refactor: isolate Nostr backup publishing transport

src/lnurlcash/nostr/publisher.ts

@@ -22,9 +22,7 @@ export type BackupPublisherOptions = {
   onError?: (error: unknown) => void
 }
 
-export const createBackupPublisher = (
-  options: BackupPublisherOptions
-): BackupPublisher => {
+export const createBackupPublisher = (options: BackupPublisherOptions): BackupPublisher => {
   let timer: ReturnType<typeof setTimeout> | null = null
   let pending: Partial<BackupPartPayload> | null = null
   let running: Promise<void> | null = null
@@ -45,7 +43,9 @@ export const createBackupPublisher = (
       try {
         await options.publish(snapshot)
       } catch (error) {
-        options.onError?.(error)
+        options.onError?.(
+          error instanceof Error ? error : new Error('Backup publication failed.', {cause: error}),
+        )
       }
     }
   }
@@ -61,7 +61,7 @@ export const createBackupPublisher = (
   }
 
   return {
-    schedule: parts => {
+    schedule: (parts) => {
       pending = parts
       clearTimer()
       timer = setTimeout(() => void fire(), options.delayMs)
@@ -70,6 +70,6 @@ export const createBackupPublisher = (
     cancel: () => {
       clearTimer()
       pending = null
-    }
+    },
   }
 }

src/lnurlcash/nostr/transport.ts

@@ -23,10 +23,10 @@ export const defaultTransport = async (): Promise<BackupTransport> => {
       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')) {
+      if (!results.some((r) => r.status === 'fulfilled')) {
         throw new Error('No relay accepted the backup event.')
       }
     },
-    fetch: (relays, filter) => pool.querySync(relays, filter)
+    fetch: (relays, filter) => pool.querySync(relays, filter),
   }
 }

