/// Small helper that makes reading .Net json payloads defensive.
///
/// The backend is still in development, so property names might arrive in
/// PascalCase or camelCase and single properties might be missing. These
/// helpers keep the dto factories short and readable.
class JsonReader {
  const JsonReader._();

  /// Looks a key up, ignoring casing differences between .Net and Dart.
  static dynamic value(Map<String, dynamic> json, String key) {
    if (json.containsKey(key)) {
      return json[key];
    }

    final lowerKey = key.toLowerCase();
    for (final entry in json.entries) {
      if (entry.key.toLowerCase() == lowerKey) {
        return entry.value;
      }
    }
    return null;
  }

  static String requireString(Map<String, dynamic> json, String key) {
    final raw = value(json, key);
    if (raw == null) {
      throw FormatException('Missing required property "$key".');
    }
    return raw.toString();
  }

  static String? optionalString(Map<String, dynamic> json, String key) {
    final raw = value(json, key);
    return raw?.toString();
  }

  static DateTime requireDateTime(Map<String, dynamic> json, String key) {
    final parsed = optionalDateTime(json, key);
    if (parsed == null) {
      throw FormatException('Missing or invalid date property "$key".');
    }
    return parsed;
  }

  static DateTime? optionalDateTime(Map<String, dynamic> json, String key) {
    final raw = value(json, key);
    if (raw == null) {
      return null;
    }
    if (raw is DateTime) {
      return raw;
    }
    return DateTime.tryParse(raw.toString());
  }

  static bool? optionalBool(Map<String, dynamic> json, String key) {
    final raw = value(json, key);
    if (raw == null) {
      return null;
    }
    if (raw is bool) {
      return raw;
    }
    final text = raw.toString().toLowerCase();
    if (text == 'true' || text == '1') {
      return true;
    }
    if (text == 'false' || text == '0') {
      return false;
    }
    return null;
  }

  static int? optionalInt(Map<String, dynamic> json, String key) {
    final raw = value(json, key);
    if (raw == null) {
      return null;
    }
    if (raw is int) {
      return raw;
    }
    if (raw is num) {
      return raw.toInt();
    }
    return int.tryParse(raw.toString());
  }

  /// Maps a json array onto a list of models, tolerating a missing property.
  static List<T> list<T>(
    Map<String, dynamic> json,
    String key,
    T Function(Map<String, dynamic> json) fromJson,
  ) {
    final raw = value(json, key);
    if (raw is! List) {
      return <T>[];
    }
    return raw
        .whereType<Map>()
        .map((entry) => fromJson(Map<String, dynamic>.from(entry)))
        .toList(growable: false);
  }

  /// Resolves a .Net enum that can arrive either as its name or as its index.
  static T enumValue<T>(
    Map<String, dynamic> json,
    String key,
    List<T> values,
    String Function(T value) nameOf,
    T fallback,
  ) {
    final raw = value(json, key);
    if (raw == null) {
      return fallback;
    }

    if (raw is num) {
      final index = raw.toInt();
      if (index >= 0 && index < values.length) {
        return values[index];
      }
      return fallback;
    }

    final text = raw.toString().trim().toLowerCase();
    final normalized = _normalizeEnumName(text);
    for (final candidate in values) {
      if (_normalizeEnumName(nameOf(candidate).toLowerCase()) == normalized) {
        return candidate;
      }
    }

    final index = int.tryParse(text);
    if (index != null && index >= 0 && index < values.length) {
      return values[index];
    }
    return fallback;
  }

  /// Removes separators so that `AC_API` also matches `acApi`.
  static String _normalizeEnumName(String value) {
    return value.replaceAll(RegExp(r'[^a-z0-9]'), '');
  }
}