Ported resolve_url from https://codeberg.org/outbag/app/src/branch/develop/deps/outbag-core/src/resolve_url.js

lib/backend/resolve_url.dart

@@ -0,0 +1,81 @@
+import 'package:localstore/localstore.dart';
+import 'package:http/http.dart' as http;
+import 'dart:convert';
+
+const String wellKnownPath = "/.well-known/outbag/server";
+const int defaultPort = 7223;
+
+Future<Uri> fetchWellKnown(String host, int port) async {
+  Uri uri = Uri(path: wellKnownPath, host: host, port: port, scheme: "https");
+  final resp = await http.get(uri);
+  final json = jsonDecode(resp.body);
+
+  return Uri(host: host, path: json['path'], port: json['port']);
+}
+
+class OutbagServer {
+  final String host;
+  final int port;
+  final String path;
+
+  final String tag;
+
+  const OutbagServer(
+    {required this.host,
+      required this.port,
+      required this.path,
+      required this.tag});
+
+  String get base {
+    return Uri(
+      host: host,
+      port: port,
+      path: path,
+      scheme: 'https',
+    ).toString();
+  }
+
+  void toDisk() async {
+    final db = Localstore.instance;
+    await db
+    .collection('meta')
+    .doc('server')
+    .set({'host': host, 'port': port, 'path': path, 'tag': tag});
+  }
+
+  static Future<OutbagServer> fromDisk() async {
+    final db = Localstore.instance;
+    final data = await db.collection('meta').doc('server').get();
+
+    return OutbagServer(
+      tag: data?['tag'],
+      host: data?['host'],
+      path: data?['path'],
+      port: data?['port']);
+  }
+}
+
+Future<OutbagServer> getOutbagServerUrl(String tag) async {
+  final rootUri = Uri.parse(tag.startsWith('https://') ? tag : 'https://$tag');
+
+  bool onRoot = rootUri.port == 443;
+
+  try {
+    final uri = await fetchWellKnown(rootUri.host, rootUri.port);
+    return OutbagServer(
+      host: rootUri.host,
+      port: uri.port,
+      path: uri.path,
+      tag: onRoot ? rootUri.host : '$rootUri.host:$uri.port');
+  } catch (_) {
+    if (onRoot) {
+      final uri = await fetchWellKnown(rootUri.host, defaultPort);
+      return OutbagServer(
+        host: rootUri.host,
+        port: uri.port,
+        path: uri.path,
+        tag: onRoot ? rootUri.host : '$rootUri.host:$uri.port');
+    }
+  }
+  throw Error();
+}