Display LN Address on "Receive via Lightning Address" page

lib/app/view/app.dart

@@ -52,8 +52,14 @@ class App extends StatelessWidget {
           lazy: false,
           create: (BuildContext context) => WebhookCubit(
             injector.breezSdkLiquid,
-            injector.breezPreferences,
-            injector.notifications,
+            WebhookService(
+              injector.breezSdkLiquid,
+              injector.notifications,
+            ),
+            LnUrlPayService(
+              injector.breezSdkLiquid,
+              injector.breezPreferences,
+            ),
           ),
         ),
         BlocProvider<CurrencyCubit>(

lib/cubit/webhook/lnurl_pay_service.dart

@@ -0,0 +1,172 @@
+import 'dart:convert';
+
+import 'package:breez_preferences/breez_preferences.dart';
+import 'package:breez_sdk_liquid/breez_sdk_liquid.dart';
+import 'package:flutter_breez_liquid/flutter_breez_liquid.dart';
+import 'package:http/http.dart' as http;
+import 'package:l_breez/cubit/webhook/webhook_state.dart';
+import 'package:logging/logging.dart';
+
+final Logger _logger = Logger('LnUrlPayService');
+
+class LnUrlPayService {
+  static const String lnurlServiceURL = 'https://breez.fun';
+
+  final BreezSDKLiquid _breezSdkLiquid;
+  final BreezPreferences _breezPreferences;
+
+  LnUrlPayService(this._breezSdkLiquid, this._breezPreferences);
+
+  Future<Map<String, String>> registerLnurlpay(
+    WalletInfo walletInfo,
+    String webhookUrl, {
+    String? username,
+  }) async {
+    final String pubKey = walletInfo.pubkey;
+
+    await _invalidatePreviousWebhookIfNeeded(pubKey, webhookUrl);
+
+    final int currentTime = DateTime.now().millisecondsSinceEpoch ~/ 1000;
+
+    // TODO(erdemyerebasmaz): Utilize user's username(only when user has created a new wallet)
+    // TODO(erdemyerebasmaz): Handle multiple device setup cases
+    final String? lnAddressUsername =
+        (username ?? await _breezPreferences.getProfileName())?.replaceAll(' ', '');
+
+    final SignMessageResponse? signMessageRes = await _generateSignature(
+      webhookUrl: webhookUrl,
+      currentTime: currentTime,
+      lnAddressUsername: lnAddressUsername,
+    );
+
+    if (signMessageRes == null) {
+      throw Exception('Missing signature');
+    }
+
+    final Map<String, String> response = await _postWebhookRegistrationRequest(
+      pubKey: pubKey,
+      webhookUrl: webhookUrl,
+      currentTime: currentTime,
+      lnAddressUsername: lnAddressUsername,
+      signature: signMessageRes.signature,
+    );
+
+    await setLnUrlPayKey(webhookUrl: webhookUrl);
+    return response;
+  }
+
+  Future<void> _invalidatePreviousWebhookIfNeeded(String pubKey, String webhookUrl) async {
+    final String? lastUsedLnurlPay = await getLnUrlPayKey();
+    if (lastUsedLnurlPay != null && lastUsedLnurlPay != webhookUrl) {
+      await _invalidateLnurlPay(pubKey, lastUsedLnurlPay);
+    }
+  }
+
+  Future<SignMessageResponse?> _generateSignature({
+    required String webhookUrl,
+    required int currentTime,
+    String? lnAddressUsername,
+  }) async {
+    final String username = lnAddressUsername?.isNotEmpty == true ? '-$lnAddressUsername' : '';
+    final String message = '$currentTime-$webhookUrl$username';
+
+    final SignMessageRequest req = SignMessageRequest(message: message);
+    return _breezSdkLiquid.instance?.signMessage(req: req);
+  }
+
+  Future<Map<String, String>> _postWebhookRegistrationRequest({
+    required String pubKey,
+    required String webhookUrl,
+    required int currentTime,
