import 'dart:async';
import 'dart:io';

import 'package:dio/dio.dart';
import 'package:http/http.dart' as http;
import 'package:nextcloud/nextcloud.dart';

import '../../session/session.dart';
import '../api_error.dart';
import '../http_errors.dart';
import '../marianumcloud/talk/talk_error.dart';
import 'app_exception.dart';
import 'network_exception.dart';
import 'parse_exception.dart';
import 'server_exception.dart';
import 'talk_exception.dart';

const String _defaultFallback =
    'Etwas ist schiefgelaufen. Bitte versuche es erneut.';
const String _tlsErrorMessage =
    'Die sichere Verbindung zum Server wurde abgelehnt (Zertifikat oder TLS-Fehler). '
    'Häufige Ursachen: falsche Geräte-Uhrzeit oder ein WLAN mit Anmeldeseite (z.B. Café/Hotel).';

AppException? _dioToAppException(DioException error) {
  switch (error.type) {
    case DioExceptionType.connectionTimeout:
    case DioExceptionType.sendTimeout:
    case DioExceptionType.receiveTimeout:
    case DioExceptionType.transformTimeout:
      return NetworkException.timeout(technicalDetails: error.message);
    case DioExceptionType.connectionError:
      return NetworkException(technicalDetails: error.message);
    case DioExceptionType.badCertificate:
      return const NetworkException(userMessage: _tlsErrorMessage);
    case DioExceptionType.badResponse:
      final status = error.response?.statusCode;
      return ServerException(
        statusCode: status ?? -1,
        technicalDetails: 'HTTP $status: ${error.message}',
      );
    case DioExceptionType.cancel:
    case DioExceptionType.unknown:
      final inner = error.error;
      if (inner is SocketException) {
        return NetworkException(technicalDetails: inner.message);
      }
      if (inner is HandshakeException) {
        return const NetworkException(userMessage: _tlsErrorMessage);
      }
      if (inner is FormatException) {
        return ParseException(technicalDetails: inner.message);
      }
      return null;
  }
}

final RegExp _davException = RegExp(
  r'<s:exception>\s*([^<]*?)\s*</s:exception>',
);
final RegExp _davMessage = RegExp(r'<s:message>\s*([^<]*?)\s*</s:message>');

/// The Sabre DAV error body of a failed WebDAV request: the exception class
/// (without its `Sabre\DAV\Exception\` namespace) and the server's message.
/// The class says what actually went wrong where the status is ambiguous —
/// MKCOL on an existing folder is a plain 405.
({String exception, String message})? parseDavError(String body) {
  final exception = _davException.firstMatch(body)?.group(1);
  if (exception == null || exception.isEmpty) return null;
  return (
    exception: exception.split('\\').last,
    message: _davMessage.firstMatch(body)?.group(1) ?? '',
  );
}

AppException? _davToAppException(
  int status,
  ({String exception, String message}) dav,
  String detail,
) {
  final userMessage = switch (dav.exception) {
    'MethodNotAllowed' when status == 405 =>
      'Ein Ordner oder eine Datei mit diesem Namen existiert bereits.',
    'PreconditionFailed' =>
      'Am Zielort existiert bereits ein Eintrag mit diesem Namen.',
    'Conflict' => 'Der übergeordnete Ordner existiert nicht mehr.',
    'Locked' =>
      'Der Eintrag wird gerade bearbeitet. Bitte versuche es gleich erneut.',
    'InsufficientStorage' =>
      'Der verfügbare Speicherplatz reicht dafür nicht aus.',
    _ => null,
  };
  if (userMessage == null) return null;
  return ServerException(
    statusCode: status,
    userMessage: userMessage,
    technicalDetails: detail,
    allowRetry: dav.exception == 'Locked',
  );
}

/// The nextcloud/dynamite clients throw [DynamiteApiException] on non-2xx.
/// Its toString() dumps every response header, so the details keep only the
/// status plus a trimmed body preview (same format as the Talk API errors).
AppException _dynamiteToAppException(DynamiteApiException error) {
  final status = error.statusCode;
  final dav = parseDavError(error.body);
  if (dav != null) {
    final detail = 'HTTP $status ${dav.exception}: ${dav.message}';
    return _davToAppException(status, dav, detail) ??
        exceptionForStatus(status, detail);
  }
  final preview = previewBody(error.body);
  final detail = preview.isEmpty
      ? 'HTTP $status'
      : 'HTTP $status body=$preview';
  if (status == 429) {
    return ServerException(
      statusCode: status,
      userMessage:
          'Zu viele Anfragen. Bitte warte einen Moment, bevor du es erneut versuchst.',
      technicalDetails: detail,
    );
  }
  return exceptionForStatus(status, detail);
}

String errorToUserMessage(Object? error, {String fallback = _defaultFallback}) {
  if (error == null) return fallback;
  if (error is AppException) return error.userMessage;

  if (error is TalkError) return TalkException(error).userMessage;
  if (error is NextcloudUnavailableException) {
    return 'Diese Funktion ist mit deinem Konto nicht verfügbar.';
  }

  if (error is DioException) {
    final mapped = _dioToAppException(error);
    if (mapped != null) return mapped.userMessage;
  }

  if (error is DynamiteApiException) {
    return _dynamiteToAppException(error).userMessage;
  }

  if (error is SocketException) {
    return const NetworkException().userMessage;
  }
  if (error is TimeoutException) {
    return NetworkException.timeout().userMessage;
  }
  if (error is http.ClientException) {
    return const NetworkException().userMessage;
  }
  if (error is HandshakeException) {
    return _tlsErrorMessage;
  }
  if (error is FormatException) {
    return const ParseException().userMessage;
  }
  if (error is ApiError) {
    return _stripDioPrefix(error.message);
  }

  return fallback;
}

String? errorToTechnicalDetails(Object? error) {
  if (error == null) return null;
  if (error is AppException) return error.technicalDetails ?? error.toString();
  if (error is TalkError) return TalkException(error).technicalDetails;
  if (error is DioException) {
    final mapped = _dioToAppException(error);
    if (mapped != null) return mapped.technicalDetails ?? mapped.toString();
  }
  if (error is DynamiteApiException) {
    final mapped = _dynamiteToAppException(error);
    return mapped.technicalDetails ?? mapped.toString();
  }
  return error.toString();
}

bool errorAllowsRetry(Object? error) {
  if (error == null) return true;
  if (error is AppException) return error.allowRetry;
  if (error is NextcloudUnavailableException) return false;
  if (error is DioException) {
    final mapped = _dioToAppException(error);
    if (mapped != null) return mapped.allowRetry;
  }
  if (error is DynamiteApiException) {
    return _dynamiteToAppException(error).allowRetry;
  }
  return true;
}

String _stripDioPrefix(String raw) {
  // ApiError messages embed full request URIs; only surface the first line.
  final firstLine = raw.split('\n').first.trim();
  return firstLine.isEmpty ? _defaultFallback : firstLine;
}