add diffing for a lot of events

lib/widgets/renderers/change_line.dart

@@ -0,0 +1,72 @@
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:material_ui/material_ui.dart";
+
+/// A line of what a state event changed, like a room's old name, struck
+/// through, then its new one.
+class const ChangeLine({
+  /// What changed, e.g. `Denied`, in bold before the items.
+  final String? label,
+  final IList<String> removed = const .empty(),
+  final IList<String> added = const .empty(),
+  required final Color removedColor,
+  required final Color addedColor,
+
+  /// Whether to quote the items, like server names, but not whole sentences.
+  final bool quoted = true,
+
+  /// Shown after the items, like a change that isn't one of them.
+  final List<Widget> trailing = const [],
+
+  /// How many removed and how many added items to show, as some events, like
+  /// a room's first server ACL, can change hundreds.
+  final int maxShown = 5,
+
+  /// The most lines each item can take, as some, like topics, can be long.
+  final int maxLines = 2,
+  super.key,
+}) extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    final style = theme.textTheme.labelMedium;
+
+    Iterable<Widget> items(
+      IList<String> items, {
+      required Color color,
+      required bool struck,
+    }) => [
+      ...items
+          .take(maxShown)
+          .map(
+            (item) => Text(
+              quoted ? "\"$item\"" : item,
+              maxLines: maxLines,
+              overflow: .ellipsis,
+              style: style?.copyWith(
+                color: color,
+                decoration: struck ? .lineThrough : null,
+                decorationColor: color,
+              ),
+            ),
+          ),
+      if (items.length > maxShown)
+        Text(
+          "+${items.length - maxShown} more",
+          style: style?.copyWith(color: theme.colorScheme.onSurfaceVariant),
+        ),
+    ];
+
+    return Wrap(
+      spacing: 8,
+      runSpacing: 2,
+      crossAxisAlignment: .center,
+      children: [
+        if (label case final label?)
+          Text(label, style: style?.copyWith(fontWeight: .bold)),
+        ...items(removed, color: removedColor, struck: true),
+        ...items(added, color: addedColor, struck: false),
+        ...trailing,
+      ],
+    );
+  }
+}

lib/widgets/renderers/event.dart

@@ -9,14 +9,17 @@ import "package:nexus/controllers/rooms.dart";
 import "package:nexus/controllers/settings.dart";
 import "package:nexus/helpers/extensions/is_shown_as_message.dart";
 import "package:nexus/helpers/extensions/show_adaptive_menu.dart";
+import "package:nexus/helpers/extensions/success_scheme.dart";
 import "package:nexus/helpers/hooks/chat_scroll.dart";
 import "package:nexus/models/content/avatar.dart";
 import "package:nexus/models/content/canonical_alias.dart";
 import "package:nexus/models/content/content.dart";
 import "package:nexus/models/content/create.dart";
+import "package:nexus/models/content/encryption.dart";
 import "package:nexus/models/content/history_visibility.dart";
 import "package:nexus/models/content/join_rules.dart";
 import "package:nexus/models/content/membership.dart";
+import "package:nexus/models/content/name.dart";
 import "package:nexus/models/content/pinned_events.dart";
 import "package:nexus/models/content/power_levels.dart";
 import "package:nexus/models/content/server_acl.dart";
@@ -28,7 +31,10 @@ import "package:nexus/widgets/renderers/message.dart";
 import "package:nexus/widgets/reaction_row.dart";
 import "package:nexus/widgets/read_receipts_row.dart";
 import "package:nexus/widgets/renderers/membership.dart";
+import "package:nexus/widgets/renderers/change_line.dart";
 import "package:nexus/widgets/renderers/generic_event.dart";
+import "package:nexus/widgets/renderers/join_rules_diff.dart";
+import "package:nexus/widgets/renderers/power_levels_diff.dart";
 import "package:nexus/widgets/renderers/pinned_events_diff.dart";
 import "package:nexus/widgets/renderers/server_acl_diff.dart";
 import "package:nexus/widgets/swipe_to_reply.dart";
@@ -105,6 +111,10 @@ class const EventRenderer(
         event.sender == previousEvent?.sender &&
         event.pmp?.id == previousEvent?.pmp?.id;
 
