import 'dart:convert';

import 'package:firebase_remote_config/firebase_remote_config.dart';
import 'package:flutter/foundation.dart' show kDebugMode;
import 'package:flutter/services.dart' show rootBundle;
import 'package:hmg_patient_app_new/services/logger_service.dart';

/// Firebase Remote Config wrapper. Fully generic — the app never hardcodes
/// occasion-specific values here; it only knows about the `occasion_config`
/// remote key and reads whatever JSON is published on the Firebase console.
abstract class RemoteConfigService {
  /// Must be called once at startup, before the first frame if possible.
  Future<void> initialize();

  /// Fetches the latest values from Firebase (respecting the configured
  /// minimum fetch interval) and activates them.
  Future<bool> fetchAndActivate();

  /// Raw JSON array string currently held for the `occasion_config` key —
  /// a list of scheduled occasions (bundled default `[]` until the first
  /// successful fetch/activate).
  String get occasionConfigRawJson;
}

class RemoteConfigServiceImp implements RemoteConfigService {
  static const String occasionConfigKey = 'occasion_config';
  static const String _defaultConfigAssetPath = 'assets/json/default_occasion_config.json';

  final LoggerService loggerService;
  final FirebaseRemoteConfig _remoteConfig;

  RemoteConfigServiceImp({
    required this.loggerService,
    FirebaseRemoteConfig? remoteConfig,
  }) : _remoteConfig = remoteConfig ?? FirebaseRemoteConfig.instance;

  @override
  Future<void> initialize() async {
    try {
      await _remoteConfig.setConfigSettings(
        RemoteConfigSettings(
          fetchTimeout: const Duration(seconds: 10),
          // In debug builds, always fetch fresh values so you can test
          // Remote Config changes instantly without waiting/throttling.
          // Release/profile builds keep a 1-hour minimum interval —
          // balances timely occasion-theme rollout against not hammering
          // Remote Config across the whole user base.
          minimumFetchInterval: kDebugMode ? Duration.zero : const Duration(hours: 1),
        ),
      );

      // Bundled fallback so behaviour is deterministic (and identical to the
      // current app look) before the very first successful remote fetch.
      final defaultJson = await rootBundle.loadString(_defaultConfigAssetPath);
      await _remoteConfig.setDefaults(<String, dynamic>{occasionConfigKey: defaultJson});
    } catch (ex) {
      loggerService.logError('RemoteConfigService.initialize error: $ex');
    }
  }

  @override
  Future<bool> fetchAndActivate() async {
    try {
      return await _remoteConfig.fetchAndActivate();
    } catch (ex) {
      loggerService.logError('RemoteConfigService.fetchAndActivate error: $ex');
      return false;
    }
  }

  @override
  String get occasionConfigRawJson {
    try {
      final value = _remoteConfig.getString(occasionConfigKey);
      if (value.isEmpty) return _fallbackDisabledJson;
      // Validate JSON shape early; if malformed, fall back safely.
      json.decode(value);
      return value;
    } catch (ex) {
      loggerService.logError('RemoteConfigService.occasionConfigRawJson parse error: $ex');
      return _fallbackDisabledJson;
    }
  }

  /// Empty schedule — [OccasionConfigModel.resolveActive] treats this the
  /// same as "no occasion currently active".
  static const String _fallbackDisabledJson = '[]';
}