feat: nostr kind-30078 backup engine with nip-44 self-encryption and merge-on-restore

src/lnurlcash/nostr/transport.ts

@@ -0,0 +1,32 @@
+// The relay-facing transport for nostr backup, kept injectable so tests
+// never touch a network. The default is nostr-tools' SimplePool, imported
+// lazily: merely importing the backup module must never open (or even
+// reference) a WebSocket.
+
+import type {Filter as NostrFilter} from 'nostr-tools/filter'
+
+import type {NostrEvent} from './events'
+
+export type {NostrFilter}
+
+// publish throws when the event was accepted NOWHERE
+export type BackupTransport = {
+  publish: (relays: string[], event: NostrEvent) => Promise<void>
+  fetch: (relays: string[], filter: NostrFilter) => Promise<NostrEvent[]>
+}
+
+export const defaultTransport = async (): Promise<BackupTransport> => {
+  const {SimplePool} = await import('nostr-tools/pool')
+  const pool = new SimplePool()
+  return {
+    publish: async (relays, event) => {
+      const results = await Promise.allSettled(pool.publish(relays, event))
+      // one honest relay keeping the event is enough - addressable events
+      // are re-publishable, and the next debounced publish retries anyway
+      if (!results.some(r => r.status === 'fulfilled')) {
+        throw new Error('No relay accepted the backup event.')
+      }
+    },
+    fetch: (relays, filter) => pool.querySync(relays, filter)
+  }
+}