+    // For what a state event changed, from and to
+    final removedColor = colorScheme.error;
+    final addedColor = theme.successScheme.primary;
+
     GenericEventRenderer generic(
       IconData icon,
       String text, {
@@ -167,18 +177,57 @@ class const EventRenderer(
               "changed the room avatar",
             ),
             CreateContent() => generic(Icons.add, "created the room"),
-            PowerLevelsContent() => generic(
+            final PowerLevelsContent content => generic(
               Icons.power,
               "changed the room's power levels",
+              details: [
+                PowerLevelsDiff(
+                  roomId,
+                  content,
+                  previous: switch (event.previousContent) {
+                    final PowerLevelsContent previous => previous,
+                    _ => null,
+                  },
+                ),
+              ],
             ),
-            JoinRulesContent() => generic(
+            final JoinRulesContent content => generic(
               Icons.rule,
               "changed the room's join rules",
+              details: [
+                JoinRulesDiff(
+                  content,
+                  previous: switch (event.previousContent) {
+                    final JoinRulesContent previous => previous,
+                    _ => null,
+                  },
+                ),
+              ],
             ),
-            TopicContent() => generic(
-              Icons.description,
-              "updated the room topic",
-            ),
+            TopicContent(:final topic) => () {
+              final previous = switch (event.previousContent) {
+                TopicContent(:final topic) when topic.isNotEmpty => topic,
+                _ => null,
+              };
+
+              return generic(
+                Icons.description,
+                topic.isEmpty
+                    ? "removed the room topic"
+                    : previous == null
+                    ? "set the room topic"
+                    : "changed the room topic",
+                details: [
+                  ChangeLine(
+                    removed: [?previous].lock,
+                    added: [if (topic.isNotEmpty) topic].lock,
+                    removedColor: removedColor,
+                    addedColor: addedColor,
+                    quoted: false,
+                  ),
+                ],
+              );
+            }(),
             HistoryVisibilityContent(:final historyVisibility) => generic(
               Icons.history,
               "changed the room's history visibility to ${switch (historyVisibility) {
@@ -230,32 +279,71 @@ class const EventRenderer(
                 ),
               ],
             ),
-            CanonicalAliasContent(:final alias, :final altAliases) => generic(
-              Icons.numbers,
-              switch ([
-                if (event.previousContent case CanonicalAliasContent(
-                  alias: final prevAlias,
-                  altAliases: final prevAltAliases,
-                )) ...[
-                  if (prevAlias != alias)
-                    if (alias == null)
-                      "removed the room's canonical alias"
-                    else
-                      "changed the room's canonical alias to $alias",
+            CanonicalAliasContent(:final alias, :final altAliases) => () {
+              final previous = switch (event.previousContent) {
+                final CanonicalAliasContent previous => previous,
+                _ => null,
+              };
+              final previousAltAliases =
+                  previous?.altAliases ?? const ISet<String>.empty();
 
-                  if (prevAltAliases
-                          .remove(alias ?? "")
-                          .remove(prevAlias ?? "") !=
-                      altAliases.remove(alias ?? "").remove(prevAlias ?? ""))
-                    "changed the room's aliases",
-                ] else ...[
-                  if (alias != null) "set the room's canonical alias",
-                  if (altAliases.isNotEmpty) "set the room's aliases",
+              return generic(
+                Icons.numbers,
+                previous == null
+                    ? "set the room's aliases"
+                    : "changed the room's aliases",
+                details: [
+                  if (previous?.alias != alias)
+                    ChangeLine(
+                      label: "Canonical alias",
+                      removed: [?previous?.alias].lock,
+                      added: [?alias].lock,
+                      removedColor: removedColor,
+                      addedColor: addedColor,
+                    ),
+                  if (previousAltAliases != altAliases)
+                    ChangeLine(
+                      label: "Aliases",
+                      removed: previousAltAliases
+                          .difference(altAliases)
+                          .toIList(),
+                      added: altAliases
+                          .difference(previousAltAliases)
+                          .toIList(),
+                      removedColor: removedColor,
+                      addedColor: addedColor,
+                    ),
                 ],
-              ]) {
-                [] => "did something related to room aliases",
-                List prev => prev.join(" and "),
-              },
+              );
+            }(),
+            NameContent(:final name) => () {
+              final previous = switch (event.previousContent) {
+                NameContent(:final name) when name.isNotEmpty => name,
+                _ => null,
+              };
+
+              return generic(
+                Icons.title,
+                name.isEmpty
+                    ? "removed the room name"
+                    : previous == null
+                    ? "set the room name"
+                    : "changed the room name",
+                details: [
+                  ChangeLine(
+                    removed: [?previous].lock,
+                    added: [if (name.isNotEmpty) name].lock,
+                    removedColor: removedColor,
+                    addedColor: addedColor,
+                  ),
+                ],
+              );
+            }(),
+            EncryptionContent() => generic(
+              Icons.lock,
+              event.previousContent is EncryptionContent
+                  ? "changed the room's encryption settings"
+                  : "enabled encryption",
             ),
             _ => null,
           };

