feat: nip-47 nwc wallet service engine with per-connection budgets

src/lnurlcash/nwc/transport.ts

@@ -0,0 +1,40 @@
+// The relay-facing transport for the NWC service, kept injectable so
+// tests never touch a network. Same pattern as nostr/transport.ts: the
+// default (nostr-tools' SimplePool) is imported lazily, so merely
+// importing the service module never opens (or even references) a
+// WebSocket.
+
+import type {Filter as NostrFilter} from 'nostr-tools/filter'
+
+import type {NostrEvent} from './protocol'
+
+export type {NostrFilter}
+
+export type NwcSubscription = {
+  close: () => void
+}
+
+export type NwcTransport = {
+  publish: (relays: string[], event: NostrEvent) => Promise<void>
+  subscribe: (
+    relays: string[],
+    filter: NostrFilter,
+    onEvent: (event: NostrEvent) => void
+  ) => NwcSubscription
+}
+
+export const defaultNwcTransport = async (): Promise<NwcTransport> => {
+  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 accepting is enough - same rule as the backup
+      if (!results.some(r => r.status === 'fulfilled')) {
+        throw new Error('No relay accepted the event.')
+      }
+    },
+    subscribe: (relays, filter, onEvent) =>
+      pool.subscribeMany(relays, filter, {onevent: onEvent})
+  }
+}