element-ios/Riot/Modules/Common/Avatar/AvatarService.swift

//
// 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(inputData: AvatarInputType) -> AnyPublisher<UIImage?, Never>
}

enum AvatarServiceError: Error {
    case pathNotfound
    case loadingImageFailed(Error?)
}

class AvatarService: AvatarServiceType {
    
    private enum Constants {
        static let mimeType = "image/jpeg"
        static let thumbnailMethod = MXThumbnailingMethodCrop
        static let avatarDownloadSize = AvatarSize.xxLarge.size
    }
    
    let avatarGenerator: AvatarGenerator
    let mediaManager: MXMediaManager
    
    init(avatarGenerator: AvatarGenerator, mediaManager: MXMediaManager) {
        self.avatarGenerator = avatarGenerator
        self.mediaManager = mediaManager
    }
    
    @available(iOS 14.0, *)
    func avatarImage(inputData: AvatarInputType) -> AnyPublisher<UIImage?, Never> {
        
        let generatedAvatar = AvatarGenerator.generateAvatar(forMatrixItem: inputData.itemId, withDisplayName: inputData.displayName)
        guard let mxContentUri = inputData.mxContentUri else {
            // No content URI just complete with the generated avatar
            return Just(generatedAvatar)
                .eraseToAnyPublisher()
        }
        
        let cachePath = MXMediaManager.thumbnailCachePath(
            forMatrixContentURI: mxContentUri,
            andType: Constants.mimeType,
            inFolder: nil, 
            toFitViewSize: Constants.avatarDownloadSize,
            with: Constants.thumbnailMethod)
        
        if let image = MXMediaManager.loadThroughCache(withFilePath: cachePath) {
            // Already cached, complete with the avatar
            return Just(Self.orientImageUp(image: image))
                .eraseToAnyPublisher()
        }
        
        let future = Future<UIImage?, Error> { promise in
            self.mediaManager.downloadThumbnail(
                fromMatrixContentURI: mxContentUri,
                withType: Constants.mimeType,
                inFolder: nil,
                toFitViewSize: Constants.avatarDownloadSize,
                with: Constants.thumbnailMethod) { path in
                guard let path = path else {
                    promise(.failure(AvatarServiceError.pathNotfound))
                    return
                }
                
                let image = MXMediaManager.loadThroughCache(withFilePath: path)
                promise(.success(Self.orientImageUp(image: image)))
            } failure: { error in
                promise(.failure(AvatarServiceError.loadingImageFailed(error)))
            }
        }
        // First publish the generated avatar and then complete with the retrieved one
        // In the case of an error retreiving the avatar also return generated one.
        return future
            .prepend(generatedAvatar)
            .catch { _ -> Just<UIImage?> in
                MXLog.error("[AvatarService] Failed to retrieve avatar.")
                // TODO: Report non-fatal error when we have Sentry or similar.
                return Just(generatedAvatar)
            }
            .eraseToAnyPublisher()
    }
    
    private static func orientImageUp(image: UIImage?) -> UIImage? {
        guard let image = image?.cgImage else { return nil }
        return UIImage(cgImage: image, scale: 1.0, orientation: .up)
    }
}