Add own-instance API request retrying

Tusker/Controllers/MastodonController.swift

@@ -46,6 +46,9 @@ class MastodonController: ObservableObject {
     @Published private(set) var instance: Instance!
     private(set) var customEmojis: [Emoji]?
     
+    private var pendingOwnInstanceRequestCallbacks = [(Instance) -> Void]()
+    private var ownInstanceRequest: URLSessionTask?
+    
     var loggedIn: Bool {
         accountInfo != nil
     }
@@ -115,17 +118,56 @@ class MastodonController: ObservableObject {
         }
     }
     
-    // todo: this should dedup requests
     func getOwnInstance(completion: ((Instance) -> Void)? = nil) {
+        getOwnInstanceInternal(retryAttempt: 0, completion: completion)
+    }
+    
+    private func getOwnInstanceInternal(retryAttempt: Int, completion: ((Instance) -> Void)?) {
+        // this is main thread only to prevent concurrent access to ownInstanceRequest and pendingOwnInstanceRequestCallbacks
+        assert(Thread.isMainThread)
+        
         if let instance = self.instance {
             completion?(instance)
         } else {
-            let request = Client.getInstance()
-            run(request) { (response) in
-                guard case let .success(instance, _) = response else { fatalError() }
-                DispatchQueue.main.async {
-                    self.instance = instance
-                    completion?(instance)
+            if let completion = completion {
+                pendingOwnInstanceRequestCallbacks.append(completion)
+            }
+          
+            if ownInstanceRequest == nil {
+                let request = Client.getInstance()
+                ownInstanceRequest = run(request) { (response) in
+                    switch response {
+                    case .failure(_):
+                        let delay: DispatchTimeInterval
+                        switch retryAttempt {
+                        case 0:
+                            delay = .seconds(1)
+                        case 1:
+                            delay = .seconds(5)
+                        case 2:
+                            delay = .seconds(30)
+                        case 3:
+                            delay = .seconds(60)
+                        default:
+                            // if we've failed four times, just give up :/
+                            return
+                        }
+                        DispatchQueue.main.asyncAfter(deadline: .now() + delay) {
+                            // completion is nil because in this invocation of getOwnInstanceInternal we've already added it to the pending callbacks array
+                            self.getOwnInstanceInternal(retryAttempt: retryAttempt + 1, completion: nil)
+                        }
+
+                    case let .success(instance, _):
+                        DispatchQueue.main.async {
+                            self.ownInstanceRequest = nil
+                            self.instance = instance
+                            
+                            for completion in self.pendingOwnInstanceRequestCallbacks {
+                                completion(instance)
+                            }
+                            self.pendingOwnInstanceRequestCallbacks = []
+                        }
+                    }
                 }
             }
         }

Tusker/Screens/Asset Picker/AssetCollectionViewController.swift

@@ -69,6 +69,7 @@ class AssetCollectionViewController: UICollectionViewController {
         navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(donePressed))
 
         collectionView.alwaysBounceVertical = true
+        collectionView.allowsMultipleSelection = true
         
         collectionView.register(UINib(nibName: "AssetCollectionViewCell", bundle: .main), forCellWithReuseIdentifier: reuseIdentifier)
         collectionView.register(UINib(nibName: "ShowCameraCollectionViewCell", bundle: .main), forCellWithReuseIdentifier: cameraReuseIdentifier)
@@ -97,19 +98,6 @@ class AssetCollectionViewController: UICollectionViewController {
             }
         })
         
-        let options = PHFetchOptions()
-        options.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
-        fetchResult = fetchAssets(with: options)
-        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
-        snapshot.appendSections([.assets])
-        var items: [Item] = [.showCamera]
-        fetchResult.enumerateObjects { (asset, _, _) in
-            items.append(.asset(asset))
-        }
-        snapshot.appendItems(items)
-        dataSource.apply(snapshot, animatingDifferences: false)
-        
-        collectionView.allowsMultipleSelection = true
         setEditing(true, animated: false)
         
         updateItemsSelectedCount()
@@ -122,6 +110,12 @@ class AssetCollectionViewController: UICollectionViewController {
         }
     }
     
+    override func viewWillAppear(_ animated: Bool) {
+        super.viewWillAppear(animated)
+        
+        loadAssets()
+    }
+    
     override func viewWillLayoutSubviews() {
         super.viewWillLayoutSubviews()
         
@@ -137,6 +131,40 @@ class AssetCollectionViewController: UICollectionViewController {
         }
     }
     
