Obtainium/lib/services/source_service.dart

// Exposes functions related to interacting with App sources and retrieving App info
// Stateless - not a provider

import 'dart:convert';
import 'package:http/http.dart';

// Sub-classes used in App Source

class AppNames {
  late String author;
  late String name;

  AppNames(this.author, this.name);
}

class APKDetails {
  late String version;
  late String downloadUrl;

  APKDetails(this.version, this.downloadUrl);
}

// App Source abstract class (diff. implementations for GitHub, GitLab, etc.)

abstract class AppSource {
  String standardizeURL(String url);
  Future<APKDetails> getLatestAPKUrl(String standardUrl);
  AppNames getAppNames(String standardUrl);
}

// App class

class App {
  late String id;
  late String url;
  String? installedVersion;
  late String latestVersion;
  late String apkUrl;
  App(this.id, this.url, this.installedVersion, this.latestVersion,
      this.apkUrl);

  @override
  String toString() {
    return 'ID: $id URL: $url INSTALLED: $installedVersion LATEST: $latestVersion APK: $apkUrl';
  }
}

// Specific App Source classes

class GitHub implements AppSource {
  @override
  String standardizeURL(String url) {
    RegExp standardUrlRegEx = RegExp(r'^https?://github.com/[^/]*/[^/]*');
    var match = standardUrlRegEx.firstMatch(url.toLowerCase());
    if (match == null) {
      throw 'Not a valid URL';
    }
    return url.substring(0, match.end);
  }

  String convertURL(String url, String replaceText) {
    int tempInd1 = url.indexOf('://') + 3;
    int tempInd2 = url.substring(tempInd1).indexOf('/') + tempInd1;
    return '${url.substring(0, tempInd1)}$replaceText${url.substring(tempInd2)}';
  }

  @override
  Future<APKDetails> getLatestAPKUrl(String standardUrl) async {
    Response res = await get(Uri.parse(
        '${convertURL(standardUrl, 'api.github.com/repos')}/releases/latest'));
    if (res.statusCode == 200) {
      var release = jsonDecode(res.body);
      for (var i = 0; i < release['assets'].length; i++) {
        if (release['assets'][i]['name']
            .toString()
            .toLowerCase()
            .endsWith('.apk')) {
          return APKDetails(release['tag_name'],
              release['assets'][i]['browser_download_url']);
        }
      }
      throw 'No APK found';
    } else {
      throw 'Unable to fetch release info';
    }
  }

  @override
  AppNames getAppNames(String standardUrl) {
    String temp = standardUrl.substring(standardUrl.indexOf('://') + 3);
    List<String> names = temp.substring(temp.indexOf('/') + 1).split('/');
    return AppNames(names[0], names[1]);
  }
}

class SourceService {
  // Add more source classes here so they are available via the service
  var github = GitHub();
  AppSource getSource(String url) {
    if (url.toLowerCase().contains('://github.com')) {
      return github;
    }
    throw 'URL does not match a known source';
  }

  Future<App> getApp(String url) async {
    AppSource source = getSource(url);
    String standardUrl = source.standardizeURL(url);
    AppNames names = source.getAppNames(standardUrl);
    APKDetails apk = await source.getLatestAPKUrl(standardUrl);
    return App('${names.author}_${names.name}', standardUrl, null, apk.version,
        apk.downloadUrl);
  }
}