import 'dart:io';

import 'package:dio/dio.dart';
import 'package:flutter/services.dart';
import 'package:http/http.dart' as http;
import 'package:open_filex/open_filex.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:path_provider/path_provider.dart';

import 'android_download_helper.dart';
import 'download_result.dart';

final Dio _dio = Dio();

Future<bool> ensureStorageAccessImpl() async {
  if (Platform.isAndroid) {
    await Permission.notification.request();

    final sdkInt = await androidSdkInt();
    if (sdkInt != null && sdkInt < 29) {
      final storage = await Permission.storage.request();
      return storage.isGranted;
    }
    return true;
  }
  return true;
}

Future<DownloadResult> downloadEcardImpl({
  required String url,
  required String fileName,
  Map<String, String>? headers,
}) async {
  if (Platform.isIOS) {
    return _downloadOnIos(
      url: url,
      fileName: fileName,
      headers: headers,
    );
  }

  try {
    final hasPermission = await ensureStorageAccessImpl();
    if (!hasPermission) {
      return DownloadResult.failure(
        'Storage permission required',
      );
    }

    final safeFileName = _sanitizeFileName(fileName);
    final tempDir = await getTemporaryDirectory();
    final tempPath = '${tempDir.path}/$safeFileName';
    final tempFile = File(tempPath);
    if (await tempFile.exists()) {
      await tempFile.delete();
    }

    await _dio.download(
      url,
      tempPath,
      options: Options(
        headers: headers,
        responseType: ResponseType.bytes,
      ),
      deleteOnError: true,
    );

    if (!await tempFile.exists()) {
      return DownloadResult.failure('Download failed');
    }
    final bytes = await tempFile.readAsBytes();
    if (bytes.isEmpty) {
      await tempFile.delete();
      return DownloadResult.failure('Download failed');
    }

    final savedPath = await savePdfToAndroidDownloads(
      fileName: safeFileName,
      bytes: bytes,
    );
    await tempFile.delete();

    return DownloadResult.success(
      savedPath: savedPath,
      message: 'File saved under Download/$safeFileName',
    );
  } on FileSystemException {
    return DownloadResult.failure('Storage permission issue');
  } on DioException catch (e) {
    final hasStatusCode = e.response?.statusCode != null;
    final message = hasStatusCode
        ? 'Download failed (${e.response!.statusCode})'
        : 'Download failed';
    return DownloadResult.failure(message);
  } on PlatformException catch (e) {
    return DownloadResult.failure(e.message ?? 'Download failed');
  } catch (_) {
    return DownloadResult.failure('Download failed');
  }
}

Future<DownloadResult> _downloadOnIos({
  required String url,
  required String fileName,
  Map<String, String>? headers,
}) async {
  try {
    final safeFileName = _sanitizeFileName(fileName);
    final documentsDir = await getApplicationDocumentsDirectory();
    final downloadDir = Directory('${documentsDir.path}/ecards');
    if (!await downloadDir.exists()) {
      await downloadDir.create(recursive: true);
    }

    final filePath = '${downloadDir.path}/$safeFileName';
    final file = File(filePath);
    if (await file.exists()) {
      await file.delete();
    }

    final response = await http.get(Uri.parse(url), headers: headers);
    if (response.statusCode != 200) {
      return DownloadResult.failure(
        'Download failed (${response.statusCode})',
      );
    }

    await file.writeAsBytes(response.bodyBytes, flush: true);
    if (!await file.exists() || await file.length() == 0) {
      return DownloadResult.failure('Download failed');
    }

    try {
      await OpenFilex.open(filePath);
    } catch (_) {
      // File is saved even if the preview cannot be opened.
    }

    return DownloadResult.success(
      savedPath: filePath,
      message: 'E-Card downloaded',
    );
  } catch (_) {
    return DownloadResult.failure('Download failed');
  }
}

String _sanitizeFileName(String fileName) {
  final replaced = fileName.replaceAll(RegExp(r'[\\/:*?"<>|]'), '_').trim();
  if (replaced.isEmpty) return 'ecard.pdf';
  return replaced.toLowerCase().endsWith('.pdf') ? replaced : '$replaced.pdf';
}