feat(ads): implement demo ad provider for simulated ad loading

- Create

Author: fulleni

lib/ads/demo_ad_provider.dart

@@ -0,0 +1,88 @@
+import 'dart:async';
+
+import 'package:core/core.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/ads/ad_provider.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/ads/models/ad_theme_style.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/ads/models/banner_ad.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/ads/models/interstitial_ad.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/ads/models/native_ad.dart';
+import 'package:logging/logging.dart';
+import 'package:uuid/uuid.dart';
+
+/// {@template demo_ad_provider}
+/// A concrete implementation of [AdProvider] for the 'demo' ad platform.
+///
+/// This provider simulates ad loading for the demo environment without
+/// making actual ad network calls. It returns placeholder ad objects
+/// for native, banner, and interstitial ads.
+/// {@endtemplate}
+class DemoAdProvider implements AdProvider {
+  /// {@macro demo_ad_provider}
+  DemoAdProvider({Logger? logger})
+      : _logger = logger ?? Logger('DemoAdProvider');
+
+  final Logger _logger;
+  final Uuid _uuid = const Uuid();
+
+  @override
+  Future<void> initialize() async {
+    _logger.info('Demo Ad Provider initialized (no actual SDK to init).');
+    return Future.value();
+  }
+
+  @override
+  Future<NativeAd?> loadNativeAd({
+    required AdPlatformIdentifiers adPlatformIdentifiers,
+    required String? adId,
+    required AdThemeStyle adThemeStyle,
+    HeadlineImageStyle? headlineImageStyle,
+  }) async {
+    _logger.info('Simulating native ad load for demo environment.');
+    // Simulate a delay for loading.
+    await Future<void>.delayed(const Duration(milliseconds: 300));
+
+    return NativeAd(
+      id: _uuid.v4(),
+      provider: AdPlatformType.demo,
+      adObject: Object(), // Placeholder object
+      templateType: headlineImageStyle == HeadlineImageStyle.largeThumbnail
+          ? NativeAdTemplateType.medium
+          : NativeAdTemplateType.small,
+    );
+  }
+
+  @override
+  Future<BannerAd?> loadBannerAd({
+    required AdPlatformIdentifiers adPlatformIdentifiers,
+    required String? adId,
+    required AdThemeStyle adThemeStyle,
+    HeadlineImageStyle? headlineImageStyle,
+  }) async {
+    _logger.info('Simulating banner ad load for demo environment.');
+    // Simulate a delay for loading.
+    await Future<void>.delayed(const Duration(milliseconds: 300));
+
+    return BannerAd(
+      id: _uuid.v4(),
+      provider: AdPlatformType.demo,
+      adObject: Object(), // Placeholder object
+    );
+  }
+
+  @override
+  Future<InterstitialAd?> loadInterstitialAd({
+    required AdPlatformIdentifiers adPlatformIdentifiers,
+    required String? adId,
+    required AdThemeStyle adThemeStyle,
+  }) async {
+    _logger.info('Simulating interstitial ad load for demo environment.');
+    // Simulate a delay for loading.
+    await Future<void>.delayed(const Duration(milliseconds: 300));
+
+    return InterstitialAd(
+      id: _uuid.v4(),
+      provider: AdPlatformType.demo,
+      adObject: Object(), // Placeholder object
+    );
+  }
+}