nwc: fix make_invoice timestamps (ms -> seconds) breaking NWC clients

Port of master 0154bb06. generate() stores `created` in milliseconds, but
NWC make_invoice returned it directly as created_at and computed
expires_at = created_at + expiry. NWC timestamps are Unix SECONDS
(NIP-47), so clients parsed a ~1.78e12 expires_at that overflowed their
date types (ptcpay's .NET DateTimeOffset, issue #84). Convert created to
seconds. Fixes #84.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/nwc.ts b/lib/nwc.ts
index 2053ccb5..662d2fa8 100644
--- a/lib/nwc.ts
+++ b/lib/nwc.ts
@@ -341,7 +341,14 @@ const handle = (method, params, ev, app, user) =>
         expiry,
       };
 
-      const { hash, created: created_at, paymentHash } = await generate({ invoice, user });
+      const { hash, created, paymentHash } = await generate({ invoice, user });
+
+      // generate() stores `created` in milliseconds (Date.now()), but NWC
+      // timestamps are Unix SECONDS (NIP-47). Returning ms here produced an
+      // expires_at ~1.78e12 that overflowed clients' date parsers — e.g.
+      // ptcpay's .NET DateTimeOffset (issue #84: "Valid values are between
+      // -62135596800 and 253402300799"). Convert to seconds.
+      const created_at = Math.floor(created / 1000);
 
       return result({
         type: "incoming",