+    private func loadAssets() {
+        switch PHPhotoLibrary.authorizationStatus(for: .readWrite) {
+        case .notDetermined:
+            PHPhotoLibrary.requestAuthorization(for: .readWrite) { (_) in
+                self.loadAssets()
+            }
+            return
+            
+        case .restricted, .denied:
+            // todo: better UI for this
+            return
+            
+        case .authorized, .limited:
+            // todo: show "add more" button for limited access
+            break
+            
+        @unknown default:
+            // who knows, just try anyways
+            break
+        }
+        
+        let options = PHFetchOptions()
+        options.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
+        fetchResult = fetchAssets(with: options)
+        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
+        snapshot.appendSections([.assets])
+        var items: [Item] = [.showCamera]
+        fetchResult.enumerateObjects { (asset, _, _) in
+            items.append(.asset(asset))
+        }
+        snapshot.appendItems(items)
+        dataSource.apply(snapshot, animatingDifferences: false)
+    }
+    
     open func fetchAssets(with options: PHFetchOptions) -> PHFetchResult<PHAsset> {
         return PHAsset.fetchAssets(with: options)
     }

Tusker/Screens/Explore/ProfileDirectoryFilterView.swift

@@ -118,7 +118,7 @@ class ProfileDirectoryFilterView: UICollectionReusableView {
     }
     
     @objc private func filterChanged() {
-        let scope = Scope(rawValue: scope.selectedSegmentIndex)!
+        let scope = Scope(rawValue: self.scope.selectedSegmentIndex)!
         let order = sort.selectedSegmentIndex == 0 ? DirectoryOrder.active : .new
         onFilterChanged?(scope, order)
     }

Tusker/Screens/Large Image/LoadingLargeImageViewController.swift

@@ -94,11 +94,11 @@ class LoadingLargeImageViewController: UIViewController, LargeImageAnimatableVie
             loadingVC = LoadingViewController()
             embedChild(loadingVC!)
             imageRequest = cache.get(url, loadOriginal: true) { [weak self] (data, image) in
-                guard let self = self else { return }
+                guard let self = self, let image = image else { return }
                 self.imageRequest = nil
                 DispatchQueue.main.async {
                     self.loadingVC?.removeViewAndController()
-                    self.createLargeImage(data: data!, image: image!, url: self.url)
+                    self.createLargeImage(data: data, image: image, url: self.url)
                 }
             }
         }

Tusker/Screens/Timeline/TimelineTableViewController.swift

@@ -72,7 +72,10 @@ class TimelineTableViewController: TimelineLikeTableViewController<TimelineEntry
         let request = Client.getStatuses(timeline: timeline)
         
         mastodonController?.run(request) { (response) in
-            guard case let .success(statuses, pagination) = response else { fatalError() }
+            guard case let .success(statuses, pagination) = response else {
+                completion([])
+                return
+            }
             
             self.newer = pagination?.newer
             self.older = pagination?.older
@@ -92,7 +95,10 @@ class TimelineTableViewController: TimelineLikeTableViewController<TimelineEntry
         let request = Client.getStatuses(timeline: timeline, range: older)
         
         mastodonController.run(request) { (response) in
-            guard case let .success(statuses, pagination) = response else { fatalError() }
+            guard case let .success(statuses, pagination) = response else {
+                completion([])
+                return
+            }
             
             self.older = pagination?.older
             
@@ -111,7 +117,10 @@ class TimelineTableViewController: TimelineLikeTableViewController<TimelineEntry
         let request = Client.getStatuses(timeline: timeline, range: newer)
         
         mastodonController.run(request) { (response) in
-            guard case let .success(statuses, pagination) = response else { fatalError() }
+            guard case let .success(statuses, pagination) = response else {
+                completion([])
+                return
+            }
             
             // if there are no new statuses, pagination is nil
             // if we were to then overwrite self.newer, future refreshes would fail

Tusker/Screens/Utilities/TimelineLikeTableViewController.swift

@@ -65,11 +65,18 @@ class TimelineLikeTableViewController<Item>: EnhancedTableViewController, Refres
     
     func loadInitial() {
         guard !loaded else { return }
+        // set loaded immediately so we don't trigger another request while the current one is running
         loaded = true
         
         loadInitialItems() { (items) in
-            guard items.count > 0 else { return }
             DispatchQueue.main.async {
+                guard items.count > 0 else {
+                    // set loaded back to false so the next time the VC appears, we try to load again
+                    // todo: this should probably retry automatically
+                    self.loaded = false
+                    return
+                }
+                
                 if self.sections.count < self.headerSectionsCount() {
                     self.sections.insert(contentsOf: Array(repeating: [], count: self.headerSectionsCount() - self.sections.count), at: 0)
                 }
@@ -97,6 +104,8 @@ class TimelineLikeTableViewController<Item>: EnhancedTableViewController, Refres
         return "Refresh"
     }
     
+    // todo: these three should use Result<[Item], Client.Error> so we can differentiate between failed requests and there actually being no results
+    
     func loadInitialItems(completion: @escaping ([Item]) -> Void) {
         fatalError("loadInitialItems(completion:) must be implemented by subclasses")
     }