Add deduplication

lib/pages/communities_list.dart

@@ -38,6 +38,7 @@ class CommunitiesListPage extends StatelessWidget {
             )
           ],
         ),
+        uniqueProp: (item) => item.community.id,
       ),
     );
   }

lib/pages/inbox.dart

@@ -118,6 +118,7 @@ class InboxPage extends HookWidget {
                 canBeMarkedAsRead: true,
                 hideOnRead: unreadOnly.value,
               ),
+              uniqueProp: (item) => item.comment.id,
             ),
             SortableInfiniteList<PersonMentionView>(
               noItems: const Text('no mentions'),
@@ -135,6 +136,7 @@ class InboxPage extends HookWidget {
                 umv,
                 hideOnRead: unreadOnly.value,
               ),
+              uniqueProp: (item) => item.personMention.id,
             ),
             InfiniteScroll<PrivateMessageView>(
               noItems: const Padding(
@@ -154,6 +156,7 @@ class InboxPage extends HookWidget {
                 privateMessageView: mv,
                 hideOnRead: unreadOnly.value,
               ),
+              uniqueProp: (item) => item.privateMessage.id,
             ),
           ],
         ),

lib/pages/search_results.dart

@@ -120,6 +120,20 @@ class _SearchResultsList extends HookWidget {
             throw UnimplementedError();
         }
       },
+      uniqueProp: (item) {
+        switch (type) {
+          case SearchType.comments:
+            return (item as CommentView).comment.id;
+          case SearchType.communities:
+            return (item as CommunityView).community.id;
+          case SearchType.posts:
+            return (item as PostView).post.id;
+          case SearchType.users:
+            return (item as PersonViewSafe).person.id;
+          default:
+            return item;
+        }
+      },
     );
   }
 }

lib/widgets/infinite_scroll.dart

@@ -1,3 +1,5 @@
+import 'dart:collection';
+
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
@@ -47,6 +49,10 @@ class InfiniteScroll<T> extends HookWidget {
   /// Widget that will be displayed if there are no items
   final Widget noItems;
 
+  /// Maps an item to its unique property that will allow to detect possible
+  /// duplicates thus perfoming deduplication
+  final Object Function(T item) uniqueProp;
+
   const InfiniteScroll({
     this.batchSize = 10,
     this.leading = const SizedBox.shrink(),
@@ -57,6 +63,7 @@ class InfiniteScroll<T> extends HookWidget {
     @required this.fetcher,
     this.controller,
     this.noItems = const SizedBox.shrink(),
+    this.uniqueProp,
   })  : assert(itemBuilder != null),
         assert(fetcher != null),
         assert(batchSize > 0);
@@ -64,6 +71,8 @@ class InfiniteScroll<T> extends HookWidget {
   @override
   Widget build(BuildContext context) {
     final data = useState<List<T>>([]);
+    // holds unique props of the data
+    final dataSet = useRef(HashSet<Object>());
     final hasMore = useRef(true);
     final isFetching = useRef(false);
 
@@ -111,13 +120,19 @@ class InfiniteScroll<T> extends HookWidget {
             // if it's already fetching more, skip
             if (!isFetching.current) {
               isFetching.current = true;
-              fetcher(page, batchSize).then((newData) {
+              fetcher(page, batchSize).then((incoming) {
                 // if got less than the batchSize, mark the list as done
-                if (newData.length < batchSize) {
+                if (incoming.length < batchSize) {
                   hasMore.current = false;
                 }
+
+                final newData = incoming.where(
+                  (e) => !dataSet.current.contains(uniqueProp?.call(e) ?? e),
+                );
+
                 // append new data
                 data.value = [...data.value, ...newData];
+                dataSet.current.addAll(newData.map(uniqueProp ?? (e) => e));
               }).whenComplete(() => isFetching.current = false);
             }
 

lib/widgets/sortable_infinite_list.dart

@@ -20,6 +20,7 @@ class SortableInfiniteList<T> extends HookWidget {
   final Function onStyleChange;
   final Widget noItems;
   final SortType defaultSort;
+  final Object Function(T item) uniqueProp;
 
   const SortableInfiniteList({
     @required this.fetcher,
@@ -28,6 +29,7 @@ class SortableInfiniteList<T> extends HookWidget {
     this.onStyleChange,
     this.noItems,
     this.defaultSort = SortType.active,
+    this.uniqueProp,
   })  : assert(fetcher != null),
         assert(itemBuilder != null),
         assert(defaultSort != null);
@@ -56,49 +58,41 @@ class SortableInfiniteList<T> extends HookWidget {
       controller: isc,
       batchSize: 20,
       noItems: noItems,
+      uniqueProp: uniqueProp,
     );
   }
 }
 
-class InfinitePostList extends StatelessWidget {
-  final FetcherWithSorting<PostView> fetcher;
-  final InfiniteScrollController controller;
-
-  const InfinitePostList({
-    @required this.fetcher,
-    this.controller,
-  }) : assert(fetcher != null);
-
-  Widget build(BuildContext context) => SortableInfiniteList<PostView>(
-        onStyleChange: () {},
-        itemBuilder: (post) => Column(
-          children: [
-            PostWidget(post),
-            const SizedBox(height: 20),
-          ],
-        ),
-        fetcher: fetcher,
-        controller: controller,
-        noItems: const Text('there are no posts'),
-      );
+class InfinitePostList extends SortableInfiniteList<PostView> {
+  InfinitePostList({
+    @required FetcherWithSorting<PostView> fetcher,
+    InfiniteScrollController controller,
+  }) : super(
+          itemBuilder: (post) => Column(
+            children: [
+              PostWidget(post),
+              const SizedBox(height: 20),
+            ],
+          ),
+          fetcher: fetcher,
+          controller: controller,
+          noItems: const Text('there are no posts'),
+          uniqueProp: (item) => item.post.id,
+        );
 }
 
-class InfiniteCommentList extends StatelessWidget {
-  final FetcherWithSorting<CommentView> fetcher;
-  final InfiniteScrollController controller;
-
-  const InfiniteCommentList({
-    @required this.fetcher,
-    this.controller,
-  }) : assert(fetcher != null);
-
-  Widget build(BuildContext context) => SortableInfiniteList<CommentView>(
-        itemBuilder: (comment) => CommentWidget(
-          CommentTree(comment),
-          detached: true,
-        ),
-        fetcher: fetcher,
-        controller: controller,
-        noItems: const Text('there are no comments'),
-      );
+class InfiniteCommentList extends SortableInfiniteList<CommentView> {
+  InfiniteCommentList({
+    @required FetcherWithSorting<CommentView> fetcher,
+    InfiniteScrollController controller,
+  }) : super(
+          itemBuilder: (comment) => CommentWidget(
+            CommentTree(comment),
+            detached: true,
+          ),
+          fetcher: fetcher,
+          controller: controller,
+          noItems: const Text('there are no comments'),
+          uniqueProp: (item) => item.comment.id,
+        );
 }