lib/widgets/renderers/join_rules_diff.dart

@@ -0,0 +1,72 @@
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:hooks_riverpod/hooks_riverpod.dart";
+import "package:material_ui/material_ui.dart";
+import "package:nexus/controllers/rooms.dart";
+import "package:nexus/helpers/extensions/join_rule_name.dart";
+import "package:nexus/helpers/extensions/success_scheme.dart";
+import "package:nexus/models/content/join_rules.dart";
+import "package:nexus/widgets/renderers/change_line.dart";
+
+/// The join rule a join rules event changed to, and for restricted rooms, the
+/// rooms whose members it let join, or stopped letting join.
+class const JoinRulesDiff(
+  final JoinRulesContent content, {
+  final JoinRulesContent? previous,
+  super.key,
+}) extends ConsumerWidget {
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final theme = Theme.of(context);
+    final removedColor = theme.colorScheme.error;
+    final addedColor = theme.successScheme.primary;
+
+    ISet<String> roomIdsOf(JoinRulesContent? content) =>
+        (content?.allow ?? const ISet<AllowCondition>.empty())
+            .map((condition) => condition.roomId)
+            .nonNulls
+            .toISet();
+    final before = roomIdsOf(previous);
+    final after = roomIdsOf(content);
+    final removed = before.difference(after);
+    final added = after.difference(before);
+
+    // Rooms the user isn't in are shown by ID
+    final names = ref.watch(
+      RoomsController.provider.select(
+        (rooms) => IMap.fromEntries(
+          removed
+              .addAll(added)
+              .map(
+                (roomId) =>
+                    MapEntry(roomId, rooms[roomId]?.metadata?.name ?? roomId),
+              ),
+        ),
+      ),
+    );
+    IList<String> named(ISet<String> roomIds) =>
+        roomIds.map((roomId) => names[roomId] ?? roomId).toIList();
+
+    return Column(
+      crossAxisAlignment: .start,
+      spacing: 2,
+      children: [
+        if (previous?.joinRule != content.joinRule)
+          ChangeLine(
+            removed: [?previous?.joinRule.displayName].lock,
+            added: [content.joinRule.displayName].lock,
+            removedColor: removedColor,
+            addedColor: addedColor,
+            quoted: false,
+          ),
+        if (removed.isNotEmpty || added.isNotEmpty)
+          ChangeLine(
+            label: "Members of",
+            removed: named(removed),
+            added: named(added),
+            removedColor: removedColor,
+            addedColor: addedColor,
+          ),
+      ],
+    );
+  }
+}

lib/widgets/renderers/power_levels_diff.dart

@@ -0,0 +1,141 @@
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:hooks_riverpod/hooks_riverpod.dart";
+import "package:material_ui/material_ui.dart";
+import "package:nexus/controllers/user.dart";
+import "package:nexus/helpers/extensions/displayname_color.dart";
+import "package:nexus/helpers/extensions/get_localpart.dart";
+import "package:nexus/helpers/extensions/success_scheme.dart";
+import "package:nexus/models/content/power_levels.dart";
+import "package:nexus/models/power_level_permission.dart";
+
+/// Whose power levels, and which permissions' levels, a power levels event
+/// changed, in green when raised, and red when lowered.
+class const PowerLevelsDiff(
+  final String roomId,
+  final PowerLevelsContent content, {
+  final PowerLevelsContent? previous,
+  super.key,
+}) extends ConsumerWidget {
+  static const maxShown = 5;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final theme = Theme.of(context);
+    final style = theme.textTheme.labelMedium;
+    final before = previous ?? PowerLevelsContent();
+
+    Text levels(int? from, int? to, {int? fromLevel, int? toLevel}) => Text(
+      "${from ?? "Default"} → ${to ?? "Default"}",
+      style: style?.copyWith(
+        color: switch ((fromLevel ?? from, toLevel ?? to)) {
+          (final from?, final to?) when to > from =>
+            theme.successScheme.primary,
+          (final from?, final to?) when to < from => theme.colorScheme.error,
+          _ => theme.colorScheme.onSurfaceVariant,
+        },
+      ),
+    );
+
+    Iterable<Widget> capped(Iterable<Widget> lines) {
+      final list = lines.toList();
+      return [
+        ...list.take(maxShown),
+        if (list.length > maxShown)
+          Text(
+            "+${list.length - maxShown} more",
+            style: style?.copyWith(color: theme.colorScheme.onSurfaceVariant),
+          ),
+      ];
+    }
+
+    final users = before.users.keys
+        .toISet()
+        .addAll(content.users.keys)
+        .map(
+          (userId) => (
+            userId,
+            from: before.users[userId],
+            to: content.users[userId],
+            fromLevel: before.users[userId] ?? before.usersDefault,
+            toLevel: content.users[userId] ?? content.usersDefault,
+          ),
+        )
+        .where((change) => change.from != change.to)
+        // The most powerful first
+        .toIList()
+        .sort((a, b) => b.toLevel.compareTo(a.toLevel));
+
+    final permissions = <(String, int?, int?)>[
+      ...PowerLevelPermission.values.map(
+        (permission) => (
+          permission.title,
+          permission.levelIn(before),
+          permission.levelIn(content),
+        ),
+      ),
+      ...before.events.keys
+          .toISet()
+          .addAll(content.events.keys)
+          .map(
+            (type) => (
+              PowerLevelEvent.of(type)?.title ?? type,
+              before.events[type],
+              content.events[type],
+            ),
+          ),
+    ].where((permission) => permission.$2 != permission.$3);
+
+    return Column(
+      crossAxisAlignment: .start,
+      spacing: 2,
+      children: [
+        ...capped(
+          users.map(
+            (change) => Wrap(
+              spacing: 8,
+              crossAxisAlignment: .center,
+              children: [
+                Text(
+                  ref
+                          .watch(
+                            UserController.provider(
+                              .new(roomId: roomId, userId: change.$1),
+                            ),
+                          )
+                          .value
+                          ?.displayName ??
+                      change.$1.localpart,
+                  style: style?.copyWith(
+                    fontWeight: .bold,
+                    color: ref.displaynameColorAt(
+                      change.$1,
+                      change.toLevel.toDouble(),
+                    ),
+                  ),
+                ),
+                levels(
+                  change.from,
+                  change.to,
+                  fromLevel: change.fromLevel,
+                  toLevel: change.toLevel,
+                ),
+              ],
+            ),
+          ),
+        ),
+        ...capped(
+          permissions.map(
+            (permission) => Wrap(
+              spacing: 8,
+              crossAxisAlignment: .center,
+              children: [
+                Text(permission.$1, style: style?.copyWith(fontWeight: .bold)),
+                levels(permission.$2, permission.$3),
+              ],
+            ),
+          ),
+        ),
+      ],
+    );
+  }
+}

