Feature/eager init #74

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		# Changelog

	## Upcoming Release
	- refactor!: shift to eager loading for a robust, fail-fast startup.

		## 1.0.1 - 2025年10月17日

		- chore: A new migration ensures that existing user preference documents are updated to include the savedFilters field, initialized as an empty array.
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7 changes: 7 additions & 0 deletions README.md

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		---

	### ✨ Eager Loading & Fail-Fast Startup
	- Robust Initialization: The server now initializes all critical dependencies (database connection, migrations, seeding) before it starts accepting any requests.
	- Fail-Fast by Design: If any part of the startup process fails (e.g., the database is down), the server will immediately exit with a clear error.
	> Your Advantage: This eliminates startup race conditions and ensures the server is either fully operational or not running at all. It provides a highly predictable and stable production environment, preventing the server from running in a broken state.

	---

		### 🔌 Robust Dependency Injection
		- Testable & Modular: A centralized dependency injection system makes the entire application highly modular and easy to test.
		- Swappable Implementations: Easily swap out core components—like the database (MongoDB), email provider (SendGrid), or storage services—without rewriting your business logic.
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92 changes: 92 additions & 0 deletions bin/main.dart

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	// ignore_for_file: avoid_print

	import 'dart:async';
	import 'dart:io';

	import 'package:dart_frog/dart_frog.dart';
	import 'package:flutter_news_app_api_server_full_source_code/src/config/app_dependencies.dart';
	import 'package:logging/logging.dart';

	// Import the generated server entrypoint to access `buildRootHandler`.
	import '../.dart_frog/server.dart' as dart_frog;

	/// The main entrypoint for the application.
	///
	/// This custom entrypoint implements an "eager loading" strategy. It ensures
	/// that all critical application dependencies are initialized before the
	/// HTTP server starts listening for requests.
	///
	/// If any part of the dependency initialization fails (e.g., database
	/// connection, migrations), the process will log a fatal error and exit,
	/// preventing the server from running in a broken state. This is a robust,
	/// "fail-fast" approach.
	Future<void> main(List<String> args) async {
	// Use a local logger for startup-specific messages.
	// This is also the ideal place to configure the root logger for the entire
	// application, as it's guaranteed to run only once at startup.
	Logger.root.level = Level.ALL;
	Logger.root.onRecord.listen((record) {
	final message = StringBuffer()
	..write('${record.level.name}: ${record.time}: ${record.loggerName}: ')
	..writeln(record.message);

	if (record.error != null) {
	message.writeln(' ERROR: ${record.error}');
	}
	if (record.stackTrace != null) {
	message.writeln(' STACK TRACE: ${record.stackTrace}');
	}
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	// Write the log message atomically to stdout.
	stdout.write(message.toString());
	});

	final log = Logger('EagerEntrypoint');
	HttpServer? server;

	Future<void> shutdown([String? signal]) async {
	log.info('Received ${signal ?? 'signal'}. Shutting down gracefully...');
	// Stop accepting new connections.
	await server?.close();
	// Dispose all application dependencies.
	await AppDependencies.instance.dispose();
	log.info('Shutdown complete.');
	exit(0);
	}

	// Listen for termination signals.
	ProcessSignal.sigint.watch().listen((_) => shutdown('SIGINT'));
	// SIGTERM is not supported on Windows. Attempting to listen to it will throw.
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	if (!Platform.isWindows) {
	ProcessSignal.sigterm.watch().listen((_) => shutdown('SIGTERM'));
	}

	try {
	log.info('EAGER_INIT: Initializing application dependencies...');

	// Eagerly initialize all dependencies. If this fails, it will throw.
	await AppDependencies.instance.init();

	log.info('EAGER_INIT: Dependencies initialized successfully.');
	log.info('EAGER_INIT: Starting Dart Frog server...');

	// Start the server directly without the hot reload wrapper.
	final address = InternetAddress.anyIPv6;
	final port = int.tryParse(Platform.environment['PORT'] ?? '8080') ?? 8080;

	// Explicitly cast the handler to resolve the type ambiguity.
	final handler = dart_frog.buildRootHandler() as Handler;
	server = await serve(handler, address, port);
	log.info(
	'Server listening on http://${server.address.host}:${server.port}',
	);
	} catch (e, s) {
	log.severe('EAGER_INIT: FATAL: Failed to start server.', e, s);
	// Log directly to stderr and flush to ensure the message is captured
	// before the process exits, which is crucial for debugging startup errors.
	stderr.writeln('EAGER_INIT: FATAL: Failed to start server. Error: $e\nStack Trace: $s');
	await stderr.flush();
	// Exit the process if initialization fails.
	exit(1);
	}
	}

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