1 files changed, 50 insertions, 0 deletions
diff --git a/src/clink.js b/src/clink.js
new file mode 100644
index 0000000..9f381c1
--- /dev/null
+++ b/src/clink.js
@@ -0,0 +1,50 @@
+// CLINK payer — ask an offer code's service for an invoice over nostr.
+// The counterpart of src/noffer.js (the codec) and the responder in
+// features/nwc.js: a NIP-44-encrypted kind-21001 request goes to the service
+// pubkey on the relay the code names, and {bolt11} (or {error}) comes back.
+
+import {
+  nip44, finalizeEvent, generateSecretKey, publishOn, subscribeOn,
+} from './nostr.js';
+
+const OFFER_KIND = 21001;
+
+// dest: a decoded noffer ({ pubkey, relay, offerId }). Signs with a throwaway
+// key, so paying reveals no identity to the service. amountSat may be omitted
+// for offers that price themselves (the returned invoice carries the amount).
+// Resolves the bolt11 string; rejects on a service error or silence.
+export function requestOfferInvoice(dest, { amountSat, description, timeoutMs = 12000 } = {}) {
+  return new Promise((resolve, reject) => {
+    const relays = [dest.relay].filter(Boolean);
+    if (!relays.length) return reject(new Error('offer code names no relay'));
+    const sk = generateSecretKey();
+    const key = nip44.getConversationKey(sk, dest.pubkey);
+    const payload = { offer: dest.offerId || '' };
+    if (amountSat) payload.amount_sats = Math.floor(amountSat);
+    if (description) payload.description = String(description).slice(0, 100);
+    const req = finalizeEvent({
+      kind: OFFER_KIND, created_at: Math.floor(Date.now() / 1000),
+      tags: [['p', dest.pubkey], ['clink_version', '1']],
+      content: nip44.encrypt(JSON.stringify(payload), key),
+    }, sk);
+    let done = false;
+    let close = () => {};
+    const finish = (err, bolt11) => {
+      if (done) return;
+      done = true;
+      clearTimeout(timer);
+      close();
+      err ? reject(err) : resolve(bolt11);
+    };
+    const timer = setTimeout(() => finish(new Error('the recipient’s service did not answer')), timeoutMs);
+    // subscribe before publishing — a fast service can answer within the RTT
+    close = subscribeOn(relays, { kinds: [OFFER_KIND], '#e': [req.id], since: Math.floor(Date.now() / 1000) - 5 }, (ev) => {
+      try {
+        const body = JSON.parse(nip44.decrypt(ev.content, key));
+        if (body.bolt11) return finish(null, body.bolt11);
+        if (body.error) return finish(new Error(body.error));
+      } catch {}
+    });
+    publishOn(relays, req).catch(() => {});
+  });
+}