Fix potential crash when deleting list

Tusker.xcodeproj/project.pbxproj

@@ -314,6 +314,7 @@
 		D6F6A54E291EF7E100F496A8 /* EditListSearchFollowingViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6F6A54D291EF7E100F496A8 /* EditListSearchFollowingViewController.swift */; };
 		D6F6A550291F058600F496A8 /* CreateListService.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6F6A54F291F058600F496A8 /* CreateListService.swift */; };
 		D6F6A552291F098700F496A8 /* RenameListService.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6F6A551291F098700F496A8 /* RenameListService.swift */; };
+		D6F6A554291F0D9600F496A8 /* DeleteListService.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6F6A553291F0D9600F496A8 /* DeleteListService.swift */; };
 		D6F953F021251A2900CF0F2B /* MastodonController.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6F953EF21251A2900CF0F2B /* MastodonController.swift */; };
 		D6FF9860255C717400845181 /* AccountSwitchingContainerViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6FF985F255C717400845181 /* AccountSwitchingContainerViewController.swift */; };
 /* End PBXBuildFile section */
@@ -683,6 +684,7 @@
 		D6F6A54D291EF7E100F496A8 /* EditListSearchFollowingViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = EditListSearchFollowingViewController.swift; sourceTree = "<group>"; };
 		D6F6A54F291F058600F496A8 /* CreateListService.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CreateListService.swift; sourceTree = "<group>"; };
 		D6F6A551291F098700F496A8 /* RenameListService.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RenameListService.swift; sourceTree = "<group>"; };
+		D6F6A553291F0D9600F496A8 /* DeleteListService.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DeleteListService.swift; sourceTree = "<group>"; };
 		D6F953EF21251A2900CF0F2B /* MastodonController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MastodonController.swift; sourceTree = "<group>"; };
 		D6FF985F255C717400845181 /* AccountSwitchingContainerViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AccountSwitchingContainerViewController.swift; sourceTree = "<group>"; };
 /* End PBXFileReference section */
@@ -1494,6 +1496,7 @@
 				D621733228F1D5ED004C7DB1 /* ReblogService.swift */,
 				D6F6A54F291F058600F496A8 /* CreateListService.swift */,
 				D6F6A551291F098700F496A8 /* RenameListService.swift */,
+				D6F6A553291F0D9600F496A8 /* DeleteListService.swift */,
 			);
 			path = API;
 			sourceTree = "<group>";
@@ -1994,6 +1997,7 @@
 				D6C1B2082545D1EC00DAAA66 /* StatusCardView.swift in Sources */,
 				D64BC18A23C16487000D0238 /* UnpinStatusActivity.swift in Sources */,
 				D64D8CA92463B494006B0BAA /* MultiThreadDictionary.swift in Sources */,
+				D6F6A554291F0D9600F496A8 /* DeleteListService.swift in Sources */,
 				D68E6F5F253C9B2D001A1B4C /* BaseEmojiLabel.swift in Sources */,
 				D6F0B12B24A3071C001E48C3 /* MainSplitViewController.swift in Sources */,
 				D6AEBB3E2321638100E5038B /* UIActivity+Types.swift in Sources */,

Tusker/API/DeleteListService.swift

@@ -0,0 +1,65 @@
+//
+//  DeleteListService.swift
+//  Tusker
+//
+//  Created by Shadowfacts on 11/11/22.
+//  Copyright © 2022 Shadowfacts. All rights reserved.
+//
+
+import UIKit
+import Pachyderm
+
+@MainActor
+class DeleteListService {
+    private let list: List
+    private let mastodonController: MastodonController
+    private let present: (UIViewController) -> Void
+    
+    init(list: List, mastodonController: MastodonController, present: @escaping (UIViewController) -> Void) {
+        self.list = list
+        self.mastodonController = mastodonController
+        self.present = present
+    }
+
+    @discardableResult
+    func run() async -> Bool {
+        if await presentConfirmationAlert() {
+            await deleteList()
+            return true
+        } else {
+            return false
+        }
+    }
+    
+    private func presentConfirmationAlert() async -> Bool {
+        await withCheckedContinuation { continuation in
+            let titleFormat = NSLocalizedString("Are you sure you want to delete the '%@' list?", comment: "delete list alert title")
+            let title = String(format: titleFormat, list.title)
+            let alert = UIAlertController(title: title, message: nil, preferredStyle: .alert)
+            alert.addAction(UIAlertAction(title: NSLocalizedString("Cancel", comment: "delete list alert cancel button"), style: .cancel, handler: { (_) in
+                continuation.resume(returning: false)
+            }))
+            alert.addAction(UIAlertAction(title: NSLocalizedString("Delete List", comment: "delete list alert confirm button"), style: .destructive, handler: { (_) in
+                continuation.resume(returning: true)
+            }))
+            present(alert)
+        }
+    }
+    
+    private func deleteList() async {
+        do {
+            let request = List.delete(list)
+            _ = try await mastodonController.run(request)
+            NotificationCenter.default.post(name: .listsChanged, object: nil)
+        } catch {
+            let alert = UIAlertController(title: "Error Deleting List", message: error.localizedDescription, preferredStyle: .alert)
+            alert.addAction(UIAlertAction(title: "Cancel", style: .cancel))
+            alert.addAction(UIAlertAction(title: "Retry", style: .default, handler: { _ in
+                Task {
+                    await self.deleteList()
+                }
+            }))
+            present(alert)
+        }
+    }
+}

Tusker/Screens/Explore/ExploreViewController.swift

@@ -274,29 +274,17 @@ class ExploreViewController: UIViewController, UICollectionViewDelegate {
     }
     
     private func deleteList(_ list: List, completion: @escaping (Bool) -> Void) {
-        let titleFormat = NSLocalizedString("Are you sure you want to delete the '%@' list?", comment: "delete list alert title")
+        Task { @MainActor in
-        let title = String(format: titleFormat, list.title)
+            let service = DeleteListService(list: list, mastodonController: mastodonController, present: { self.present($0, animated: true) })
-        let alert = UIAlertController(title: title, message: nil, preferredStyle: .alert)
+            if await service.run() {
-        alert.addAction(UIAlertAction(title: NSLocalizedString("Cancel", comment: "delete list alert cancel button"), style: .cancel, handler: { (_) in
+                var snapshot = dataSource.snapshot()
-            completion(false)
-        }))
-        alert.addAction(UIAlertAction(title: NSLocalizedString("Delete List", comment: "delete list alert confirm button"), style: .destructive, handler: { (_) in
-            
-            let request = List.delete(list)
-            self.mastodonController.run(request) { (response) in
-                guard case .success(_, _) = response else {
-                    fatalError()
-                }
-                
-                var snapshot = self.dataSource.snapshot()
                 snapshot.deleteItems([.list(list)])
-                DispatchQueue.main.async {
+                await dataSource.apply(snapshot)
-                    self.dataSource.apply(snapshot)
                 completion(true)
+            } else {
+                completion(false)
             }
         }
-        }))
-        present(alert, animated: true)
     }
     
     func removeSavedHashtag(_ hashtag: Hashtag) {