Add QuickLook fallback for showing unknown attachments in the gallery

Closes #169

Tusker.xcodeproj/project.pbxproj

@@ -304,6 +304,7 @@
 		D6D79F532A0FFE3200AB2315 /* ToggleableButton.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6D79F522A0FFE3200AB2315 /* ToggleableButton.swift */; };
 		D6D79F572A1160B800AB2315 /* AccountDisplayNameLabel.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6D79F562A1160B800AB2315 /* AccountDisplayNameLabel.swift */; };
 		D6D79F592A13293200AB2315 /* BackgroundManager.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6D79F582A13293200AB2315 /* BackgroundManager.swift */; };
+		D6D79F5B2A13D22B00AB2315 /* GalleryFallbackViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6D79F5A2A13D22B00AB2315 /* GalleryFallbackViewController.swift */; };
 		D6D94955298963A900C59229 /* Colors.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6D94954298963A900C59229 /* Colors.swift */; };
 		D6D9498D298CBB4000C59229 /* TrendingStatusCollectionViewCell.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6D9498C298CBB4000C59229 /* TrendingStatusCollectionViewCell.swift */; };
 		D6D9498F298EB79400C59229 /* CopyableLable.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6D9498E298EB79400C59229 /* CopyableLable.swift */; };
@@ -706,6 +707,7 @@
 		D6D79F522A0FFE3200AB2315 /* ToggleableButton.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ToggleableButton.swift; sourceTree = "<group>"; };
 		D6D79F562A1160B800AB2315 /* AccountDisplayNameLabel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AccountDisplayNameLabel.swift; sourceTree = "<group>"; };
 		D6D79F582A13293200AB2315 /* BackgroundManager.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = BackgroundManager.swift; sourceTree = "<group>"; };
+		D6D79F5A2A13D22B00AB2315 /* GalleryFallbackViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GalleryFallbackViewController.swift; sourceTree = "<group>"; };
 		D6D94954298963A900C59229 /* Colors.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Colors.swift; sourceTree = "<group>"; };
 		D6D9498C298CBB4000C59229 /* TrendingStatusCollectionViewCell.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TrendingStatusCollectionViewCell.swift; sourceTree = "<group>"; };
 		D6D9498E298EB79400C59229 /* CopyableLable.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CopyableLable.swift; sourceTree = "<group>"; };
@@ -1092,6 +1094,7 @@
 				D6C94D862139E62700CB5196 /* LargeImageViewController.swift */,
 				D681A299249AD62D0085E54E /* LargeImageContentView.swift */,
 				041160FE22B442870030A9B7 /* LoadingLargeImageViewController.swift */,
+				D6D79F5A2A13D22B00AB2315 /* GalleryFallbackViewController.swift */,
 			);
 			path = "Large Image";
 			sourceTree = "<group>";
@@ -2148,6 +2151,7 @@
 				D6E77D0B286D426E00D8B732 /* TrendingLinkCardCollectionViewCell.swift in Sources */,
 				D6114E1127F899B30080E273 /* TrendingLinksViewController.swift in Sources */,
 				D65B4B58297203A700DABDFB /* ReportSelectRulesView.swift in Sources */,
+				D6D79F5B2A13D22B00AB2315 /* GalleryFallbackViewController.swift in Sources */,
 				D6C3F4FB299035650009FCFF /* TrendsViewController.swift in Sources */,
 				D6B81F442560390300F6E31D /* MenuController.swift in Sources */,
 				D691771129A2B76A0054D7EF /* MainActor+Unsafe.swift in Sources */,

Tusker/Screens/Attachment Gallery/GalleryViewController.swift

@@ -109,7 +109,7 @@ class GalleryViewController: UIPageViewController, UIPageViewControllerDataSourc
                 vc.shrinkGestureEnabled = false
                 return vc
             default:
-                fatalError()
+                return UINavigationController(rootViewController: GalleryFallbackViewController(attachment: attachment))
             }
         }
         

Tusker/Screens/Large Image/GalleryFallbackViewController.swift

@@ -0,0 +1,71 @@
+//
+//  GalleryFallbackViewController.swift
+//  Tusker
+//
+//  Created by Shadowfacts on 5/16/23.
+//  Copyright © 2023 Shadowfacts. All rights reserved.
+//
+
+import UIKit
+import QuickLook
+import Pachyderm
+
+class GalleryFallbackViewController: QLPreviewController {
+    
+    private let attachment: Attachment
+    private let previewItem: GalleryPreviewItem
+    
+    private var loadAttachmentTask: Task<Void, Never>?
+    
+    deinit {
+        loadAttachmentTask?.cancel()
+    }
+    
+    init(attachment: Attachment) {
+        self.attachment = attachment
+        self.previewItem = GalleryPreviewItem()
+        
+        super.init(nibName: nil, bundle: nil)
+        
+        dataSource = self
+    }
+    
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+    
+    override func viewWillAppear(_ animated: Bool) {
+        super.viewWillAppear(animated)
+        
+        if previewItem.previewItemURL == nil,
+           loadAttachmentTask == nil {
+            loadAttachmentTask = Task {
+                do {
+                    let (data, _) = try await URLSession.shared.data(from: attachment.url)
+                    let url = FileManager.default.temporaryDirectory.appendingPathComponent(attachment.url.lastPathComponent)
+                    try data.write(to: url)
+                    try Task.checkCancellation()
+                    previewItem.previewItemURL = url
+                    refreshCurrentPreviewItem()
+                } catch {
+                    return
+                }
+            }
+        }
+    }
+    
+}
+
+extension GalleryFallbackViewController: QLPreviewControllerDataSource {
+    func numberOfPreviewItems(in controller: QLPreviewController) -> Int {
+        return 1
+    }
+    
+    func previewController(_ controller: QLPreviewController, previewItemAt index: Int) -> QLPreviewItem {
+        return previewItem
+    }
+}
+
+private class GalleryPreviewItem: NSObject, QLPreviewItem {
+    var previewItemURL: URL? = nil
+}