Automatically try reloading failed images on network changes (#3170)

* Add the networkMonitor to the NSE and delete the old MockMediaLoader

* Generate a MediaLoaderMock through AutoMockable and use it in the MediaProviderTests

* Implement an ImageProvider mechanism that automatically tries reloading images when connectivity is established again and use it for LoadableImages

* Merge the ImageProvider protocol back into the MediaProvider

* Address PR review comments

* Provide a default sdk client request configuration

* Address tasks not automatically cancelling themselves when views get deallocated

ElementX/Sources/Services/Media/Provider/ImageProviderProtocol.swift

@@ -1,31 +0,0 @@
-//
-// Copyright 2023 New Vector Ltd
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-//
-
-import UIKit
-
-protocol ImageProviderProtocol {
-    func imageFromSource(_ source: MediaSourceProxy?, size: CGSize?) -> UIImage?
-    
-    func loadImageFromSource(_ source: MediaSourceProxy, size: CGSize?) async -> Result<UIImage, MediaProviderError>
-    
-    func loadImageDataFromSource(_ source: MediaSourceProxy) async -> Result<Data, MediaProviderError>
-}
-
-extension ImageProviderProtocol {
-    func imageFromSource(_ source: MediaSourceProxy?) -> UIImage? {
-        imageFromSource(source, size: nil)
-    }
-}

ElementX/Sources/Services/Media/Provider/MediaLoaderProtocol.swift

@@ -16,6 +16,7 @@
 
 import Foundation
 
+// sourcery: AutoMockable
 protocol MediaLoaderProtocol {
     func loadMediaContentForSource(_ source: MediaSourceProxy) async throws -> Data
 

ElementX/Sources/Services/Media/Provider/MediaProvider.swift

@@ -14,17 +14,21 @@
 // limitations under the License.
 //
 
+import Combine
 import Kingfisher
 import UIKit
 
 struct MediaProvider: MediaProviderProtocol {
     private let mediaLoader: MediaLoaderProtocol
     private let imageCache: Kingfisher.ImageCache
+    private let networkMonitor: NetworkMonitorProtocol?
     
     init(mediaLoader: MediaLoaderProtocol,
-         imageCache: Kingfisher.ImageCache) {
+         imageCache: Kingfisher.ImageCache,
+         networkMonitor: NetworkMonitorProtocol?) {
         self.mediaLoader = mediaLoader
         self.imageCache = imageCache
+        self.networkMonitor = networkMonitor
     }
     
     // MARK: Images
@@ -71,6 +75,45 @@ struct MediaProvider: MediaProviderProtocol {
         }
     }
     
+    func loadImageRetryingOnReconnection(_ source: MediaSourceProxy, size: CGSize?) -> Task<UIImage, any Error> {
+        guard let networkMonitor else {
+            fatalError("This method shouldn't be invoked without a NetworkMonitor set.")
+        }
+        
+        return Task {
+            if case let .success(image) = await loadImageFromSource(source, size: size) {
+                return image
+            }
+            
+            guard !Task.isCancelled else {
+                throw MediaProviderError.cancelled
+            }
+            
+            for await reachability in networkMonitor.reachabilityPublisher.values {
+                guard !Task.isCancelled else {
+                    throw MediaProviderError.cancelled
+                }
+                
+                guard reachability == .reachable else {
+                    continue
+                }
+                
+                switch await loadImageFromSource(source, size: size) {
+                case .success(let image):
+                    return image
+                case .failure:
+                    // If it fails after a retry with the network available
+                    // then something else must be wrong. Bail out.
+                    if reachability == .reachable {
+                        throw MediaProviderError.cancelled
+                    }
+                }
+            }
+            
+            throw MediaProviderError.cancelled
+        }
+    }
+    
     func loadImageDataFromSource(_ source: MediaSourceProxy) async -> Result<Data, MediaProviderError> {
         do {
             let imageData = try await mediaLoader.loadMediaContentForSource(source)

ElementX/Sources/Services/Media/Provider/MediaProviderProtocol.swift

@@ -22,14 +22,29 @@ enum MediaProviderError: Error {
     case failedRetrievingFile
     case invalidImageData
     case failedRetrievingThumbnail
+    case cancelled
 }
 
-protocol MediaProviderProtocol: ImageProviderProtocol {
-    func loadFileFromSource(_ source: MediaSourceProxy, body: String?) async -> Result<MediaFileHandleProxy, MediaProviderError>
+protocol MediaProviderProtocol {
+    func imageFromSource(_ source: MediaSourceProxy?, size: CGSize?) -> UIImage?
+    func loadImageFromSource(_ source: MediaSourceProxy, size: CGSize?) async -> Result<UIImage, MediaProviderError>
+    func loadImageDataFromSource(_ source: MediaSourceProxy) async -> Result<Data, MediaProviderError>
+    func loadImageRetryingOnReconnection(_ source: MediaSourceProxy, size: CGSize?) -> Task<UIImage, Error>
+    
     func loadThumbnailForSource(source: MediaSourceProxy, size: CGSize) async -> Result<Data, MediaProviderError>
+    
+    func loadFileFromSource(_ source: MediaSourceProxy, body: String?) async -> Result<MediaFileHandleProxy, MediaProviderError>
 }
 
 extension MediaProviderProtocol {
+    func imageFromSource(_ source: MediaSourceProxy?) -> UIImage? {
+        imageFromSource(source, size: nil)
+    }
+    
+    func loadImageRetryingOnReconnection(_ source: MediaSourceProxy) -> Task<UIImage, Error> {
+        loadImageRetryingOnReconnection(source, size: nil)
+    }
+    
     func loadFileFromSource(_ source: MediaSourceProxy) async -> Result<MediaFileHandleProxy, MediaProviderError> {
         await loadFileFromSource(source, body: nil)
     }

ElementX/Sources/Services/Media/Provider/MockMediaProvider.swift

@@ -58,4 +58,14 @@ struct MockMediaProvider: MediaProviderProtocol {
         }
         return .failure(.failedRetrievingFile)
     }
+    
+    func loadImageRetryingOnReconnection(_ source: MediaSourceProxy, size: CGSize?) -> Task<UIImage, any Error> {
+        Task {
+            guard let image = UIImage(systemName: "photo") else {
+                fatalError()
+            }
+            
+            return image
+        }
+    }
 }

ElementX/Sources/Services/UserSession/UserSessionStore.swift

@@ -111,7 +111,8 @@ class UserSessionStore: UserSessionStoreProtocol {
     
     private func buildUserSessionWithClient(_ clientProxy: ClientProxyProtocol) -> UserSessionProtocol {
         let mediaProvider = MediaProvider(mediaLoader: clientProxy,
-                                          imageCache: .onlyInMemory)
+                                          imageCache: .onlyInMemory,
+                                          networkMonitor: networkMonitor)
         
         let voiceMessageMediaManager = VoiceMessageMediaManager(mediaProvider: mediaProvider)