/*

    Copyright (C) 2016 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

                PhotoImport represents the import operation of a Photo. It combines both the PhotoDownload and PhotoFilter operations.

*/

import UIKit

class PhotoImport: NSObject, ProgressReporting {

    // MARK: Properties

    var completionHandler: ((_ image: UIImage?, _ error: NSError?) -> Void)?

    let progress: Progress

    let download: PhotoDownload

    // MARK: Initializers

    init(URL: Foundation.URL) {

        progress = Progress()

        /* 

            This progress's children are weighted: The download takes up 90% 

            and the filter takes the remaining portion.

        */

        progress.totalUnitCount = 10

        download = PhotoDownload(URL: URL)

    }

    func start() {

        /*

            Use explicit composition to add the download's progress to ours,

            taking 9/10 units.

        */

        progress.addChild(download.progress, withPendingUnitCount: 9)

        download.completionHandler = { data, error in

            guard let imageData = data, let image = UIImage(data: imageData as Data) else {

                self.callCompletionHandler(image: nil, error: error)

                return

            }

            /*

                Make self.progress the currentProgress. Since the filteredImage

                supports implicit progress reporting, it will add its progress

                to ours.

            */

            self.progress.becomeCurrent(withPendingUnitCount: 1)

            let filteredImage = PhotoFilter.filteredImage(image)

            self.progress.resignCurrent()

            self.callCompletionHandler(image: filteredImage, error: nil)

        }

        download.start()

    }

    fileprivate func callCompletionHandler(image: UIImage?, error: NSError?) {

        completionHandler?(image, error)

        completionHandler = nil

    }

}