import 'dart:convert';

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/foundation.dart';
import 'package:http/http.dart' as http;
import '../auth/auth_service.dart';
import '../sync/r2_upload_service.dart';

abstract class CloudAccountCleanup {
  Future<void> deleteCloudData();
}

class AccountCloudCleanupService implements CloudAccountCleanup {
  final AuthService _auth;
  final FirebaseFirestore? _firestore;
  final http.Client _client;
  final String _workerUrl;

  AccountCloudCleanupService({
    required this._auth,
    FirebaseFirestore? firestore,
    http.Client? client,
    String? workerUrl,
  })  : _firestore = firestore ?? _resolveFirestore(),
        _client = client ?? http.Client(),
        _workerUrl = (workerUrl ?? R2UploadService.defaultWorkerUrl).replaceAll(RegExp(r'/+$'), '');

  static FirebaseFirestore? _resolveFirestore() {
    try {
      if (Firebase.apps.isNotEmpty) return FirebaseFirestore.instance;
    } catch (_) {}
    return null;
  }

  @override
  Future<void> deleteCloudData() async {
    final user = _auth.currentUser;
    if (user == null || user.isAnonymous) throw StateError('A permanent account is required.');
    final token = await _auth.getIdToken(true);
    if (token == null || token.isEmpty) throw StateError('A valid account session is required.');
    final endpoint = Uri.tryParse('$_workerUrl/account/cloud-data');
    if (endpoint == null || !endpoint.hasScheme ||
        (endpoint.scheme != 'http' && endpoint.scheme != 'https')) {
      throw StateError('MotorCloud cleanup endpoint is unavailable.');
    }

    final response = await _client.delete(
      endpoint,
      headers: {'Authorization': 'Bearer ${token.trim()}'},
    ).timeout(const Duration(seconds: 30));
    if (response.statusCode < 200 || response.statusCode >= 300) {
      final detail = _safeResponseDetail(response.body);
      debugPrint(
        '[DELETE_FLOW] cloud cleanup response status=${response.statusCode} '
        'body=$detail',
      );
      throw StateError(
        'MotorCloud cleanup was not completed (${response.statusCode}).',
      );
    }
    if (response.statusCode != 204 && !_isSuccessfulWorkerResponse(response.body)) {
      final detail = _safeResponseDetail(response.body);
      debugPrint('[DELETE_FLOW] cloud cleanup response malformed body=$detail');
      throw StateError('MotorCloud cleanup returned an invalid response.');
    }

    final firestore = _firestore;
    if (firestore == null) throw StateError('MotorCloud database is unavailable.');
    final userRef = firestore.collection('users').doc(user.uid);
    final rides = await userRef.collection('rides').get();
    for (final doc in rides.docs) {
      await _deleteCollection(doc.reference.collection('events'));
      await _deleteCollection(doc.reference.collection('performance'));
    }

    await _deleteCollection(userRef.collection('rides'));
    await _deleteCollection(userRef.collection('motorcycles'));
    await _deleteCollection(userRef.collection('trips'));
    await _deleteCollection(userRef.collection('events'));
    await _deleteCollection(userRef.collection('friends'));
    await _deleteCollection(userRef.collection('friend_requests_incoming'));
    await _deleteCollection(userRef.collection('friend_requests_outgoing'));
    await _deleteCollection(userRef.collection('blocks'));

    // Release handle reservation if exists
    final userSnap = await userRef.get();
    final handle = userSnap.data()?['username'] as String?;
    if (handle != null && handle.isNotEmpty) {
      await firestore.collection('handles').doc(handle.toLowerCase()).delete();
    }

    // Delete the profile last so retries can still discover the account scope.
    final profileBatch = firestore.batch()..delete(userRef);
    await profileBatch.commit();
  }

  Future<void> _deleteCollection(CollectionReference<Map<String, dynamic>> collection) async {
    final snapshot = await collection.get();
    for (var offset = 0; offset < snapshot.docs.length; offset += 450) {
      final batch = _firestore!.batch();
      final end = (offset + 450).clamp(0, snapshot.docs.length);
      for (final doc in snapshot.docs.sublist(offset, end)) {
        batch.delete(doc.reference);
      }
      await batch.commit();
    }
  }

  String _safeResponseDetail(String body) {
    final sanitized = body
        .replaceAll(RegExp(r'Bearer\s+\S+', caseSensitive: false), 'Bearer [REDACTED]')
        .replaceAll(RegExp(r'"(?:token|password|secret|pat)"\s*:\s*"[^"]*"', caseSensitive: false), '"credential":"[REDACTED]"');
    final compact = sanitized.replaceAll(RegExp(r'\s+'), ' ').trim();
    if (compact.isEmpty) return '[empty]';
    return compact.length > 240 ? compact.substring(0, 240) : compact;
  }

  bool _isSuccessfulWorkerResponse(String body) {
    try {
      final decoded = jsonDecode(body);
      return decoded is Map<String, dynamic> &&
          decoded['success'] == true &&
          decoded['deletedObjects'] is int &&
          (decoded['deletedObjects'] as int) >= 0;
    } on FormatException {
      return false;
    }
  }
}