Add a RelayError class, improve relay error handling

src/controllers/nostr/relay.ts

@@ -15,12 +15,14 @@ import type { Event, Filter } from '@/deps.ts';
 /** Limit of events returned per-filter. */
 const FILTER_LIMIT = 100;
 
+/** NIP-01 relay to client message. */
 type RelayMsg =
   | ['EVENT', string, Event]
   | ['NOTICE', string]
   | ['EOSE', string]
   | ['OK', string, boolean, string];
 
+/** Set up the Websocket connection. */
 function connectStream(socket: WebSocket) {
   socket.onmessage = (e) => {
     const result = jsonSchema.pipe(clientMsgSchema).safeParse(e.data);
@@ -31,6 +33,7 @@ function connectStream(socket: WebSocket) {
     }
   };
 
+  /** Handle client message. */
   function handleMsg(msg: ClientMsg) {
     switch (msg[0]) {
       case 'REQ':
@@ -45,6 +48,7 @@ function connectStream(socket: WebSocket) {
     }
   }
 
+  /** Handle REQ. Start a subscription. */
   async function handleReq([_, sub, ...filters]: ClientREQ) {
     for (const event of await eventsDB.getFilters(prepareFilters(filters))) {
       send(['EVENT', sub, event]);
@@ -52,20 +56,28 @@ function connectStream(socket: WebSocket) {
     send(['EOSE', sub]);
   }
 
+  /** Handle EVENT. Store the event. */
   async function handleEvent([_, event]: ClientEVENT) {
     try {
+      // This will store it (if eligible) and run other side-effects.
       await pipeline.handleEvent(event);
       send(['OK', event.id, true, '']);
-    } catch (_e) {
-      send(['OK', event.id, false, 'blocked: only registered users can post']);
+    } catch (e) {
+      if (e instanceof pipeline.RelayError) {
+        send(['OK', event.id, false, e.message]);
+      } else {
+        send(['OK', event.id, false, 'error: something went wrong']);
+      }
     }
   }
 
+  /** Handle CLOSE. Close the subscription. */
   function handleClose([_, _sub]: ClientCLOSE) {
     // TODO: ???
     return;
   }
 
+  /** Send a message back to the client. */
   function send(msg: RelayMsg) {
     return socket.send(JSON.stringify(msg));
   }