Features phase 2b: silent payments + nostr sync leave the core wallet

wallet.js drops from 2,374 to ~1,970 lines, holding only BIP84 on-chain
logic plus generic feature seams. New seams added this pass:
  registerBalanceExtra   extra confirmed/pending buckets
  registerInputProvider  extra spendable inputs for buildTx
  registerSendPreparer   destinations needing post-selection derivation
  registerInputSigner    non-BIP84 input signing
  registerHistoryProvider / registerScanHook / registerRealtimeHook /
  registerLoadHook / registerCacheExtension / registerCacheSavedHook

src/features/sp-wallet.js: the whole BIP-352 engine — key derivation,
worker-accelerated indexer scanning, the live indexer WebSocket, SP
outputs as spendable inputs, sp1 send preparation, and per-output-key
signing — installs via those seams (installSpWallet).

src/features/sync.js: nostr identity + encrypted cross-device state sync
plus its Settings card, installed via load/cache-saved/realtime hooks.
profileChip/nostrProfile move here-adjacent (into gifts, the only other
nostr consumer), so core app.js no longer imports nostr at all.

buildTx/sign are now feature-agnostic (input providers + preparers +
signers); _recomputeBalance* use the balance-extra registry, so a core
build with no SP no longer calls a missing spBalance() (that regression
dropped the minimal build into offline mode — caught by the smoke test).

New coverage: tools/sp-test.js drives two browser "devices" through an
SP send, indexer discovery, and an SP-input spend on the ark regtest
chain (needs tools/sp-indexer.js pointed at bitcoind:18543). Minimal
smoke now also asserts no SP/nostr code ships.

Minimal profile: 314KB, down from 412KB (full: 580KB). All suites green:
minimal smoke, sp-test, ark UI, gift lifecycle.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01QFAcD4V284DvYZZHP7Rxxy

1 files changed, 119 insertions, 0 deletions

diff --git a/src/features/sync.js b/src/features/sync.js
new file mode 100644
index 0000000..8cbd9f3
--- /dev/null
+++ b/src/features/sync.js
@@ -0,0 +1,119 @@
+// Cross-device sync feature — encrypted wallet state on Nostr relays
+// (NIP-44 to self, replaceable kind 30078) plus the wallet's nostr identity
+// (used e.g. to DM locked-gift claim codes). Installed onto the core wallet;
+// a build without sync ships none of it and never talks to a relay.
+
+import { NostrSync, getSyncConfig, setSyncConfig, npubOf } from '../nostr.js';
+import { t } from '../i18n.js';
+
+export function installSyncWallet(wallet) {
+  if (wallet.syncFromNostr) return; // already installed
+  wallet.nostr = new NostrSync();
+  wallet._nostrPubTimer = null;
+
+  Object.assign(wallet, {
+    // Our nostr identity (used to DM a locked gift's claim code to the recipient).
+    nostrPubkey() { return (this.nostr && this.nostr.pk) || null; },
+
+    nostrNpub() { const pk = this.nostrPubkey(); return pk ? npubOf(pk) : null; },
+
+    // Send a nostr DM (e.g. a locked gift's claim code) to a recipient pubkey.
+    async sendNostrDM(recipientPkHex, text) {
+      return this.nostr && this.nostr.sk ? this.nostr.sendDM(recipientPkHex, text) : false;
+    },
+
+    // Pull the latest state from Nostr; apply it if it's newer than what we have.
+    // Returns true if state was applied (so the caller can skip a full scan).
+    async syncFromNostr() {
+      const sync = getSyncConfig();
+      if (this.offline || !sync.enabled) return false;
+      this.nostr.setRelays(sync.relays);
+      let remote;
+      try {
+        remote = await this.nostr.fetch();
+      } catch {
+        return false;
+      }
+      if (!remote) return false;
+      if ((remote.savedAt || 0) > (this._savedAt || 0)) {
+        this._applySnapshot(remote);
+        this.saveCache(); // mirror into localStorage
+        this.emit();
+        return true;
+      }
+      // Our local copy is newer (or equal) — push it up so the relay catches up.
+      if ((this._savedAt || 0) > (remote.savedAt || 0)) this.saveCache();
+      return true; // remote existed, so no full scan needed
+    },
+  });
+
+  // identity follows the open wallet
+  wallet.registerLoadHook(() => {
+    if (wallet.mnemonic) wallet.nostr.load(wallet.mnemonic, wallet.passphrase);
+    else wallet.nostr.unload();
+  });
+  // push every saved snapshot to the relays (debounced) unless sync is off
+  wallet.registerCacheSavedHook((snap) => {
+    const sync = getSyncConfig();
+    if (wallet.offline || !sync.enabled) return;
+    wallet.nostr.setRelays(sync.relays);
+    clearTimeout(wallet._nostrPubTimer);
+    wallet._nostrPubTimer = setTimeout(() => wallet.nostr.publish(snap), 2500);
+  });
+  wallet.registerRealtimeHook({ stop: () => clearTimeout(wallet._nostrPubTimer) });
+}
+
+export function syncFeature(ctx) {
+  const { h, ui, render, wallet } = ctx;
+  installSyncWallet(wallet);
+
+  // Cross-device sync settings: toggle + editable relay list (default coinos).
+  function syncCard() {
+    const cfg = getSyncConfig();
+    const setEnabled = (enabled) => {
+      if (enabled === cfg.enabled) return;
+      setSyncConfig({ enabled, relays: cfg.relays });
+      render();
+      // On enable, pull anything newer from the relays, then push our copy up.
+      if (enabled && !wallet.offline) {
+        wallet.syncFromNostr().catch(() => {}).finally(() => wallet.saveCache());
+      }
+    };
+    return h(
+      'div',
+      { class: 'card col' },
+      h('h3', {}, t('deviceSync')),
+      h('p', { class: 'small muted', style: 'margin:0' }, t('deviceSyncDesc')),
+      h('div', { class: 'row between' },
+        h('span', { class: 'lab', style: 'margin:0' }, t('syncAcross')),
+        h('div', { class: 'seg' },
+          h('button', { type: 'button', class: cfg.enabled ? 'active' : '', onClick: () => setEnabled(true) }, t('syncOn')),
+          h('button', { type: 'button', class: !cfg.enabled ? 'active' : '', onClick: () => setEnabled(false) }, t('syncOff'))
+        )
+      ),
+      cfg.enabled
+        ? h('label', { class: 'field' },
+            h('span', { class: 'lab' }, t('relaysLabel')),
+            h('textarea', {
+              placeholder: 'wss://relay.example.com',
+              autocapitalize: 'none', autocomplete: 'off', spellcheck: 'false',
+              style: 'min-height:64px',
+              value: cfg.relays.join('\n'),
+              onInput: (e) => {
+                const relays = e.target.value.split('\n').map((s) => s.trim()).filter(Boolean);
+                setSyncConfig({ enabled: true, relays });
+              },
+            }),
+            h('div', { class: 'small faint' }, t('relaysHint'))
+          )
+        : null
+    );
+  }
+
+  return {
+    id: 'sync',
+    settingsCards() {
+      return wallet.watchOnly || !wallet.mnemonic ? [] : [syncCard()];
+    },
+  };
+}