feat: add EOSE class to obtain subscriptionId (#41)

* added EOSE class

* added tests

* Message.deserialize handle EOSE

lib/nostr.dart

@@ -4,6 +4,7 @@
 library nostr;
 
 export 'src/event.dart';
+export 'src/eose.dart';
 export 'src/keychain.dart';
 export 'src/request.dart';
 export 'src/filter.dart';

lib/src/eose.dart

@@ -0,0 +1,26 @@
+import 'dart:convert';
+
+/// Indicates "end of stored events"
+///
+/// this class is mostly for getting subscription id
+class Eose {
+  /// default constructor
+  Eose(this.subscriptionId);
+
+  /// subscription_id is a random string that should be used to represent a subscription.
+  final String subscriptionId;
+
+  /// Serialize to nostr close message
+  /// - ["EOSE", subscription_id]
+  String serialize() {
+    return jsonEncode(["EOSE", subscriptionId]);
+  }
+
+  /// Deserialize a nostr close message
+  /// - ["CLOSE", subscription_id]
+  factory Eose.deserialize(input) {
+    if (input is! List<dynamic>) throw 'Invalid type for EOSE message';
+    if (input.length != 2) throw 'Invalid length for EOSE message';
+    return Eose(input[1]);
+  }
+}

lib/src/message.dart

@@ -32,6 +32,9 @@ class Message {
       case MessageType.close:
         message = Close.deserialize(data);
         break;
+      case MessageType.eose:
+        message = Eose.deserialize(data);
+        break;
       default:
         message = jsonEncode(data.sublist(1));
         break;

test/eose_test.dart

@@ -0,0 +1,26 @@
+import 'package:nostr/nostr.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('Eose', () {
+    test('Constructor', () {
+      String subscriptionId = generate64RandomHexChars();
+      var eose = Eose(subscriptionId);
+      expect(eose.subscriptionId, subscriptionId);
+    });
+
+    test('Eose.serialize', () {
+      String subscriptionId = generate64RandomHexChars();
+      String serialized = '["EOSE","$subscriptionId"]';
+      var eose = Eose(subscriptionId);
+      expect(eose.serialize(), serialized);
+    });
+
+    test('Eose.deserialize', () {
+      String subscriptionId = generate64RandomHexChars();
+      var serialized = ["EOSE", subscriptionId];
+      var eose = Eose.deserialize(serialized);
+      expect(eose.subscriptionId, subscriptionId);
+    });
+  });
+}

test/message_test.dart

@@ -35,6 +35,7 @@ void main() {
       String payload = '["EOSE", "random"]';
       var msg = Message.deserialize(payload);
       expect(msg.type, "EOSE");
+      expect(msg.message.subscriptionId, "random");
     });
 
     test('OK', () {