src/lnurlcash/nostrBackup.publisher.cases.ts

@@ -0,0 +1,211 @@
+// Nostr backup: key derivation stability, event build/parse round-trips,
+// tamper rejection, publish/fetch and restore against an in-memory relay
+// (the transport is injected - no network), and the debounced publisher.
+
+import {afterEach, beforeEach, describe, expect, it, vi} from 'vitest'
+import {bytesToHex} from '@noble/hashes/utils.js'
+import type {NostrEvent} from 'nostr-tools/core'
+import {finalizeEvent, getPublicKey} from 'nostr-tools/pure'
+import {v2 as nip44v2} from 'nostr-tools/nip44'
+import {buildNoteUrl} from 'lnurlcash-kit'
+
+import {deriveBearerAesKey, linkingPubKeyHex, saveLinkingKey} from './keys'
+import {
+  BACKUP_EVENT_KIND,
+  backupPubkey,
+  buildBackupEvent,
+  buildBackupEvents,
+  createBackupPublisher,
+  deriveBackupKey,
+  fetchBackup,
+  parseBackupEvent,
+  publishBackup,
+  restoreFromNostr,
+} from './nostrBackup'
+import type {BackupPartPayload, BackupTransport} from './nostrBackup'
+import {
+  loadBearers,
+  loadSettings,
+  mergeBearers,
+  persistBearer,
+  persistSettings,
+  readEncryptedBearers,
+} from './storage'
+import type {Bearer} from './types'
+import {addTrustedMint, isMintUnconfirmed, readTrustedMints} from './trustedMints'
+import {requiredValue, stubLocalStorage} from './test-utils'
+
+const LINKING_KEY = new Uint8Array(32).fill(7)
+const OTHER_KEY = new Uint8Array(32).fill(9)
+const OWNER_ID = linkingPubKeyHex(LINKING_KEY)
+
+const K1_A = 'aa'.repeat(32)
+const K1_B = 'bb'.repeat(32)
+const MINT_PUBKEY = 'ab'.repeat(33)
+
+// never connected - the recording transport below stands in for the relays
+const RELAYS = ['wss://relay-a.example', 'wss://relay-b.example']
+
+const bearerFixture = (overrides: Partial<Bearer> = {}): Bearer => ({
+  id: 'fixture',
+  url: buildNoteUrl('https://mint.example/w', K1_A, 21_000),
+  callback: 'https://mint.example/w/cb',
+  amount: 21_000,
+  verified: true,
+  createdAt: 1000,
+  updatedAt: 1000,
+  ...overrides,
+})
+
+// an in-memory relay set. It serves EVERY event it ever accepted, older
+// addressable copies included - like a relay that never replaces - which
+// is exactly the case fetchBackup's client-side latest-pick exists for
+const createRecordingTransport = (): {
+  transport: BackupTransport
+  events: NostrEvent[]
+} => {
+  const events: NostrEvent[] = []
+  const transport: BackupTransport = {
+    publish: (_relays, event) => {
+      events.push(event)
+      return Promise.resolve()
+    },
+    fetch: (_relays, filter) =>
+      Promise.resolve(
+        events.filter(
+          (e) =>
+            (!filter.kinds || filter.kinds.includes(e.kind)) &&
+            (!filter.authors || filter.authors.includes(e.pubkey)),
+        ),
+      ),
+  }
+  return {transport, events}
+}
+
+// flips the end of a base64 payload to different-but-valid characters
+const tamperContent = (content: string): string =>
+  content.slice(0, -4) + (content.endsWith('AAAA') ? 'BBBB' : 'AAAA')
+
+beforeEach(() => {
+  stubLocalStorage()
+})
+
+afterEach(() => {
+  vi.useRealTimers()
+})
+
+describe('createBackupPublisher', () => {
+  it('coalesces rapid schedules into a single publish of the latest snapshot', async () => {
+    vi.useFakeTimers()
+    const published: Partial<BackupPartPayload>[] = []
+    const publisher = createBackupPublisher({
+      publish: (p) => {
+        published.push(p)
+        return Promise.resolve()
+      },
+      delayMs: 1000,
+    })
+
+    publisher.schedule({settings: {defaultMint: 'a'}})
+    publisher.schedule({settings: {defaultMint: 'b'}})
+    publisher.schedule({settings: {defaultMint: 'c'}})
+    await vi.advanceTimersByTimeAsync(999)
+    expect(published).toEqual([])
+    await vi.advanceTimersByTimeAsync(1)
+    expect(published).toEqual([{settings: {defaultMint: 'c'}}])
+  })
+
+  it('publishes again when a change lands after the quiet window', async () => {
+    vi.useFakeTimers()
+    const published: Partial<BackupPartPayload>[] = []
+    const publisher = createBackupPublisher({
+      publish: (p) => {
+        published.push(p)
+        return Promise.resolve()
+      },
+      delayMs: 1000,
+    })
+
+    publisher.schedule({settings: {defaultMint: 'a'}})
+    await vi.advanceTimersByTimeAsync(1000)
+    publisher.schedule({settings: {defaultMint: 'b'}})
+    await vi.advanceTimersByTimeAsync(1000)
+    expect(published).toEqual([{settings: {defaultMint: 'a'}}, {settings: {defaultMint: 'b'}}])
+  })
+
+  it('publishes a snapshot that lands mid-publish instead of losing it', async () => {
+    vi.useFakeTimers()
+    const published: Partial<BackupPartPayload>[] = []
+    // the publish callback re-schedules on the publisher being created -
+    // a holder indirection keeps both const
+    const holder: {publisher?: ReturnType<typeof createBackupPublisher>} = {}
+    const publisher = createBackupPublisher({
+      publish: (p) => {
+        published.push(p)
+        // a local change lands while the first publish is in flight
+        if (published.length === 1) {
+          holder.publisher?.schedule({settings: {defaultMint: 'mid-flight'}})
+        }
+        return Promise.resolve()
+      },
+      delayMs: 1000,
+    })
+    holder.publisher = publisher
+
+    publisher.schedule({settings: {defaultMint: 'first'}})
+    await vi.advanceTimersByTimeAsync(1000)
+    expect(published).toEqual([
+      {settings: {defaultMint: 'first'}},
+      {settings: {defaultMint: 'mid-flight'}},
+    ])
+  })
+
+  it('flush publishes immediately; cancel drops the pending snapshot', async () => {
+    vi.useFakeTimers()
+    const published: Partial<BackupPartPayload>[] = []
+    const publisher = createBackupPublisher({
+      publish: (p) => {
+        published.push(p)
+        return Promise.resolve()
+      },
+      delayMs: 60_000,
+    })
+
+    publisher.schedule({settings: {defaultMint: 'a'}})
+    await publisher.flush()
+    expect(published).toEqual([{settings: {defaultMint: 'a'}}])
+
+    publisher.schedule({settings: {defaultMint: 'b'}})
+    publisher.cancel()
+    await vi.advanceTimersByTimeAsync(60_000)
+    expect(published).toHaveLength(1)
+  })
+
+  it('reports a failed publish via onError and retries on the next change', async () => {
+    vi.useFakeTimers()
+    const published: Partial<BackupPartPayload>[] = []
+    const errors: unknown[] = []
+    let failing = true
+    const publisher = createBackupPublisher({
+      publish: (p) => {
+        if (failing) return Promise.reject(new Error('relay down'))
+        published.push(p)
+        return Promise.resolve()
+      },
+      delayMs: 1000,
+      onError: (e) => {
+        errors.push(e)
+      },
+    })
+
+    publisher.schedule({settings: {defaultMint: 'a'}})
+    await vi.advanceTimersByTimeAsync(1000)
+    expect(published).toEqual([])
+    expect(errors).toHaveLength(1)
+
+    failing = false
+    publisher.schedule({settings: {defaultMint: 'b'}})
+    await vi.advanceTimersByTimeAsync(1000)
+    expect(published).toEqual([{settings: {defaultMint: 'b'}}])
+  })
+})