Allow previews in the timeline to include filtered galleries (#5943)

* remove the usage of the timeline kind override in favour of getting it properly from the timeline view model

* allow the previews to include gallery items filtered by the allowed types when started outside the gallery

sss

asa

* fix for actions not being forwarded to the timeline right

* pr suggestions

ElementX/Sources/Services/Timeline/TimelineProxyProtocol.swift

@@ -16,7 +16,7 @@ enum TimelineKind: Equatable {
     case pinned
     case thread(rootEventID: String)
     
-    enum MediaPresentation { case roomScreenLive, roomScreenDetached, pinnedEventsScreen, mediaFilesScreen }
+    enum MediaPresentation { case roomScreenLive, roomScreenDetached, roomScreenThread, pinnedEventsScreen, mediaFilesScreen }
     case media(MediaPresentation)
     
     var isThread: Bool {
@@ -42,6 +42,34 @@ enum TimelineFocus {
 
 enum TimelineAllowedMessageType {
     case audio, file, image, video, gallery
+    
+    /// The gallery attachments this type allows, so that a gallery event's attachments can be
+    /// filtered client side to match. A gallery can't contain another gallery, hence the `nil`.
+    var allowedGalleryItemType: TimelineAllowedGalleryItemType? {
+        switch self {
+        case .audio: .audio
+        case .file: .file
+        case .image: .image
+        case .video: .video
+        case .gallery: nil
+        }
+    }
+}
+
+/// The gallery attachments a timeline allows, mirroring the message types it is filtered to. The SDK can
+/// only filter whole events, so a gallery's attachments are filtered by these client side. Unlike a
+/// message type there's no gallery case, as a gallery can't contain another one.
+enum TimelineAllowedGalleryItemType {
+    case audio, file, image, video
+}
+
+extension [TimelineAllowedMessageType] {
+    /// The gallery attachments these types allow, or `nil` when they place no restriction on them,
+    /// which is the case for a timeline made up of galleries alone.
+    var allowedGalleryItemTypes: [TimelineAllowedGalleryItemType]? {
+        let types = compactMap(\.allowedGalleryItemType)
+        return types.isEmpty ? nil : types
+    }
 }
 
 enum TimelineProxyError: Error {