NWC: lookup_invoice, so BTCPay Server can connect

BTCPay's NWC connector requires get_info, make_invoice, lookup_invoice
and list_transactions; we never offered lookup_invoice, so it refused the
connection string.

- ArkManager.lnLookup answers lookup_invoice from wallet state (by hash or
  bolt11, either direction; pending/settled/expired/failed, preimage once
  claimed). A retry's several actions on one hash defer to the furthest.
- The open app pushes a pending receive along before answering, so a
  merchant polling sees it settle.
- The service worker now answers make_invoice and lookup_invoice too, and
  claims a paid invoice's HTLCs during the lookup: a BTCPay sale settles
  with the wallet closed. Its list_transactions reports receives as well.
- get_info and the 13194 info event list the new method.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Dmcrt9KyNDKVWFKnb8BREo

2 files changed, 22 insertions, 4 deletions

diff --git a/src/features/ark.js b/src/features/ark.js
index 67759c9..87bb5c9 100644
--- a/src/features/ark.js
+++ b/src/features/ark.js
@@ -3629,7 +3629,18 @@ export function arkFeature(ctx) {
     async arkMakeInvoice(amountSat, description) {
       const mgr = await connectArk();
       const a = await mgr.createLnInvoice(amountSat, description);
-      return { invoice: a.invoice, paymentHash: a.paymentHash, amountSat };
+      return { invoice: a.invoice, paymentHash: a.paymentHash, amountSat, expiresAt: a.expiresAt };
+    },
+    // NIP-47 lookup_invoice: a payment of ours by hash or bolt11. One that
+    // is still pending gets a push first (a receive whose HTLCs have
+    // arrived is claimed right here), so a merchant polling sees it settle.
+    async arkLnLookup(q) {
+      const mgr = await connectArk();
+      const found = mgr.lnLookup(q);
+      if (!found || found.state !== 'pending') return found;
+      const a = (mgr.state.actions || []).find((x) => x.paymentHash === found.payment_hash && x.type.startsWith('ln-'));
+      if (a) await Promise.race([mgr.driveLn(a.id).catch(() => {}), new Promise((r) => setTimeout(r, 8000))]);
+      return mgr.lnLookup(q);
     },
     arkMovements() { const s = arkStateNow(); return s ? (s.movements || []) : []; },
     // The wallet's reusable ark receive address (BIP-353 names publish it).
diff --git a/src/features/nwc.js b/src/features/nwc.js
index 4259207..9cf8d0b 100644
--- a/src/features/nwc.js
+++ b/src/features/nwc.js
@@ -40,7 +40,7 @@ const RES_KIND = 23195;
 const INFO_KIND = 13194;
 
 // What we can actually honour. No pay_keysend (Ark can't), no multi_pay.
-const METHODS = ['get_info', 'get_balance', 'pay_invoice', 'make_invoice', 'list_transactions'];
+const METHODS = ['get_info', 'get_balance', 'pay_invoice', 'make_invoice', 'lookup_invoice', 'list_transactions'];
 
 // Requests older than this are ignored — a relay replaying history must not
 // re-trigger payments.
@@ -461,12 +461,19 @@ export function nwcFeature(ctx) {
       const inv = await hook('arkMakeInvoice', sat, params.description || '');
       return {
         result: {
-          type: 'incoming', invoice: inv.invoice, payment_hash: inv.paymentHash,
+          type: 'incoming', state: 'pending', invoice: inv.invoice, payment_hash: inv.paymentHash,
           amount: sat * 1000, created_at: nowSec(), description: params.description || '',
+          expires_at: inv.expiresAt ? Math.floor(inv.expiresAt / 1000) : undefined,
         },
       };
     }
 
+    if (method === 'lookup_invoice') {
+      if (!params.payment_hash && !params.invoice) return errRes('OTHER', 'payment_hash or invoice required');
+      const tx = await hook('arkLnLookup', { paymentHash: params.payment_hash, invoice: params.invoice });
+      return tx ? { result: tx } : errRes('NOT_FOUND', 'invoice not found');
+    }
+
     if (method === 'list_transactions') {
       const movements = hook('arkMovements') || [];
       const txs = movements
@@ -474,7 +481,7 @@ export function nwcFeature(ctx) {
         .slice(-(params.limit || 20))
         .map((m) => ({
           type: m.type === 'ln-receive' ? 'incoming' : 'outgoing',
-          invoice: m.invoice || '', preimage: m.preimage || '',
+          state: 'settled', invoice: m.invoice || '', preimage: m.preimage || '',
           amount: (m.amountSat || 0) * 1000, fees_paid: 0,
           created_at: Math.floor((m.ts || Date.now()) / 1000),
           settled_at: Math.floor((m.ts || Date.now()) / 1000),