Add reusable two-factor verification for login and money operations (#32)

frontend/app/lib/security/challenge.dart

@@ -0,0 +1,116 @@
+import 'package:flutter/material.dart';
+
+import 'package:go_router/go_router.dart';
+
+import 'package:sxchnge_analytics/sxchnge_analytics.dart';
+
+import 'package:sxchnge_auth/sxchnge_auth.dart';
+
+import '../generated/i18n/app_localizations.dart';
+
+class FactorRouteRequest {
+  const FactorRouteRequest(this.provider, this.summary);
+  final TwoFactorProvider provider;
+  final Widget? summary;
+}
+
+Future<FactorGrant?> verifyFactor(
+  BuildContext context, {
+  required FactorChallenge challenge,
+  required TwoFactorService service,
+  required JourneyRecorder recorder,
+  required JourneyKind journey,
+  Widget? summary,
+}) async {
+  final provider = TwoFactorProvider(
+    service,
+    challenge,
+    recorder: recorder,
+    journey: journey,
+  );
+  FactorGrant? result;
+  try {
+    result = await context.push<FactorGrant>(
+      '/two-factor',
+      extra: FactorRouteRequest(provider, summary),
+    );
+    return result;
+  } finally {
+    if (result == null) {
+      final step = recorder.begin(
+        journey,
+        JourneyStep.factorVerification,
+        simulated: service.isSimulated,
+      );
+      recorder.finish(step, cancelled: true, simulated: service.isSimulated);
+    }
+    provider.dispose();
+  }
+}
+
+String factorErrorText(AppLocalizations l, FactorError error) =>
+    switch (error) {
+      FactorError.invalid => l.factorInvalid,
+      FactorError.expired => l.factorExpired,
+      FactorError.locked => l.factorLocked,
+      FactorError.cooldown => l.factorWait,
+      FactorError.required => l.factorRequired,
+      FactorError.unavailable => l.factorUnavailable,
+    };
+
+class FactorRoute extends StatefulWidget {
+  const FactorRoute({super.key, required this.request});
+  final FactorRouteRequest request;
+  @override
+  State<FactorRoute> createState() => _FactorRouteState();
+}
+
+class _FactorRouteState extends State<FactorRoute> {
+  FactorRouteRequest get request => widget.request;
+  @override
+  void dispose() {
+    request.provider.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final l = AppLocalizations.of(context)!;
+    final purpose = request.provider.challenge.purpose;
+    final purposeText = switch (purpose) {
+      FactorPurpose.login => l.factorLogin,
+      FactorPurpose.enable => l.factorEnableHelp,
+      FactorPurpose.disable => l.factorDisableHelp,
+      _ => l.factorMoney,
+    };
+    final methodText = request.provider.challenge.method == FactorMethod.email
+        ? l.factorEmail
+        : l.factorAuthenticator;
+    return TwoFactorPage(
+      provider: request.provider,
+      summary: request.summary,
+      labels: TwoFactorLabels(
+        title: l.factorTitle,
+        description: '$purposeText $methodText',
+        code: l.factorCode,
+        confirm: l.factorConfirm,
+        cancel: l.wClose,
+        resend: l.factorResend,
+        expired: request.provider.challenge.method == FactorMethod.email
+            ? l.factorExpired
+            : l.factorAppExpired,
+        help: request.provider.challenge.method == FactorMethod.email
+            ? l.factorHelp
+            : l.factorAppHelp,
+        errorText: (error) =>
+            error == FactorError.expired &&
+                request.provider.challenge.method == FactorMethod.authenticator
+            ? l.factorAppExpired
+            : factorErrorText(l, error),
+        cooldownText: (seconds) => l.factorCooldown(seconds),
+      ),
+      onVerified: (grant) => context.pop(grant),
+      onCancel: () => context.pop(),
+    );
+  }
+}