chore(cli): Add connection monitor

apps/cli/lib/src/cli/cli.dart

@@ -89,6 +89,8 @@ final class Cli {
         ? const SentryPerformance()
         : const CelestPerformance();
     ctx.storage = storage ?? Storage();
+    ctx.connectionMonitor.init();
+    await ctx.connectionMonitor.stream.first;
 
     try {
       _logger.finest('Initializing secure storage');
@@ -401,6 +403,7 @@ final class Cli {
     await _logFile?.close();
     await ctx.performance.close();
     ctx.httpClient.close();
+    ctx.connectionMonitor.close();
     exit(exitCode);
   }
 }

apps/cli/lib/src/context.dart

@@ -16,6 +16,7 @@ import 'package:celest_cli/src/project/project_paths.dart';
 import 'package:celest_cli/src/serialization/json_generator.dart';
 import 'package:celest_cli/src/storage/storage.dart';
 import 'package:celest_cli/src/types/type_helper.dart';
+import 'package:celest_cli/src/utils/connection_monitor.dart';
 import 'package:celest_cli/src/version.dart';
 import 'package:celest_cloud/celest_cloud.dart';
 import 'package:file/file.dart';
@@ -223,3 +224,5 @@ NativeSecureStorage secureStorage = storage.secure;
 
 /// The isolated [secureStorage] interface.
 IsolatedNativeStorage get isolatedSecureStorage => secureStorage.isolated;
+
+ConnectionMonitor connectionMonitor = ConnectionMonitor();

apps/cli/lib/src/pub/pub_action.dart

@@ -54,7 +54,13 @@ Future<void> runPub({
       ? Sdk.current.dart
       : (await celestProject.determineProjectType()).executable;
 
-  final command = <String>[exe, 'pub', action.name, if (verbose) '--verbose'];
+  final command = <String>[
+    exe,
+    'pub',
+    action.name,
+    if (verbose) '--verbose',
+    if (!connectionMonitor.isConnected) '--offline',
+  ];
   final logger = Logger(command.join(' '));
   logger.fine('Running `${command.join(' ')}` in "$workingDirectory"...');
   final process = await processManager.start(

apps/cli/lib/src/utils/connection_monitor.dart

@@ -0,0 +1,50 @@
+import 'dart:async';
+
+import 'package:celest_cli/src/context.dart';
+
+/// Monitors the local connection to the Internet.
+final class ConnectionMonitor {
+  /// We use pub.dev to check if an Internet connection is available generally
+  /// since this is mostly used to determine if we need to pass `--offline`
+  /// to pub commands.
+  static final Uri _checkUri = Uri.parse('https://pub.dev/');
+
+  final _connectionStream = StreamController<bool>.broadcast();
+
+  bool _isConnected = true;
+  bool get isConnected => _isConnected;
+  Stream<bool> get stream => _connectionStream.stream;
+
+  void init() {
+    _checkConnection();
+    Timer.periodic(const Duration(seconds: 5), (timer) {
+      if (_connectionStream.isClosed) {
+        timer.cancel();
+        return;
+      }
+      _checkConnection();
+    });
+  }
+
+  Future<void> _checkConnection() async {
+    final status = await checkConnection();
+    _isConnected = status;
+    if (!_connectionStream.isClosed) {
+      _connectionStream.add(status);
+    }
+  }
+
+  Future<bool> checkConnection() async {
+    try {
+      final result =
+          await httpClient.head(_checkUri).timeout(const Duration(seconds: 1));
+      return result.statusCode == 200;
+    } on Object {
+      return false;
+    }
+  }
+
+  void close() {
+    _connectionStream.close();
+  }
+}