lib/widgets/renderers/server_acl_diff.dart

@@ -2,6 +2,7 @@ import "package:fast_immutable_collections/fast_immutable_collections.dart";
 import "package:material_ui/material_ui.dart";
 import "package:nexus/helpers/extensions/success_scheme.dart";
 import "package:nexus/models/content/server_acl.dart";
+import "package:nexus/widgets/renderers/change_line.dart";
 
 /// The servers newly denied (in red) and allowed (in green) by a server ACL
 /// event, and those no longer denied or allowed, struck through.
@@ -10,13 +11,9 @@ class const ServerAclDiff(
   final ServerACLContent? previous,
   super.key,
 }) extends StatelessWidget {
-  static const maxShown = 5;
-
   @override
   Widget build(BuildContext context) {
     final theme = Theme.of(context);
-    final style = theme.textTheme.labelMedium;
-    final colorScheme = theme.colorScheme;
 
     final ipLiteralsAllowed = switch (previous) {
       final previous?
@@ -32,43 +29,24 @@ class const ServerAclDiff(
       IList<String> after, {
       required bool ipLiterals,
     }) {
+      // Sets, as an ACL can list hundreds of servers
       final beforeSet = before.toISet();
       final afterSet = after.toISet();
-      final servers = [
-        ...after
-            .where((server) => !beforeSet.contains(server))
-            .map((server) => (server, removed: false)),
-        ...before
-            .where((server) => !afterSet.contains(server))
-            .map((server) => (server, removed: true)),
-      ];
-      if (servers.isEmpty && !ipLiterals) return null;
+      final removed = before.where((server) => !afterSet.contains(server));
+      final added = after.where((server) => !beforeSet.contains(server));
+      if (removed.isEmpty && added.isEmpty && !ipLiterals) return null;
 
-      return Wrap(
-        spacing: 8,
-        runSpacing: 2,
-        children: [
-          Text(label, style: style?.copyWith(fontWeight: .bold)),
-          ...servers
-              .take(maxShown)
-              .map(
-                (server) => Text(
-                  "\"${server.$1}\"",
-                  style: style?.copyWith(
-                    color: color,
-                    decoration: server.removed ? .lineThrough : null,
-                  ),
-                ),
-              ),
-          if (servers.length > maxShown)
-            Text(
-              "+${servers.length - maxShown} more",
-              style: style?.copyWith(color: colorScheme.onSurfaceVariant),
-            ),
+      return ChangeLine(
+        label: label,
+        removed: .new(removed),
+        added: .new(added),
+        removedColor: color,
+        addedColor: color,
+        trailing: [
           if (ipLiterals)
             Text(
               "servers using IP addresses",
-              style: style?.copyWith(color: color),
+              style: theme.textTheme.labelMedium?.copyWith(color: color),
             ),
         ],
       );
@@ -80,7 +58,7 @@ class const ServerAclDiff(
       children: [
         ?listDiff(
           "Denied",
-          colorScheme.error,
+          theme.colorScheme.error,
           previous?.deny ?? const .empty(),
           content.deny,
           ipLiterals: ipLiteralsAllowed == false,