add support for initializing and resetting crypto identity

Fixes #137

lib/widgets/recovery_key_sheet.dart

@@ -0,0 +1,145 @@
+import "dart:async";
+
+import "package:flutter/services.dart";
+import "package:flutter_hooks/flutter_hooks.dart";
+import "package:hooks_riverpod/hooks_riverpod.dart";
+import "package:material_ui/material_ui.dart";
+import "package:nexus/controllers/client.dart";
+import "package:nexus/controllers/client_state.dart";
+import "package:nexus/helpers/launch_helper.dart";
+import "package:nexus/models/gomuks_exception.dart";
+import "package:nexus/models/recovery_key.dart";
+import "package:nexus/widgets/sheet_layout.dart";
+
+/// Shows a newly generated recovery key, and once the user confirms they've
+/// saved it, resets encryption with it. Pops with true if that succeeded.
+class const RecoveryKeySheet(
+  final RecoveryKey recoveryKey, {
+  required final bool isReset,
+  super.key,
+}) extends HookConsumerWidget {
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final saved = useState(false);
+    final isLoading = useState(false);
+    final error = useState<String?>(null);
+    final needsApproval = useState(false);
+    final approvalUrl = useState<Uri?>(null);
+    final colorScheme = Theme.of(context).colorScheme;
+
+    Future<void> reset() async {
+      if (isLoading.value) return;
+      isLoading.value = true;
+      error.value = null;
+      try {
+        await ref
+            .read(ClientController.provider.notifier)
+            .resetEncryption(recoveryKey);
+        if (context.mounted) Navigator.of(context).pop(true);
+      } catch (resetError) {
+        if (resetError case GomuksException(statusCode: 401)) {
+          // Open the approval page straight away the first time.
+          if (!needsApproval.value) {
+            needsApproval.value = true;
+            final homeserver = ref
+                .read(ClientStateController.provider)
+                ?.homeserverUrl;
+            final url = homeserver == null
+                ? null
+                : await ref
+                      .read(ClientController.provider.notifier)
+                      .getCrossSigningResetUrl(.parse(homeserver))
+                      .onError((_, _) => null);
+            if (!context.mounted || url == null) return;
+
+            approvalUrl.value = url;
+            await ref.read(LaunchHelper.provider).launchUrl(url);
+          }
+        } else {
+          error.value = resetError.toString();
+        }
+      } finally {
+        if (context.mounted) isLoading.value = false;
+      }
+    }
+
+    // Approval happens on a web page that can't redirect back, so keep retrying
+    // in the background until it goes through, or the sheet is closed.
+    useEffect(() {
+      if (!needsApproval.value) return null;
+      return Timer.periodic(const .new(seconds: 3), (_) => reset()).cancel;
+    }, [needsApproval.value]);
+
+    return SheetLayout(
+      title: const Text("Save Your Recovery Key"),
+      actions: [
+        TextButton(
+          onPressed: () => Navigator.of(context).pop(false),
+          child: const Text("Cancel"),
+        ),
+        TextButton(
+          onPressed: !saved.value || isLoading.value ? null : reset,
+          style: isReset
+              ? TextButton.styleFrom(foregroundColor: colorScheme.error)
+              : null,
+          child: Text(
+            needsApproval.value
+                ? "Try Again"
+                : isReset
+                ? "Reset"
+                : "Set Up",
+          ),
+        ),
+      ],
+      children: [
+        const Text(
+          "This is your new recovery key. Store it somewhere safe, like a password manager. You'll need it to verify new sessions.",
+        ),
+        Card.filled(
+          child: ListTile(
+            title: SelectableText(
+              recoveryKey.recoveryKey,
+              style: const .new(fontFamily: "bundled-mono"),
+            ),
+            trailing: IconButton(
+              tooltip: "Copy recovery key",
+              onPressed: () =>
+                  Clipboard.setData(.new(text: recoveryKey.recoveryKey)),
+              icon: const Icon(Icons.copy),
+            ),
+          ),
+        ),
+        CheckboxListTile(
+          value: saved.value,
+          onChanged: (value) => saved.value = value ?? false,
+          title: const Text("I've saved my recovery key"),
+        ),
+        AnimatedSize(
+          duration: Durations.medium2,
+          curve: Curves.easeInOut,
+          alignment: .topCenter,
+          child: needsApproval.value
+              ? Column(
+                  crossAxisAlignment: .stretch,
+                  spacing: 8,
+                  children: [
+                    const Text(
+                      "Your homeserver needs you to approve resetting your identity in your account settings. Once you've approved it, come back here and the reset will finish automatically.",
+                    ),
+                    if (approvalUrl.value case final url?)
+                      OutlinedButton.icon(
+                        onPressed: () =>
+                            ref.read(LaunchHelper.provider).launchUrl(url),
+                        icon: const Icon(Icons.open_in_new),
+                        label: const Text("Approve in account settings"),
+                      ),
+                  ],
+                )
+              : const SizedBox(width: .infinity),
+        ),
+        if (error.value case final message?)
+          Text(message, style: .new(color: colorScheme.error)),
+      ],
+    );
+  }
+}