persephone/Persephone/Components/Browser/Album Browser/AlbumViewController.swift

//
//  AlbumViewController.swift
//  Persephone
//
//  Created by Daniel Barber on 2019/2/08.
//  Copyright © 2019 Dan Barber. All rights reserved.
//

import AppKit
import ReSwift
import Differ

class AlbumViewController: NSViewController,
                           NSCollectionViewDelegateFlowLayout {
  var dataSource = AlbumDataSource()
  let layout = FlexibleGridViewLayout(coder: NSCoder())

  override func viewDidLoad() {
    super.viewDidLoad()

    App.store.subscribe(self) {
      $0.select { $0.albumListState }
    }

    NotificationCenter.default.addObserver(self, selector: #selector(didConnect), name: .didConnect, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(willDisconnect), name: .willDisconnect, object: nil)

    albumScrollView.postsBoundsChangedNotifications = true

    albumCollectionView.dataSource = dataSource
    layout?.extraHeight = 44
    albumCollectionView.collectionViewLayout = layout

    registerForDragAndDrop(albumCollectionView)
  }

  deinit {
    App.store.unsubscribe(self)
  }

  override func viewWillLayout() {
    super.viewWillLayout()

    if let layout = albumCollectionView.collectionViewLayout as? FlexibleGridViewLayout {
      layout.saveScrollPosition()
    }

    albumCollectionView.collectionViewLayout?.invalidateLayout()
  }

  override func viewDidLayout() {
    super.viewDidLayout()

    guard let layout = albumCollectionView.collectionViewLayout as? FlexibleGridViewLayout
      else { return }

    layout.setScrollPosition()
  }

  @objc func didConnect() {
    App.mpdClient.fetchAllAlbums()
  }

  @objc func willDisconnect() {
    DispatchQueue.main.async {
      App.store.dispatch(UpdateAlbumListAction(albums: []))
    }
  }

  @IBOutlet var albumScrollView: NSScrollView!
  @IBOutlet var albumCollectionView: NSCollectionView!
}

extension AlbumViewController: StoreSubscriber {
  typealias StoreSubscriberStateType = AlbumListState

  func newState(state: StoreSubscriberStateType) {
    let oldAlbums = dataSource.albums

    dataSource.albums = state.albums

    albumCollectionView.animateItemChanges(
      oldData: oldAlbums,
      newData: dataSource.albums
    )
  }
}