import 'dart:io';

import 'package:crypto/crypto.dart';
import 'package:device_info_plus/device_info_plus.dart';
import 'package:flutter/services.dart';
import 'package:open_filex/open_filex.dart';
import 'package:package_info_plus/package_info_plus.dart';
import 'package:path_provider/path_provider.dart';

import 'update_checker.dart';

enum UpdateInstallStatus {
  done,
  noAsset,
  downloadFailed,
  integrityFailed,
  installFailed,
}

class UpdateInstallResult {
  final UpdateInstallStatus status;
  final String? error;

  const UpdateInstallResult(this.status, {this.error});

  bool get ok => status == UpdateInstallStatus.done;
}

abstract class UpdateInstaller {
  static const MethodChannel _integrityChannel = MethodChannel(
    'ru.qlyra.app/update_integrity',
  );

  static bool get isSupported => Platform.isAndroid;

  static Future<UpdateInstallResult> downloadAndInstall(
    AppUpdateInfo info, {
    void Function(double progress)? onProgress,
  }) async {
    final artifact = await resolveApkArtifact(info);
    if (artifact == null) {
      return const UpdateInstallResult(UpdateInstallStatus.noAsset);
    }

    File file;
    try {
      file = await _download(artifact, info.tag, onProgress);
    } on UpdateIntegrityException catch (e) {
      return UpdateInstallResult(
        UpdateInstallStatus.integrityFailed,
        error: e.message,
      );
    } catch (e) {
      return UpdateInstallResult(
        UpdateInstallStatus.downloadFailed,
        error: e.toString(),
      );
    }

    final signerMatches = await _verifySigner(file.path);
    if (!signerMatches) {
      await file.delete();
      return const UpdateInstallResult(
        UpdateInstallStatus.integrityFailed,
        error: 'APK signer does not match the installed application',
      );
    }

    final opened = await OpenFilex.open(
      file.path,
      type: 'application/vnd.android.package-archive',
    );
    if (opened.type != ResultType.done) {
      return UpdateInstallResult(
        UpdateInstallStatus.installFailed,
        error: opened.message,
      );
    }
    return const UpdateInstallResult(UpdateInstallStatus.done);
  }

  static Future<AppUpdateArtifact?> resolveApkArtifact(
    AppUpdateInfo info,
  ) async {
    if (!Platform.isAndroid || info.artifacts.isEmpty) return null;

    final packageInfo = await PackageInfo.fromPlatform();
    final androidInfo = await DeviceInfoPlugin().androidInfo;
    return selectArtifact(
      info.artifacts,
      packageInfo.packageName,
      androidInfo.supportedAbis,
    );
  }

  static AppUpdateArtifact? selectArtifact(
    List<AppUpdateArtifact> artifacts,
    String packageName,
    List<String> supportedAbis,
  ) {
    final flavor = UpdateChecker.manifestSlugForPackageName(packageName);
    final matching = artifacts.where((item) => item.flavor == flavor).toList();
    for (final abi in supportedAbis) {
      for (final artifact in matching) {
        if (artifact.abi == abi) return artifact;
      }
    }
    for (final artifact in matching) {
      if (artifact.abi == 'universal') return artifact;
    }
    return null;
  }

  static Future<File> _download(
    AppUpdateArtifact artifact,
    String tag,
    void Function(double progress)? onProgress,
  ) async {
    final dir = await getTemporaryDirectory();
    final safeTag = tag.replaceAll(RegExp(r'[^A-Za-z0-9._-]'), '_');
    final file = File('${dir.path}/qlyra-update-$safeTag.apk');
    final part = File('${file.path}.part');

    final client = HttpClient();
    try {
      final uri = Uri.parse(artifact.url);
      final request = await client.getUrl(uri);
      request.headers.set(HttpHeaders.userAgentHeader, 'QlyraUpdateInstaller');
      final response = await request.close();
      if (response.statusCode != HttpStatus.ok) {
        await response.drain<void>();
        throw HttpException('HTTP ${response.statusCode}', uri: uri);
      }

      final total = response.contentLength;
      if (total >= 0 && total != artifact.sizeBytes) {
        await response.drain<void>();
        throw UpdateIntegrityException('Unexpected Content-Length: $total');
      }
      var received = 0;
      final sink = part.openWrite();
      try {
        await for (final chunk in response) {
          received += chunk.length;
          if (received > artifact.sizeBytes) {
            throw const UpdateIntegrityException('APK is larger than expected');
          }
          sink.add(chunk);
          if (onProgress != null) {
            onProgress(received / artifact.sizeBytes);
          }
        }
      } finally {
        await sink.close();
      }
      if (received != artifact.sizeBytes) {
        throw UpdateIntegrityException('Unexpected APK size: $received bytes');
      }
      await verifyArtifact(part, artifact);
      if (await file.exists()) await file.delete();
      await part.rename(file.path);
      return file;
    } catch (e) {
      if (await part.exists()) {
        try {
          await part.delete();
        } catch (_) {}
      }
      rethrow;
    } finally {
      client.close();
    }
  }

  static Future<bool> _verifySigner(String path) async {
    try {
      return await _integrityChannel.invokeMethod<bool>('verifyApkSigner', {
            'path': path,
          }) ??
          false;
    } on PlatformException {
      return false;
    }
  }

  static Future<void> verifyArtifact(
    File file,
    AppUpdateArtifact artifact,
  ) async {
    final size = await file.length();
    if (size != artifact.sizeBytes) {
      throw UpdateIntegrityException('Unexpected APK size: $size bytes');
    }
    final digest = await sha256.bind(file.openRead()).first;
    if (digest.toString().toLowerCase() != artifact.sha256.toLowerCase()) {
      throw const UpdateIntegrityException('APK SHA-256 mismatch');
    }
  }
}

class UpdateIntegrityException implements Exception {
  final String message;

  const UpdateIntegrityException(this.message);

  @override
  String toString() => message;
}