element-ios/Riot/Modules/Common/Avatar/ViewModel/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(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)
    }
}