From a83011a332b79416348c5a531e28ff8c32e342a6 Mon Sep 17 00:00:00 2001
From: overtorment <overtorment@gmail.com>
Date: Tue, 28 May 2024 19:40:14 +0100
Subject: [PATCH] add: method to validate SP payment code

---
 src/index.ts                 | 14 ++++++++++++++
 tests/silent-payment.test.ts | 15 +++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/src/index.ts b/src/index.ts
index c60b1f0..7898e34 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -183,4 +183,18 @@ export class SilentPayment {
 
     return ret
   }
+
+  static isPaymentCodeValid(pc: string) {
+    try {
+      const result = bech32m.decode(pc, 118);
+      const version = result.words.shift();
+      if (version !== 0) {
+        return false;
+      }
+    } catch (_) {
+      return false;
+    }
+
+    return true;
+  }
 }
diff --git a/tests/silent-payment.test.ts b/tests/silent-payment.test.ts
index cdb4d2e..88a41d7 100644
--- a/tests/silent-payment.test.ts
+++ b/tests/silent-payment.test.ts
@@ -157,3 +157,18 @@ it("SilentPayment._ser32() works", () => {
   assert.strictEqual(SilentPayment._ser32(1).toString("hex"), "00000001");
   assert.strictEqual(SilentPayment._ser32(444).toString("hex"), "000001bc");
 });
+
+it("can validate payment code", () => {
+  assert.ok(SilentPayment.isPaymentCodeValid("sp1qqgste7k9hx0qftg6qmwlkqtwuy6cycyavzmzj85c6qdfhjdpdjtdgqjuexzk6murw56suy3e0rd2cgqvycxttddwsvgxe2usfpxumr70xc9pkqwv"));
+  assert.ok(SilentPayment.isPaymentCodeValid("sp1qqgrz6j0lcqnc04vxccydl0kpsj4frfje0ktmgcl2t346hkw30226xqupawdf48k8882j0strrvcmgg2kdawz53a54dd376ngdhak364hzcmynqtn"));
+  assert.ok(SilentPayment.isPaymentCodeValid("sp1qqgste7k9hx0qftg6qmwlkqtwuy6cycyavzmzj85c6qdfhjdpdjtdgqjex54dmqmmv6rw353tsuqhs99ydvadxzrsy9nuvk74epvee55drs734pqq"));
+  assert.ok(SilentPayment.isPaymentCodeValid("sp1qqgste7k9hx0qftg6qmwlkqtwuy6cycyavzmzj85c6qdfhjdpdjtdgqsg59z2rppn4qlkx0yz9sdltmjv3j8zgcqadjn4ug98m3t6plujsq9qvu5n"));
+  assert.ok(SilentPayment.isPaymentCodeValid("sp1qqgste7k9hx0qftg6qmwlkqtwuy6cycyavzmzj85c6qdfhjdpdjtdgq7c2zfthc6x3a5yecwc52nxa0kfd20xuz08zyrjpfw4l2j257yq6qgnkdh5"));
+
+  assert.ok(!SilentPayment.isPaymentCodeValid("sp1qqgste7k9hx0qftg6qmwlkqtwuy6cycyavzmzj85c6qdfhjdpdjtdgq7c2zfthc6x3a5yecwc52nxa0kfd20xuz08zyrjpfw4l2j257yq6qgn")); // short a few symbols
+  assert.ok(!SilentPayment.isPaymentCodeValid("sp1qq")); // short a few symbols
+  assert.ok(!SilentPayment.isPaymentCodeValid("garbage"));
+  assert.ok(!SilentPayment.isPaymentCodeValid("sp2qqgste7k9hx0qftg6qmwlkqtwuy6cycyavzmzj85c6qdfhjdpdjtdgq7c2zfthc6x3a5yecwc52nxa0kfd20xuz08zyrjpfw4l2j257yq6qgnkdh5")); // wrong prefix
+  assert.ok(!SilentPayment.isPaymentCodeValid("qqgste7k9hx0qftg6qmwlkqtwuy6cycyavzmzj85c6qdfhjdpdjtdgqjuexzk6murw56suy3e0rd2cgqvycxttddwsvgxe2usfpxumr70xc9pkqwv")); // no prefix
+  assert.ok(!SilentPayment.isPaymentCodeValid("qqgste7k9hx0qftg6qmwlkqtwuy6cycyavzmzj85c6qdfhjdpdjtdgqjuexzk6murw56suy3e0rd2cgqvycxttddwsvgxe2usfpxumr70xc9pkqwv123")); // no prefix
+});