feat: add Gemini and Spartan protocol support

app/test/gemini_test.dart

@@ -0,0 +1,163 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:crypto/crypto.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'fake_protocol_server.dart';
+
+import 'package:mews/protocols/gemini.dart';
+import 'package:mews/protocols/tofu.dart';
+
+String fixtureFingerprint(String certName) {
+  final pem = File('test/fixtures/$certName-cert.pem').readAsStringSync();
+  final body = pem
+      .replaceAll(RegExp(r'-----(BEGIN|END) CERTIFICATE-----'), '')
+      .replaceAll(RegExp(r'\s'), '');
+  return sha256.convert(base64.decode(body)).toString();
+}
+
+Future<Uri> open(String path, FakeGeminiServer server) =>
+    Future.value(Uri.parse('gemini://localhost:${server.port}$path'));
+
+void main() {
+  late FakeGeminiServer server;
+  late StreamSubscription<SecureSocket> answers;
+  final client = GeminiClient(timeout: const Duration(seconds: 5));
+
+  tearDown(() async {
+    await answers.cancel();
+    await server.close();
+  });
+
+  test('a success answers with status, meta and body', () async {
+    server = FakeGeminiServer('gemini-test-a');
+    await server.start();
+    var requested = '';
+    answers = server.answer((line, socket) async {
+      requested = line;
+      socket.add(utf8.encode('20 text/gemini\r\nhello'));
+    });
+
+    final response = await client.fetch(await open('/', server));
+
+    expect(response.status, 20);
+    expect(response.meta, 'text/gemini');
+    expect(utf8.decode(response.body!), 'hello');
+    expect(requested, 'gemini://localhost:${server.port}/');
+  });
+
+  test('the first visit pins the presented certificate', () async {
+    server = FakeGeminiServer('gemini-test-a');
+    await server.start();
+    answers = server.answer((line, socket) => socket.add(utf8.encode('20 text/gemini\r\n')));
+
+    final response = await client.fetch(await open('/', server));
+
+    expect(response.pinUpdates, hasLength(1));
+    final update = response.pinUpdates.single;
+    expect(update.host, 'localhost');
+    expect(update.port, server.port);
+    expect(update.pin.fingerprint, fixtureFingerprint('gemini-test-a'));
+  });
+
+  test('a matching pin is left alone', () async {
+    server = FakeGeminiServer('gemini-test-a');
+    await server.start();
+    answers = server.answer((line, socket) => socket.add(utf8.encode('20 text/gemini\r\n')));
+    final pins = {
+      'localhost:${server.port}':
+          TofuPin(fingerprint: fixtureFingerprint('gemini-test-a'), expires: DateTime(2100)),
+    };
+
+    final response = await client.fetch(await open('/', server), pins: pins);
+
+    expect(response.pinUpdates, isEmpty);
+  });
+
+  test('a changed certificate is refused while the pin is valid', () async {
+    server = FakeGeminiServer('gemini-test-b');
+    await server.start();
+    answers = server.answer((line, socket) => socket.add(utf8.encode('20 text/gemini\r\n')));
+    final pins = {
+      'localhost:${server.port}':
+          TofuPin(fingerprint: fixtureFingerprint('gemini-test-a'), expires: DateTime(2100)),
+    };
+
+    await expectLater(
+      client.fetch(await open('/', server), pins: pins),
+      throwsA(isA<GeminiCertificateChanged>()),
+    );
+  });
+
+  test('a changed certificate renews an expired pin', () async {
+    server = FakeGeminiServer('gemini-test-b');
+    await server.start();
+    answers = server.answer((line, socket) => socket.add(utf8.encode('20 text/gemini\r\n')));
+    final pins = {
+      'localhost:${server.port}':
+          TofuPin(fingerprint: fixtureFingerprint('gemini-test-a'), expires: DateTime(2020)),
+    };
+
+    final response = await client.fetch(await open('/', server), pins: pins);
+
+    expect(response.pinUpdates.single.pin.fingerprint, fixtureFingerprint('gemini-test-b'));
+  });
+
+  test('a redirect is followed to the final address', () async {
+    server = FakeGeminiServer('gemini-test-a');
+    await server.start();
+    final requests = <String>[];
+    answers = server.answer((line, socket) async {
+      requests.add(line);
+      if (line.endsWith('/')) {
+        socket.add(utf8.encode('30 ${await open('/moved.gmi', server)}\r\n'));
+      } else {
+        socket.add(utf8.encode('20 text/gemini\r\narrived'));
+      }
+    });
+
+    final response = await client.fetch(await open('/', server));
+
+    expect(response.status, 20);
+    expect(utf8.decode(response.body!), 'arrived');
+    expect(response.url.path, '/moved.gmi');
+    expect(requests, hasLength(2));
+  });
+
+  test('a redirect loop gives up after five hops', () async {
+    server = FakeGeminiServer('gemini-test-a');
+    await server.start();
+    final requests = <String>[];
+    answers = server.answer((line, socket) async {
+      requests.add(line);
+      socket.add(utf8.encode('30 ${await open('/', server)}\r\n'));
+    });
+
+    await expectLater(
+      client.fetch(await open('/', server)),
+      throwsA(isA<GeminiTooManyRedirects>()),
+    );
+    expect(requests, hasLength(6));
+  });
+
+  test('a redirect away from gemini is returned rather than followed', () async {
+    server = FakeGeminiServer('gemini-test-a');
+    await server.start();
+    answers = server.answer((line, socket) =>
+        socket.add(utf8.encode('30 https://example.com/elsewhere\r\n')));
+
+    final response = await client.fetch(await open('/', server));
+
+    expect(response.isRedirect, isTrue);
+    expect(response.meta, 'https://example.com/elsewhere');
+  });
+
+  test('an unreachable host is one failure', () async {
+    // A port with nothing listening on it, on a host that needs no DNS.
+    final nowhere = Uri.parse('gemini://localhost:1/');
+
+    await expectLater(client.fetch(nowhere), throwsA(isA<GeminiException>()));
+  });
+}