import 'dart:convert';

import 'package:flutter_secure_storage/flutter_secure_storage.dart';

/// A guardian login request waiting for its code or link. Persisted because
/// Android often kills the app while the user reads the mail.
class PendingGuardianRequest {
  static const int defaultCodeLength = 6;

  final String requestId;
  final String email;
  final String deviceSecret;
  final DateTime expiresAt;
  final DateTime resendAvailableAt;
  final int codeLength;

  const PendingGuardianRequest({
    required this.requestId,
    required this.email,
    required this.deviceSecret,
    required this.expiresAt,
    required this.resendAvailableAt,
    this.codeLength = defaultCodeLength,
  });

  bool isExpired(DateTime now) => !now.isBefore(expiresAt);

  Map<String, Object> toJson() => {
    'requestId': requestId,
    'email': email,
    'deviceSecret': deviceSecret,
    'expiresAt': expiresAt.toIso8601String(),
    'resendAvailableAt': resendAvailableAt.toIso8601String(),
    'codeLength': codeLength,
  };

  static PendingGuardianRequest? fromJson(Map<String, dynamic> json) {
    try {
      return PendingGuardianRequest(
        requestId: json['requestId'] as String,
        email: json['email'] as String,
        deviceSecret: json['deviceSecret'] as String,
        expiresAt: DateTime.parse(json['expiresAt'] as String),
        resendAvailableAt: DateTime.parse(json['resendAvailableAt'] as String),
        codeLength: json['codeLength'] as int? ?? defaultCodeLength,
      );
    } on Object {
      return null;
    }
  }
}

class PendingGuardianRequestStore {
  static const _key = 'guardian_login_pending_request';
  static const FlutterSecureStorage _storage = FlutterSecureStorage(
    iOptions: IOSOptions(accessibility: KeychainAccessibility.first_unlock),
  );

  const PendingGuardianRequestStore();

  Future<PendingGuardianRequest?> read() async {
    try {
      final raw = await _storage.read(key: _key);
      if (raw == null) return null;
      return PendingGuardianRequest.fromJson(
        jsonDecode(raw) as Map<String, dynamic>,
      );
    } on Object {
      return null;
    }
  }

  Future<void> write(PendingGuardianRequest request) =>
      _storage.write(key: _key, value: jsonEncode(request.toJson()));

  Future<void> clear() async {
    try {
      await _storage.delete(key: _key);
    } on Object {
      // Nothing stored or keystore unavailable.
    }
  }
}