/*

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

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    Application Album View.

*/

import UIKit

import Photos

/**

        This UICollectionViewController displayes all albums from

        the Photos library.

 */

class AlbumCollectionViewController: UICollectionViewController {

    // MARK: Properties

    let lightboxSegueName = "LightboxSegue"

    /// Array of albums displayed in this UICollectionView

    var albums = [PHAssetCollection]()

    /// Requests all album and smart albums collections to be fetched.

    override func viewDidLoad() {

        super.viewDidLoad()

        PHPhotoLibrary.requestAuthorization { status in

            guard status == .authorized else { return }

            // Fetch all albums

            PHAssetCollection.fetchAssetCollections(with: PHAssetCollectionType.album, subtype: PHAssetCollectionSubtype.any, options: nil).enumerateObjects( {

                (item, idx, flag) in self.albums.append(item)

            })

            // Fetch all smart albums

            PHAssetCollection.fetchAssetCollections(with: PHAssetCollectionType.smartAlbum, subtype: PHAssetCollectionSubtype.any, options: nil).enumerateObjects({

                (item, idx, flag) in self.albums.append(item)

            })

            OperationQueue.main.addOperation {

                // Ask the collection view to reload data, so the fetched albums is displayed.

                self.collectionView?.reloadData()

            }

        }

    }

    // MARK: UICollectionViewController delegate methods

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

        return albums.count

    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: AlbumCollectionViewCell.reuseIdentifier, for: indexPath) as? AlbumCollectionViewCell else { fatalError("Unable to dequeue an AlbumCollectionViewCell") }

        let collection = albums[indexPath.row]

        cell.imageView.image = nil

        cell.label.text = collection.localizedTitle

        if let firstAsset = PHAsset.fetchAssets(in: collection, options: PHFetchOptions()).firstObject {

            let options = PHImageRequestOptions()

            options.isSynchronous = true

            PHCachingImageManager.default().requestImage(for: firstAsset, targetSize: cell.bounds.size, contentMode: PHImageContentMode.aspectFit, options: options) {

                requestedImage, _ in cell.imageView.image = requestedImage

            }

        }

        return cell

    }

    // MARK: Storyboard seque

    override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

        performSegue(withIdentifier: lightboxSegueName, sender: albums[indexPath[1]])

    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        guard let lightboxController = segue.destination as? LightboxCollectionViewController else { return }

        guard let collection = sender as? PHAssetCollection else { return }

        // Tell the Lightbox what collection do display 

        lightboxController.assetCollection = collection

    }

}