add invite support

Closes #82

lib/controllers/invites.dart

@@ -0,0 +1,117 @@
+import "package:collection/collection.dart";
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:nexus/controllers/client.dart";
+import "package:nexus/controllers/client_state.dart";
+import "package:nexus/helpers/extensions/get_localpart.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/topic.dart";
+import "package:nexus/models/invited_room.dart";
+import "package:nexus/models/room_summary.dart";
+
+/// Pending invites, newest first.
+class InvitesController extends Notifier<IList<RoomSummary>> {
+  @override
+  IList<RoomSummary> build() => .new();
+
+  /// Adds new invites, and removes invites for rooms that have since been
+  /// joined or left.
+  void update(
+    IList<InvitedRoom> invitedRooms, {
+    ISet<String> joinedRooms = const .empty(),
+    ISet<String> leftRooms = const .empty(),
+  }) {
+    final userId = ref.read(ClientStateController.provider)?.userId;
+
+    RoomSummary toSummary(InvitedRoom invite) {
+      final summary = invite.inviteState.fold(
+        RoomSummary(roomId: invite.roomId, membership: .invite),
+        (summary, event) => switch (event.content) {
+          NameContent(:final name) when name.isNotEmpty => summary.copyWith(
+            name: name,
+          ),
+          AvatarContent(:final url) => summary.copyWith(avatarUrl: url),
+          TopicContent(:final topic) when topic.isNotEmpty => summary.copyWith(
+            topic: topic,
+          ),
+          CanonicalAliasContent(:final alias) => summary.copyWith(
+            canonicalAlias: alias,
+          ),
+          JoinRulesContent(:final joinRule) => summary.copyWith(
+            joinRule: joinRule,
+          ),
+          CreateContent(:final type, :final roomVersion) => summary.copyWith(
+            roomType: type,
+            roomVersion: roomVersion,
+          ),
+          EncryptionContent(:final algorithm) => summary.copyWith(
+            encryption: algorithm,
+          ),
+          HistoryVisibilityContent(:final historyVisibility) =>
+            summary.copyWith(
+              worldReadable: historyVisibility == .worldReadable,
+            ),
+          MembershipContent(:final isDirect) when event.stateKey == userId =>
+            summary.copyWith(invitedBy: event.sender, isDirect: isDirect),
+          _ => summary,
+        },
+      );
+
+      // The inviter is only known once the user's own invite has been found
+      final inviterProfile = switch (invite.inviteState
+          .firstWhereOrNull(
+            (event) =>
+                event.type == EventType.membership.type &&
+                event.stateKey == summary.invitedBy,
+          )
+          ?.content) {
+        MembershipContent content => content,
+        _ => null,
+      };
+
+      return summary.copyWith(
+        inviterProfile: inviterProfile,
+        // Direct messages usually have no name, so use the inviter's
+        name:
+            summary.name ??
+            (summary.isDirect
+                ? inviterProfile?.displayName ?? summary.invitedBy?.localpart
+                : null),
+      );
+    }
+
+    final newInvites = invitedRooms.map(toSummary).toIList();
+    final newRoomIds = newInvites.map((invite) => invite.roomId).toISet();
+    final removed = joinedRooms.addAll(leftRooms);
+
+    state = newInvites
+        .addAll(state.where((invite) => !newRoomIds.contains(invite.roomId)))
+        .removeWhere((invite) => removed.contains(invite.roomId));
+  }
+
+  void remove(String roomId) =>
+      state = state.removeWhere((invite) => invite.roomId == roomId);
+
+  Future<void> decline(String roomId) async {
+    await ref.read(ClientController.provider.notifier).leaveRoom(roomId);
+    remove(roomId);
+  }
+
+  /// Declines every invite, removing each as it succeeds. If any fail, the
+  /// first error is thrown once all have finished.
+  Future<void> declineAll() =>
+      Future.wait(state.map((invite) => decline(invite.roomId)));
+
+  static final provider =
+      NotifierProvider<InvitesController, IList<RoomSummary>>(
+        InvitesController.new,
+      );
+}