Do avatar placeholder in SwiftUI, Add AvatarViewModel, Add dependency injection for MxMediaManager dependency.

Riot/Modules/Common/Avatar/ViewModel/AvatarService.swift

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+//
+// Copyright 2021 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 Foundation
+import MatrixSDK
+import Combine
+import DesignKit
+
+/**
+ Provides a simple api to retrieve and cache avatar images
+ */
+protocol AvatarServiceType {
+    @available(iOS 14.0, *)
+    func avatarImage(mxContentUri: String, avatarSize: AvatarSize) -> Future<UIImage, Error>
+}
+
+enum AvatarServiceError: Error {
+    case pathNotfound
+    case loadingImageFailed(Error?)
+}
+
+class AvatarService: AvatarServiceType {
+    
+    private enum Constants {
+        static let mimeType = "image/jpeg"
+        static let thumbnailMethod = MXThumbnailingMethodCrop
+    }
+    
+    private let mediaManager: MXMediaManager
+    
+    init(mediaManager: MXMediaManager) {
+        self.mediaManager = mediaManager
+    }
+    
+    /**
+     Given an mxContentUri, this function returns a future of UIImage.
+     If possible to retrieve the actual image it will from network or cache, otherwise it will error.
+     
+    - Parameter mxContentUri: matrix uri of the avatar to fetch
+    - Returns: A Future of UIImage that returns an error if it fails to fetch the image
+     */
+    @available(iOS 14.0, *)
+    func avatarImage(mxContentUri: String, avatarSize: AvatarSize) -> Future<UIImage, Error> {
+        
+        let cachePath = MXMediaManager.thumbnailCachePath(
+            forMatrixContentURI: mxContentUri,
+            andType: Constants.mimeType,
+            inFolder: nil, 
+            toFitViewSize: avatarSize.size,
+            with: Constants.thumbnailMethod)
+        
+        return Future<UIImage, Error> { promise in
+            if let image = MXMediaManager.loadThroughCache(withFilePath: cachePath),
+               let imageUp = Self.orientImageUp(image: image) {
+                // Already cached return avatar
+                promise(.success(imageUp))
+            }
+        
+            self.mediaManager.downloadThumbnail(
+                fromMatrixContentURI: mxContentUri,
+                withType: Constants.mimeType,
+                inFolder: nil,
+                toFitViewSize: avatarSize.size,
+                with: Constants.thumbnailMethod) { path in
+                guard let path = path else {
+                    promise(.failure(AvatarServiceError.pathNotfound))
+                    return
+                }
+                
+                guard let image = MXMediaManager.loadThroughCache(withFilePath: path),
+                      let imageUp = Self.orientImageUp(image: image) else {
+                    promise(.failure(AvatarServiceError.loadingImageFailed(nil)))
+                    return
+                }
+                promise(.success(imageUp))
+            } failure: { error in
+                promise(.failure(AvatarServiceError.loadingImageFailed(error)))
+            }
+        }
+    }
+    
+    private static func orientImageUp(image: UIImage) -> UIImage? {
+        guard let image = image.cgImage else { return nil }
+        return UIImage(cgImage: image, scale: 1.0, orientation: .up)
+    }
+}

Riot/Modules/Common/Avatar/ViewModel/AvatarViewModel.swift

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+// 
+// Copyright 2021 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 Foundation
+import Combine
+import DesignKit
+
+@available(iOS 14.0, *)
+class AvatarViewModel: ObservableObject, Injectable {
+    
+    var dependencies: DependencyContainer!
+    
+    @Inject var avatarService: AvatarServiceType
+    
+    @Published private(set) var viewState = AvatarViewState()
+    
+    private var cancellables = Set<AnyCancellable>()
+    
+    func loadAvatar(mxContentUri: String?, avatarSize: AvatarSize) {
+        guard let mxContentUri = mxContentUri else { return }
+        avatarService.avatarImage(mxContentUri: mxContentUri, avatarSize: avatarSize)
+            .sink { error in
+                MXLog.error("[AvatarService] Failed to retrieve avatar.")
+                // TODO: Report non-fatal error when we have Sentry or similar.
+            } receiveValue: { image in
+                self.viewState.avatarImage = image
+            }
+            .store(in: &cancellables)
+    }
+    
+}

Riot/Modules/Common/Avatar/ViewModel/AvatarViewState.swift

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+// 
+// Copyright 2021 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 Foundation
+
+struct AvatarViewState {
+    var avatarImage: UIImage?
+}