayEventTypeRecord extends ExtentionalEventTypeRecord {}
-}
-
 export class SubscriptionClosed extends Error {}
 
 const install: RelayModule["default"] = (relay) => {
@@ -65,11 +35,14 @@
         }
       }
     });
-    return relay.send(["REQ", id, ...filters]);
+    relay.send(["REQ", id, ...filters]);
+  });
+  relay.addEventListener("resubscribe", ({ data: { id, filters } }) => {
+    relay.send(["REQ", id, ...filters]);
   });
   relay.addEventListener("unsubscribe", ({ data: { id } }) => {
     if (relay.status === WebSocket.OPEN) {
-      return relay.send(["CLOSE", id]);
+      relay.send(["CLOSE", id]);
     }
   });
   relay.addEventListener("publish", (ev) => {

nips/01/relays_test.ts

@@ -20,7 +20,11 @@ import {
 } from "../../core/relays.ts?nips=1";
 import { SubscriptionClosed } from "../../nips/01/relays.ts";
 
-describe("NIP-01/Relay", () => {
+function getRemoteSocket() {
+  return MockWebSocket.instances[0].remote;
+}
+
+describe("Relay (NIP-01)", () => {
   const url = "wss://localhost:8080";
   let relay: Relay;
   let sub_0: ReadableStream<NostrEvent<0>>;
@@ -30,6 +34,7 @@ describe("NIP-01/Relay", () => {
     globalThis.WebSocket = MockWebSocket;
     relay = new Relay(url);
   });
+
   afterAll(() => {
     if (relay.status === WebSocket.OPEN) {
       return relay.close();
@@ -39,33 +44,33 @@ describe("NIP-01/Relay", () => {
   it("should have loaded NIP-01 module", () => {
     assertEquals(relay.config.modules.length, 1);
   });
+
   it("should create a subscription", () => {
     sub_1 = relay.subscribe({ kinds: [1] }, { id: "test-1" });
     assertInstanceOf(sub_1, ReadableStream);
   });
+
   it("should receive text notes", async () => {
     const reader = sub_1.getReader();
     const read = reader.read();
-    MockWebSocket.instances[0].remote.send(
-      JSON.stringify(["EVENT", "test-1", { kind: 1 }]),
-    );
+    getRemoteSocket().send(JSON.stringify(["EVENT", "test-1", { kind: 1 }]));
     const { value, done } = await read;
     assert(!done);
     assertEquals(value.kind, 1);
     reader.releaseLock();
   });
+
   it("should be able to open multiple subscriptions", () => {
-    sub_0 = relay.subscribe({ kinds: [0], limit: 1 }, {
-      id: "test-0",
-    });
+    sub_0 = relay.subscribe({ kinds: [0] }, { id: "test-0" });
     assert(sub_0 instanceof ReadableStream);
   });
+
   it("should recieve metas and notes simultaneously", async () => {
     const reader_0 = sub_0.getReader();
     const reader_1 = sub_1.getReader();
-    const ws = MockWebSocket.instances[0];
-    ws.remote.send(JSON.stringify(["EVENT", "test-0", { kind: 0 }]));
-    ws.remote.send(JSON.stringify(["EVENT", "test-1", { kind: 1 }]));
+    const remote = getRemoteSocket();
+    remote.send(JSON.stringify(["EVENT", "test-0", { kind: 0 }]));
+    remote.send(JSON.stringify(["EVENT", "test-1", { kind: 1 }]));
     const [{ value: value_0 }, { value: value_1 }] = await Promise.all([
       reader_0.read(),
       reader_1.read(),
@@ -77,18 +82,54 @@ describe("NIP-01/Relay", () => {
     reader_0.releaseLock();
     reader_1.releaseLock();
   });
+
+  it("should close a subscription with an error when receiving a CLOSED message", async () => {
+    getRemoteSocket().send(JSON.stringify(
+      [
+        "CLOSED",
+        "test-1" as SubscriptionId,
+        "error: test",
+      ] satisfies RelayToClientMessage<"CLOSED">,
+    ));
+    const reader = sub_1.getReader();
+    try {
+      await reader.read();
+    } catch (e) {
+      assertInstanceOf(e, SubscriptionClosed);
