//
  //  SingleImageSavingInteractor.swift
  //  ALCameraViewController
  //
  //  Created by Alex Littlejohn on 2016/02/16.
  //  Copyright © 2016 zero. All rights reserved.
  //
  
  import UIKit
  import Photos
  
  public typealias SingleImageSaverSuccess = (PHAsset) -> Void
  public typealias SingleImageSaverFailure = (NSError) -> Void
  
  public class SingleImageSaver {
      private let errorDomain = "com.zero.singleImageSaver"
      
      private var success: SingleImageSaverSuccess?
      private var failure: SingleImageSaverFailure?
      
      private var image: UIImage?
      
      public init() { }
      
      public func onSuccess(_ success: @escaping SingleImageSaverSuccess) -> Self {
          self.success = success
          return self
      }
      
      public func onFailure(_ failure: @escaping SingleImageSaverFailure) -> Self {
          self.failure = failure
          return self
      }
      
      public func setImage(_ image: UIImage) -> Self {
          self.image = image
          return self
      }
      
      public func save() -> Self {
          
          _ = PhotoLibraryAuthorizer { error in
              if error == nil {
                  self._save()
              } else {
                  self.failure?(error!)
              }
          }
  
          return self
      }
      
      private func _save() {
          guard let image = image else {
              self.invokeFailure()
              return
          }
          
          var assetIdentifier: PHObjectPlaceholder?
          
          PHPhotoLibrary.shared()
              .performChanges({
                  let request = PHAssetChangeRequest.creationRequestForAsset(from: image)
                  assetIdentifier = request.placeholderForCreatedAsset
              }) { finished, error in
                  
                  guard let assetIdentifier = assetIdentifier, finished else {
                      self.invokeFailure()
                      return
                  }
                  
                  self.fetch(assetIdentifier)
          }
      }
      
      private func fetch(_ assetIdentifier: PHObjectPlaceholder) {
          
          let assets = PHAsset.fetchAssets(withLocalIdentifiers: [assetIdentifier.localIdentifier], options: nil)
          
          DispatchQueue.main.async {
              guard let asset = assets.firstObject else {
                  self.invokeFailure()
                  return
              }
              
              self.success?(asset)
          }
      }
      
      private func invokeFailure() {
          let error = errorWithKey("error.cant-fetch-photo", domain: errorDomain)
          failure?(error)
      }
  }