feat: add Gemini and Spartan protocol support

app/test/spartan_test.dart

@@ -0,0 +1,129 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+
+import 'fake_protocol_server.dart';
+
+import 'package:mews/protocols/spartan.dart';
+
+Uri open(String path, FakeSpartanServer server) =>
+    Uri.parse('spartan://localhost:${server.port}$path');
+
+void main() {
+  late FakeSpartanServer server;
+  late StreamSubscription<Socket> answers;
+  final client = SpartanClient(timeout: const Duration(seconds: 5));
+
+  tearDown(() async {
+    await answers.cancel();
+    await server.close();
+  });
+
+  test('a success answers with status, meta and body', () async {
+    server = FakeSpartanServer();
+    await server.start();
+    var requested = '';
+    answers = server.answer((line, upload, socket) {
+      requested = line;
+      socket.add(utf8.encode('2 text/gemini\r\nhello'));
+    });
+
+    final response = await client.fetch(open('/page', server));
+
+    expect(response.status, 2);
+    expect(response.meta, 'text/gemini');
+    expect(utf8.decode(response.body!), 'hello');
+    expect(requested, 'localhost /page 0');
+  });
+
+  test('an upload rides behind the request line', () async {
+    server = FakeSpartanServer();
+    await server.start();
+    var requested = '';
+    var uploaded = '';
+    answers = server.answer((line, upload, socket) {
+      requested = line;
+      uploaded = utf8.decode(upload);
+      socket.add(utf8.encode('2 text/gemini\r\nok'));
+    });
+
+    final response =
+        await client.fetch(open('/echo', server), upload: utf8.encode('payload'));
+
+    expect(response.status, 2);
+    expect(requested, 'localhost /echo 7');
+    expect(uploaded, 'payload');
+  });
+
+  test('a query is part of the path', () async {
+    server = FakeSpartanServer();
+    await server.start();
+    var requested = '';
+    answers = server.answer((line, upload, socket) {
+      requested = line;
+      socket.add(utf8.encode('2 text/gemini\r\nok'));
+    });
+
+    await client.fetch(open('/search?q=phones', server));
+
+    expect(requested, 'localhost /search?q=phones 0');
+  });
+
+  test('a redirect is followed to the final address', () async {
+    server = FakeSpartanServer();
+    await server.start();
+    final requests = <String>[];
+    answers = server.answer((line, upload, socket) async {
+      requests.add(line);
+      if (line.contains('/here')) {
+        socket.add(utf8.encode('3 ${open('/there', server)}\r\n'));
+      } else {
+        socket.add(utf8.encode('2 text/gemini\r\narrived'));
+      }
+    });
+
+    final response = await client.fetch(open('/here', server));
+
+    expect(response.status, 2);
+    expect(utf8.decode(response.body!), 'arrived');
+    expect(response.url.path, '/there');
+    expect(requests, hasLength(2));
+  });
+
+  test('a redirect loop gives up after five hops', () async {
+    server = FakeSpartanServer();
+    await server.start();
+    final requests = <String>[];
+    answers = server.answer((line, upload, socket) async {
+      requests.add(line);
+      socket.add(utf8.encode('3 ${open('/loop', server)}\r\n'));
+    });
+
+    await expectLater(
+      client.fetch(open('/loop', server)),
+      throwsA(isA<SpartanTooManyRedirects>()),
+    );
+    expect(requests, hasLength(6));
+  });
+
+  test('an error status carries its message', () async {
+    server = FakeSpartanServer();
+    await server.start();
+    answers = server.answer((line, upload, socket) =>
+        socket.add(utf8.encode('4 Nothing lives here\r\n')));
+
+    final response = await client.fetch(open('/gone', server));
+
+    expect(response.status, 4);
+    expect(response.meta, 'Nothing lives here');
+    expect(response.body, isNull);
+  });
+
+  test('an unreachable host is one failure', () async {
+    final nowhere = Uri.parse('spartan://localhost:1/');
+
+    await expectLater(client.fetch(nowhere), throwsA(isA<SpartanException>()));
+  });
+}