+      assertEquals(e.message, "error: test");
+    } finally {
+      reader.releaseLock();
+    }
+  });
+
+  it("should reconnect if connection is closed while waiting for an event", async () => {
+    const reader = sub_0.getReader();
+    const read = reader.read();
+    getRemoteSocket().close();
+    const reconnected = new Promise<true>((resolve) => {
+      relay.ws.addEventListener("open", () => resolve(true));
+    });
+    assert(await reconnected);
+    // We must use a new instance of MockWebSocket.
+    getRemoteSocket().send(JSON.stringify(["EVENT", "test-0", { kind: 0 }]));
+    const { value, done } = await read;
+    assert(!done);
+    assertEquals(value.kind, 0);
+    reader.releaseLock();
+  });
+
   it("should publish an event and recieve an accepting OK message", async () => {
     const eid = "test-true" as EventId;
-    const ws = MockWebSocket.instances[0];
+    const remote = getRemoteSocket();
     const arrived = new Promise<true>((resolve) => {
-      ws.remote.addEventListener(
+      remote.addEventListener(
         "message",
         (ev: MessageEvent<string>) => {
           // deno-fmt-ignore
           const [, event] = JSON.parse(ev.data) as ClientToRelayMessage<"EVENT">;
           if (event.id === eid) {
             assertEquals(event.kind, 1);
-            ws.remote.send(
+            remote.send(
               JSON.stringify(
                 ["OK", eid, true, ""] satisfies RelayToClientMessage<"OK">,
               ),
@@ -102,21 +143,22 @@ describe("NIP-01/Relay", () => {
     await relay.publish({ id: eid, kind: 1 } as any);
     assert(await arrived);
   });
+
   it("should receieve a rejecting OK message and throw EventRejected", async () => {
     const eid = "test-false" as EventId;
     // deno-fmt-ignore
     const msg = ["OK", eid, false, "error: test"] satisfies RelayToClientMessage<"OK">
-    const ws = MockWebSocket.instances[0];
+    const remote = getRemoteSocket();
     const arrived = new Promise<true>((resolve) => {
-      ws.remote.addEventListener(
+      remote.addEventListener(
         "message",
         (ev: MessageEvent<string>) => {
           // deno-fmt-ignore
           const [, event] = JSON.parse(ev.data) as ClientToRelayMessage<"EVENT">;
           if (event.id === eid) {
             assertEquals(event.kind, 1);
             resolve(true);
-            ws.remote.send(JSON.stringify(msg));
+            remote.send(JSON.stringify(msg));
           }
         },
       );
@@ -132,26 +174,16 @@ describe("NIP-01/Relay", () => {
     }
     await arrived;
   });
+
   it("should throw ConnectionClosed when connection is closed before recieving an OK message", async () => {
     const event = { id: "test-close" as EventId, kind: 1 };
     // deno-lint-ignore no-explicit-any
     const published = relay.publish(event as any).catch((e) => e);
-    MockWebSocket.instances[0].remote.close();
-    assertInstanceOf(await published, ConnectionClosed);
-  });
-  it("should close a subscription with an error when receiving a CLOSED message", async () => {
-    MockWebSocket.instances[0].remote.send(JSON.stringify(
-      [
-        "CLOSED",
-        "test-1" as SubscriptionId,
-        "error: test",
-      ] satisfies RelayToClientMessage<"CLOSED">,
-    ));
+    getRemoteSocket().close();
     try {
-      await sub_1.getReader().read();
+      await published;
     } catch (e) {
-      assertInstanceOf(e, SubscriptionClosed);
-      assertEquals(e.message, "error: test");
+      assertInstanceOf(e, ConnectionClosed);
     }
   });
 });