From 842b06460e5a79acf9319e6de8be7e62d884ea00 Mon Sep 17 00:00:00 2001
From: ethicnology <ethicnology@pm.me>
Date: Mon, 20 Jan 2025 14:31:31 -0500
Subject: [PATCH] feat: NIP21

---
 README.md                   |  1 +
 lib/nostr.dart              |  1 +
 lib/src/nips/nip_021.dart   | 19 +++++++++++++++++++
 test/nips/nip_021_test.dart | 34 ++++++++++++++++++++++++++++++++++
 4 files changed, 55 insertions(+)
 create mode 100644 lib/src/nips/nip_021.dart
 create mode 100644 test/nips/nip_021_test.dart

diff --git a/README.md b/README.md
index 1115c88..fff9e14 100644
--- a/README.md
+++ b/README.md
@@ -24,6 +24,7 @@ flutter pub add nostr
 - [x] [NIP 15 End of Stored Events Notice](https://github.com/nostr-protocol/nips/blob/master/15.md)
 - [x] [NIP 19 bech32-encoded entities](https://github.com/nostr-protocol/nips/blob/master/19.md)
 - [x] [NIP 20 Command Results](https://github.com/nostr-protocol/nips/blob/master/20.md)
+- [x] [NIP 21 nostr: URI scheme](https://github.com/nostr-protocol/nips/blob/master/21.md)
 - [x] [NIP 28 Public Chat](https://github.com/nostr-protocol/nips/blob/master/28.md)
 - [x] [NIP 50 Search Capability](https://github.com/nostr-protocol/nips/blob/master/50.md)
 - [x] [NIP 51 Lists](https://github.com/nostr-protocol/nips/blob/master/51.md)
diff --git a/lib/nostr.dart b/lib/nostr.dart
index 23c1587..c86e195 100644
--- a/lib/nostr.dart
+++ b/lib/nostr.dart
@@ -20,5 +20,6 @@ export 'src/nips/nip_010.dart';
 export 'src/nips/nip_013.dart';
 export 'src/nips/nip_019.dart';
 export 'src/nips/nip_020.dart';
+export 'src/nips/nip_021.dart';
 export 'src/nips/nip_028.dart';
 export 'src/nips/nip_051.dart';
diff --git a/lib/src/nips/nip_021.dart b/lib/src/nips/nip_021.dart
new file mode 100644
index 0000000..fe986bd
--- /dev/null
+++ b/lib/src/nips/nip_021.dart
@@ -0,0 +1,19 @@
+/// A utility class to handle Nostr URIs according to NIP-21 specification.
+/// Provides encode, decode functionalities for Nostr URIs.
+class NIP21 {
+  static const String _prefix = 'nostr:';
+
+  /// Parses a `nostr:` URI and extracts the identifier.
+  ///
+  /// Throws an [Exception] if the prefix `nostr:` is missing
+  static String decode(String uri) {
+    if (!uri.startsWith(_prefix)) {
+      throw Exception('Invalid Nostr URI: must start with "nostr:"');
+    }
+
+    return uri.substring(_prefix.length);
+  }
+
+  /// Generates a `nostr:` URI from a given content
+  static String encode(String content) => _prefix + content;
+}
diff --git a/test/nips/nip_021_test.dart b/test/nips/nip_021_test.dart
new file mode 100644
index 0000000..8c90c72
--- /dev/null
+++ b/test/nips/nip_021_test.dart
@@ -0,0 +1,34 @@
+import 'package:nostr/nostr.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('NIP21 URI Tests', () {
+    test('Parse valid npub URI', () {
+      expect(
+          NIP21.decode(
+              'nostr:npub1sn0wdenkukak0d9dfczzeacvhkrgz92ak56egt7vdgzn8pv2wfqqhrjdv9'),
+          equals(
+              'npub1sn0wdenkukak0d9dfczzeacvhkrgz92ak56egt7vdgzn8pv2wfqqhrjdv9'));
+    });
+
+    test('Parse valid nprofile URI', () {
+      expect(
+          NIP21.decode(
+              'nostr:nprofile1qqsrhuxx8l9ex335q7he0f09aej04zpazpl0ne2cgukyawd24mayt8gpp4mhxue69uhhytnc9e3k7mgpz4mhxue69uhkg6nzv9ejuumpv34kytnrdaksjlyr9p'),
+          equals(
+              'nprofile1qqsrhuxx8l9ex335q7he0f09aej04zpazpl0ne2cgukyawd24mayt8gpp4mhxue69uhhytnc9e3k7mgpz4mhxue69uhkg6nzv9ejuumpv34kytnrdaksjlyr9p'));
+    });
+
+    test('Generate npub URI', () {
+      expect(
+          NIP21.encode(
+              'npub1sn0wdenkukak0d9dfczzeacvhkrgz92ak56egt7vdgzn8pv2wfqqhrjdv9'),
+          equals(
+              'nostr:npub1sn0wdenkukak0d9dfczzeacvhkrgz92ak56egt7vdgzn8pv2wfqqhrjdv9'));
+    });
+
+    test('Invalid Nostr URI parsing', () {
+      expect(() => NIP21.decode('noprefix'), throwsA(isA<Exception>()));
+    });
+  });
+}