Implement link previews for text messages using Apple's LinkPreview framework (#4520)

ElementX/Sources/Services/LinkMetadata/LinkMetadataProvider.swift

@@ -0,0 +1,27 @@
+//
+// Copyright 2025 New Vector Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+// Please see LICENSE files in the repository root for full details.
+//
+
+import LinkPresentation
+
+class LinkMetadataProvider: LinkMetadataProviderProtocol {
+    private(set) var metadataItems = [URL: LinkMetadataProviderItem]()
+    
+    func fetchMetadataFor(url: URL) async -> Result<LinkMetadataProviderItem, Error> {
+        if let item = metadataItems[url] {
+            return .success(item)
+        }
+        
+        do {
+            let metadata = try await LPMetadataProvider().startFetchingMetadata(for: url)
+            let item = LinkMetadataProviderItem(url: url, metadata: metadata)
+            metadataItems[url] = item
+            return .success(item)
+        } catch {
+            return .failure(error)
+        }
+    }
+}

ElementX/Sources/Services/LinkMetadata/LinkMetadataProviderProtocol.swift

@@ -0,0 +1,20 @@
+//
+// Copyright 2025 New Vector Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+// Please see LICENSE files in the repository root for full details.
+//
+
+import Foundation
+import LinkPresentation
+
+struct LinkMetadataProviderItem {
+    let url: URL
+    let metadata: LPLinkMetadata?
+}
+
+protocol LinkMetadataProviderProtocol {
+    var metadataItems: [URL: LinkMetadataProviderItem] { get }
+    
+    func fetchMetadataFor(url: URL) async -> Result<LinkMetadataProviderItem, Error>
+}

ElementX/Sources/Services/Timeline/TimelineItems/Items/Messages/TextRoomTimelineItem.swift

@@ -5,6 +5,7 @@
 // Please see LICENSE files in the repository root for full details.
 //
 
+import Algorithms
 import UIKit
 
 struct TextRoomTimelineItem: TextBasedRoomTimelineItem, Equatable {
@@ -28,4 +29,28 @@ struct TextRoomTimelineItem: TextBasedRoomTimelineItem, Equatable {
     var contentType: EventBasedMessageTimelineItemContentType {
         .text(content)
     }
+    
+    var links: [URL] {
+        guard let attributedString = content.formattedBody else {
+            return []
+        }
+        
+        let links = attributedString.runs.compactMap { (run: AttributedString.Runs.Run) -> URL? in
+            if run.link == nil {
+                return nil
+            }
+            
+            guard run.elementX.eventOnRoomAlias == nil,
+                  run.elementX.eventOnRoomID == nil,
+                  run.elementX.roomAlias == nil,
+                  run.elementX.roomID == nil,
+                  run.elementX.userID == nil else {
+                return nil
+            }
+            
+            return run.link
+        }
+        
+        return Array(links.uniqued())
+    }
 }

ElementX/Sources/Services/Timeline/TimelineItems/RoomTimelineItemView.swift

@@ -6,6 +6,8 @@
 //
 import SwiftUI
 
+import OrderedCollections
+
 struct RoomTimelineItemView: View {
     @Environment(\.timelineContext) var context
     @ObservedObject var viewState: RoomTimelineItemViewState
@@ -26,7 +28,7 @@ struct RoomTimelineItemView: View {
     @ViewBuilder private var timelineView: some View {
         switch viewState.type {
         case .text(let item):
-            TextRoomTimelineView(timelineItem: item)
+            TextRoomTimelineView(timelineItem: item, linkMetadata: linkMetadataForItem(item))
         case .separator(let item):
             SeparatorRoomTimelineView(timelineItem: item)
         case .image(let item):
@@ -64,13 +66,26 @@ struct RoomTimelineItemView: View {
         case .poll(let item):
             PollRoomTimelineView(timelineItem: item)
         case .voice(let item):
-            VoiceMessageRoomTimelineView(timelineItem: item, playerState: context?.viewState.audioPlayerStateProvider?(item.id) ?? AudioPlayerState(id: .timelineItemIdentifier(item.id),
-                                                                                                                                                    title: L10n.commonVoiceMessage,
-                                                                                                                                                    duration: 0))
+            let playerState = context?.viewState.audioPlayerStateProvider?(item.id) ?? AudioPlayerState(id: .timelineItemIdentifier(item.id),
+                                                                                                        title: L10n.commonVoiceMessage,
+                                                                                                        duration: 0)
+            VoiceMessageRoomTimelineView(timelineItem: item, playerState: playerState)
         case .callInvite(let item):
             CallInviteRoomTimelineView(timelineItem: item)
         case .callNotification(let item):
             CallNotificationRoomTimelineView(timelineItem: item)
         }
     }
+    
+    private func linkMetadataForItem(_ item: TextRoomTimelineItem) -> OrderedDictionary<URL, LinkMetadataProviderItem> {
+        var linkMetadata = OrderedDictionary<URL, LinkMetadataProviderItem>()
+        for url in item.links.prefix(TextRoomTimelineView.maxLinkPreviewsToRender) {
+            if let item = context?.viewState.linkMetadataProvider?.metadataItems[url] {
+                linkMetadata[url] = item
+            } else {
+                linkMetadata[url] = LinkMetadataProviderItem(url: url, metadata: nil)
+            }
+        }
+        return linkMetadata
+    }
 }