treewide: small refactors

lib/helpers/extensions/build_event_options.dart

@@ -41,7 +41,7 @@ extension BuildEventOptions on Event {
         .read(PinnedIdsController.provider(roomId))
         .contains(eventId);
 
-    void showReasonDialog({
+    void showReasonSheet({
       required String title,
       required String description,
       required String action,
@@ -235,7 +235,7 @@ extension BuildEventOptions on Event {
           ) &&
           !eventId.isFake)
         PopupMenuItem(
-          onTap: () => showReasonDialog(
+          onTap: () => showReasonSheet(
             title: "Delete Message",
             description:
                 "Are you sure you want to delete this message? "
@@ -260,7 +260,7 @@ extension BuildEventOptions on Event {
         ),
 
       PopupMenuItem(
-        onTap: () => showReasonDialog(
+        onTap: () => showReasonSheet(
           title: "Report",
           description:
               "Report this event to your server administrators, "

lib/helpers/extensions/get_localpart.dart

@@ -1,6 +1,9 @@
 extension GetLocalpart on String {
   String get localpart => length > 1 ? substring(1).split(":").first : "?";
 
+  /// Whether this looks like a valid Matrix user ID, e.g. `@user:example.com`.
+  bool get isValidUserId => RegExp(r"^@[^:\s]+:[^\s]+$").hasMatch(this);
+
   String? get serverName {
     final index = indexOf(":");
     return index == -1 ? null : substring(index + 1);

lib/helpers/extensions/show_about_sheet.dart

@@ -7,8 +7,8 @@ import "package:m3e_card_list/m3e_card_list.dart";
 import "package:nexus/helpers/launch_helper.dart";
 import "package:package_info_plus/package_info_plus.dart";
 
-extension ShowAboutDialog on BuildContext {
-  Future<void> showAboutDialog(WidgetRef ref) async {
+extension ShowAboutSheet on BuildContext {
+  Future<void> showAboutSheet(WidgetRef ref) async {
     final packageInfo = await PackageInfo.fromPlatform();
 
     if (mounted) {

lib/helpers/extensions/show_error_snack_bar.dart

@@ -0,0 +1,28 @@
+import "package:material_ui/material_ui.dart";
+
+extension ShowErrorSnackBar on ScaffoldMessengerState {
+  /// Shows [message] in a snackbar styled as an error.
+  ScaffoldFeatureController<SnackBar, SnackBarClosedReason> showErrorSnackBar(
+    String message, {
+    ({String label, VoidCallback onPressed})? action,
+  }) {
+    final colorScheme = Theme.of(context).colorScheme;
+
+    return showSnackBar(
+      .new(
+        backgroundColor: colorScheme.errorContainer,
+        content: Text(
+          message,
+          style: .new(color: colorScheme.onErrorContainer),
+        ),
+        action: action == null
+            ? null
+            : .new(
+                label: action.label,
+                onPressed: action.onPressed,
+                textColor: colorScheme.onErrorContainer,
+              ),
+      ),
+    );
+  }
+}

lib/helpers/extensions/with_progress_snackbar.dart

@@ -1,4 +1,5 @@
 import "package:material_ui/material_ui.dart";
+import "package:nexus/helpers/extensions/show_error_snack_bar.dart";
 
 extension WithProgressSnackbar on BuildContext {
   /// Shows [progress] in a snackbar while [action] runs, and shows any error
@@ -10,8 +11,6 @@ extension WithProgressSnackbar on BuildContext {
     Future<T> Function() action,
   ) async {
     final messenger = ScaffoldMessenger.of(this);
-    final colorScheme = Theme.of(this).colorScheme;
-
     final snackbar = messenger.showSnackBar(
       .new(content: Text(progress), duration: const .new(days: 1)),
     );
@@ -19,15 +18,7 @@ extension WithProgressSnackbar on BuildContext {
     try {
       return await action();
     } catch (error) {
-      messenger.showSnackBar(
-        .new(
-          backgroundColor: colorScheme.errorContainer,
-          content: Text(
-            error.toString(),
-            style: .new(color: colorScheme.onErrorContainer),
-          ),
-        ),
-      );
+      messenger.showErrorSnackBar(error.toString());
 
       return null;
     } finally {