added dialog to collection page

lib/pages/collection_page.dart

@@ -1,13 +1,20 @@
 import 'package:flutter/material.dart';
 
+import '../model/bookmark.dart';
 import '../service/bookmarks_provider.dart';
 import '../service/storage.dart';
+import '../widgets/create_bookmark_dialog.dart';
 
-class CollectionPage extends StatelessWidget {
+class CollectionPage extends StatefulWidget {
   const CollectionPage({super.key});
 
   static const String routeName = '/bookmarks';
 
+  @override
+  State<CollectionPage> createState() => _CollectionPageState();
+}
+
+class _CollectionPageState extends State<CollectionPage> {
   @override
   Widget build(BuildContext context) {
     if (BookmarksProvider.selectedCollectionId == null) {
@@ -17,19 +24,32 @@ class CollectionPage extends StatelessWidget {
       BookmarksProvider.selectedCollectionId!,
     );
 
-    BookmarksProvider.selectedCollectionId == null;
+    final collection = Storage.loadCollections().firstWhere(
+      (c) => c.id == BookmarksProvider.selectedCollectionId,
+    );
 
     return Scaffold(
-      appBar: AppBar(
-        title: Text(
-          Storage.loadCollections()
-              .firstWhere((c) => c.id == BookmarksProvider.selectedCollectionId)
-              .name,
-        ),
-      ),
+      appBar: AppBar(title: Text(collection.name)),
       body: ListView(
         children: bookmarks.map((e) => ListTile(title: Text(e.name))).toList(),
       ),
+      floatingActionButton: FloatingActionButton(
+        onPressed: onAddButtonPressed,
+        child: Icon(Icons.add),
+      ),
     );
   }
+
+  void onAddButtonPressed() => showDialog(
+    context: context,
+    builder: (context) => CreateBookmarkDialog(
+      collectionId: BookmarksProvider.selectedCollectionId!,
+      onSavePressed: onBookmarkSaved,
+    ),
+  );
+
+  void onBookmarkSaved(Bookmark bookmark) {
+    Storage.addBookmark(bookmark);
+    setState(() {});
+  }
 }