+    required String signature,
+    String? lnAddressUsername,
+  }) async {
+    final String lnurlWebhookUrl = '$lnurlServiceURL/lnurlpay/$pubKey';
+    final Uri uri = Uri.parse(lnurlWebhookUrl);
+
+    final http.Response jsonResponse = await http.post(
+      uri,
+      body: jsonEncode(
+        AddWebhookRequest(
+          time: currentTime,
+          webhookUrl: webhookUrl,
+          username: lnAddressUsername,
+          signature: signature,
+        ).toJson(),
+      ),
+    );
+
+    if (jsonResponse.statusCode == 200) {
+      final Map<String, dynamic> data = jsonDecode(jsonResponse.body);
+      final String lnurl = data['lnurl'];
+      final String lnAddress = data.containsKey('lightning_address') ? data['lightning_address'] : '';
+      _logger.info('Registered LnUrl Webhook: $webhookUrl, lnurl = $lnurl, lnAddress = $lnAddress');
+      return <String, String>{
+        'lnurl': lnurl,
+        'lnAddress': lnAddress,
+      };
+    } else {
+      // TODO(erdemyerebasmaz): Handle username conflicts(only when user has created a new wallet)
+      // Add a random four-digit identifier, a discriminator, as a suffix if user's username is taken(~1/600 probability of conflict)
+      // Add a retry & randomizer logic until first registration succeeds
+      // TODO(erdemyerebasmaz): Handle custom username conflicts
+      throw Exception('Failed to register LnUrl Webhook: ${jsonResponse.body}');
+    }
+  }
+
+  Future<Map<String, String>> updateLnAddressUsername(WalletInfo walletInfo, String username) async {
+    final String? webhookUrl = await getLnUrlPayKey();
+    if (webhookUrl == null) {
+      throw Exception('Failed to retrieve registered webhook.');
+    }
+    return await registerLnurlpay(walletInfo, webhookUrl, username: username);
+  }
+
+  Future<void> _invalidateLnurlPay(String pubKey, String toInvalidate) async {
+    final String lnurlWebhookUrl = '$lnurlServiceURL/lnurlpay/$pubKey';
+    final int currentTime = DateTime.now().millisecondsSinceEpoch ~/ 1000;
+    final SignMessageRequest req = SignMessageRequest(message: '$currentTime-$toInvalidate');
+    final SignMessageResponse? signMessageRes = _breezSdkLiquid.instance?.signMessage(req: req);
+    if (signMessageRes == null) {
+      throw Exception('Missing signature');
+    }
+    final Uri uri = Uri.parse(lnurlWebhookUrl);
+    final http.Response response = await http.delete(
+      uri,
+      body: jsonEncode(
+        RemoveWebhookRequest(
+          time: currentTime,
+          webhookUrl: toInvalidate,
+          signature: signMessageRes.signature,
+        ).toJson(),
+      ),
+    );
+    _logger.info('invalidate lnurl pay response: ${response.statusCode}');
+    await resetLnUrlPayKey();
+    await resetLnAddressUsername();
+  }
+
+  Future<void> setLnUrlPayKey({required String webhookUrl}) async {
+    return await _breezPreferences.setLnUrlPayKey(webhookUrl);
+  }
+
+  Future<String?> getLnUrlPayKey() async {
+    return await _breezPreferences.getLnUrlPayKey();
+  }
+
+  Future<void> resetLnUrlPayKey() async {
+    return await _breezPreferences.resetLnUrlPayKey();
+  }
+
+  Future<void> setLnAddressUsername({required String lnAddressUsername}) async {
+    return await _breezPreferences.setLnAddressUsername(lnAddressUsername);
+  }
+
+  Future<String?> getLnAddressUsername() async {
+    return await _breezPreferences.getLnAddressUsername();
+  }
+
+  Future<void> resetLnAddressUsername() async {
+    return await _breezPreferences.resetLnAddressUsername();
+  }
+}