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/Screens/FilePreviewScreen/TimelineMediaPreviewDataSource.swift

@@ -35,13 +35,19 @@ class TimelineMediaPreviewDataSource: NSObject, QLPreviewControllerDataSource {
     
     var paginationState: TimelinePaginationState
     
+    /// The gallery attachments to include, so that a gallery only contributes the media being browsed.
+    private let allowedGalleryItemTypes: [TimelineAllowedGalleryItemType]?
+    
     /// Builds a data source spanning every previewable attachment in the timeline, paginating
     /// as the user swipes past the loaded range. Used when tapping a standalone media message.
     init(itemViewStates: [RoomTimelineItemViewState],
          initialItem: EventBasedMessageTimelineItemProtocol,
          initialPadding: Int = 100,
-         paginationState: TimelinePaginationState) {
-        previewItems = itemViewStates.compactMap(TimelineMediaPreviewItem.Media.init)
+         paginationState: TimelinePaginationState,
+         allowedGalleryItemTypes: [TimelineAllowedGalleryItemType]? = nil) {
+        self.allowedGalleryItemTypes = allowedGalleryItemTypes
+        
+        previewItems = itemViewStates.flatMap { $0.previewableMedia(allowedGalleryItemTypes: allowedGalleryItemTypes) }
         
         let initialPreviewID = TimelineMediaPreviewItem.Media(timelineItem: initialItem).id
         if let initialItemArrayIndex = previewItems.firstIndex(where: { $0.id == initialPreviewID }) {
@@ -66,6 +72,8 @@ class TimelineMediaPreviewDataSource: NSObject, QLPreviewControllerDataSource {
     /// gallery and there's no timeline pagination to drive.
     init(galleryItem: GalleryRoomTimelineItem,
          initialIndex: Int) {
+        allowedGalleryItemTypes = nil // All of the gallery's attachments are shown.
+        
         let media = galleryItem.content.items.map { item in
             TimelineMediaPreviewItem.Media(galleryParent: galleryItem, item: item)
         }
@@ -93,17 +101,17 @@ class TimelineMediaPreviewDataSource: NSObject, QLPreviewControllerDataSource {
     }
     
     func updatePreviewItems(itemViewStates: [RoomTimelineItemViewState]) {
-        let newItems: [TimelineMediaPreviewItem.Media] = itemViewStates.compactMap { itemViewState in
-            guard let newItem = TimelineMediaPreviewItem.Media(roomTimelineItemViewState: itemViewState) else { return nil }
-            
-            // If an item already exists use that instead to preserve the file handle, download error etc.
-            if let oldItem = previewItems.first(where: { $0.id == newItem.id }) {
-                oldItem.content = newItem.content
-                return oldItem
+        let newItems: [TimelineMediaPreviewItem.Media] = itemViewStates
+            .flatMap { $0.previewableMedia(allowedGalleryItemTypes: allowedGalleryItemTypes) }
+            .map { newItem in
+                // If an item already exists use that instead to preserve the file handle, download error etc.
+                if let oldItem = previewItems.first(where: { $0.id == newItem.id }) {
+                    oldItem.content = newItem.content
+                    return oldItem
+                }
+                
+                return newItem
             }
-            
-            return newItem
-        }
         
         var hasPaginated = false
         if let range = newItems.map(\.id).firstRange(of: previewItems.map(\.id)) {
@@ -430,3 +438,23 @@ enum TimelineMediaPreviewItem: Equatable {
         }
     }
 }
+
+private extension RoomTimelineItemViewState {
+    /// The media of this item that can be previewed, flattening a gallery message into its individual
+    /// attachments so that they can be browsed alongside the timeline's other media.
+    /// - Parameter allowedGalleryItemTypes: Restricts a gallery's attachments to the media being
+    ///   browsed, as the SDK can only filter the gallery event as a whole.
+    func previewableMedia(allowedGalleryItemTypes: [TimelineAllowedGalleryItemType]?) -> [TimelineMediaPreviewItem.Media] {
+        guard case .gallery(let galleryItem) = type else {
+            return [TimelineMediaPreviewItem.Media(roomTimelineItemViewState: self)].compactMap { $0 }
+        }
+        
+        return galleryItem.content.items.filter { item in
+            guard let allowedItemType = item.allowedItemType else {
+                return false // Nothing to preview, and unlike a tile there's no index to line up with.
+            }
+            
+            return allowedGalleryItemTypes?.contains(allowedItemType) ?? true
+        }.map { TimelineMediaPreviewItem.Media(galleryParent: galleryItem, item: $0) }
+    }
+}