Integrate logging system into Flutter app with service registration and testing setup

finlog_app/fluttery/lib/fluttery.dart

@@ -1,5 +1,61 @@
-/// A Calculator.
-class Calculator {
-  /// Returns [value] plus 1.
-  int addOne(int value) => value + 1;
+library;
+
+import 'package:fluttery/logger/logger.dart';
+import 'package:fluttery/src/logger/logger_impl.dart';
+import 'package:kiwi/kiwi.dart';
+
+/// A class to manage services.
+class App {
+  static final _AppService _appService = _AppService();
+
+  /// Registers a service with a factory function to instantiate the implementation.
+  ///
+  /// This ensures that the implementation is created when the service is requested.
+  ///
+  /// `implFactory` - A factory method to create the service implementation.
+  static void registerService<T extends Service>(T Function() implFactory) {
+    _appService.registerSingleton<T>(implFactory);
+  }
+
+  /// Retrieves the registered service.
+  ///
+  /// Returns an instance of the registered service.
+  static T service<T extends Service>() {
+    return _appService.resolve<T>();
+  }
+
+  /// Registers the default services required by the application.
+  static void registerDefaultServices() {
+    registerService<Logger>(() => LoggerImpl());
+  }
+}
+
+/// Abstract class to represent a service.
+abstract class Service {}
+
+/// Internal class to manage the registration and resolution of services.
+class _AppService {
+  static _AppService? _singleton;
+
+  static final KiwiContainer _kiwi = KiwiContainer();
+
+  /// Factory constructor to ensure singleton instance of _AppService.
+  factory _AppService() => _singleton ??= _AppService._();
+
+  /// Private constructor.
+  _AppService._();
+
+  /// Registers a singleton service with a factory function to create the instance.
+  ///
+  /// `serviceFactory` - A factory method to create the service implementation.
+  void registerSingleton<T extends Service>(T Function() serviceFactory) {
+    _kiwi.registerFactory<T>((c) => serviceFactory());
+  }
+
+  /// Resolves and retrieves the registered service.
+  ///
+  /// Returns an instance of the registered service.
+  T resolve<T extends Service>() {
+    return _kiwi.resolve<T>();
+  }
 }

finlog_app/fluttery/lib/logger/logger.dart

@@ -0,0 +1,33 @@
+import 'package:fluttery/fluttery.dart';
+import 'package:logging/logging.dart' as lib;
+
+/// Abstract class for logging service.
+/// Provides methods for different log levels and configuration.
+abstract class Logger extends Service {
+  /// Logs an informational message.
+  ///
+  /// [message] is the information to log.
+  void info(String message);
+
+  /// Logs a warning message.
+  ///
+  /// [message] is the warning to log.
+  void warning(String message);
+
+  /// Logs an error message with optional error and stack trace.
+  ///
+  /// [message] is the error message to log.
+  /// [error] is the optional error object associated with this log entry.
+  /// [stackTrace] is the optional stack trace associated with this log entry.
+  void error(String message, [Object? error, StackTrace? stackTrace]);
+
+  /// Logs a debug message.
+  ///
+  /// [message] is the debug message to log.
+  void debug(String message);
+
+  /// Sets the log level for the logger.
+  ///
+  /// [level] is the new log level to set.
+  void setLogLevel(lib.Level level);
+}

finlog_app/fluttery/lib/src/logger/logger_impl.dart

@@ -0,0 +1,57 @@
+import 'package:flutter/material.dart';
+import 'package:fluttery/logger/logger.dart';
+import 'package:logging/logging.dart' as lib;
+
+// ignore_for_file: avoid_print
+class LoggerImpl implements Logger {
+  final lib.Logger _logger;
+
+  // coverage:ignore-start
+  /// Constructor
+  LoggerImpl() : _logger = lib.Logger("Logger") {
+    _logger.onRecord.listen((lib.LogRecord record) {
+      print('${record.level.name}: ${record.time}: ${record.message}');
+      if (record.error != null) {
+        print('Error: ${record.error}');
+      }
+      if (record.stackTrace != null) {
+        print('Stack Trace: ${record.stackTrace}');
+      }
+    });
+  }
+
+  // coverage:ignore-end
+  @visibleForTesting
+  factory LoggerImpl.forTest(lib.Logger logger) {
+    final instance = LoggerImpl._internal(logger);
+    return instance;
+  }
+
+  // Private internal constructor
+  LoggerImpl._internal(this._logger);
+
+  @override
+  void info(String message) {
+    _logger.info(message);
+  }
+
+  @override
+  void warning(String message) {
+    _logger.warning(message);
+  }
+
+  @override
+  void error(String message, [Object? error, StackTrace? stackTrace]) {
+    _logger.severe(message, error, stackTrace);
+  }
+
+  @override
+  void debug(String message) {
+    _logger.fine(message);
+  }
+
+  @override
+  void setLogLevel(lib.Level level) {
+    _logger.level = level;
+  }
+}