material-components_material-components-ios/components/Cards/examples/EditReorderShapedCollectionViewController.swift

// Copyright 2018-present the Material Components for iOS authors. All Rights Reserved.
//
// 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 UIKit

import MaterialComponents.MaterialCards
import MaterialComponents.MaterialShapeLibrary

class ShapedCardCollectionCell: MDCCardCollectionCell {
  override init(frame: CGRect) {
    super.init(frame: frame)
    commonShapedCardCollectionCellInit()
  }

  required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    commonShapedCardCollectionCellInit()
  }

  func commonShapedCardCollectionCellInit() {
    let shapeGenerator = MDCRectangleShapeGenerator()
    shapeGenerator.topLeftCorner = MDCCutCornerTreatment(cut: 20)
    self.shapeGenerator = shapeGenerator
  }
}

class EditReorderShapedCollectionViewController: UIViewController,
  UICollectionViewDelegate,
  UICollectionViewDataSource,
  UICollectionViewDelegateFlowLayout {

  enum ToggleMode: Int {
    case edit = 1, reorder
  }
  
  let collectionView = UICollectionView(frame: .zero,
                                        collectionViewLayout: UICollectionViewFlowLayout())
  var dataSource = [(Int, Bool)]()
  var longPressGesture: UILongPressGestureRecognizer!
  var toggle = ToggleMode.reorder
  var toggleButton: UIButton!

  override func viewDidLoad() {
    super.viewDidLoad()

    collectionView.frame = view.bounds
    collectionView.dataSource = self
    collectionView.delegate = self
    collectionView.backgroundColor = UIColor(white: 0.9, alpha: 1)
    collectionView.alwaysBounceVertical = true;
    collectionView.register(ShapedCardCollectionCell.self, forCellWithReuseIdentifier: "Cell")
    collectionView.translatesAutoresizingMaskIntoConstraints = false
    collectionView.allowsMultipleSelection = true
    view.addSubview(collectionView)

    navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Reorder",
                                                        style: .plain,
                                                        target: self,
                                                        action: #selector(toggleModes))

    if #available(iOS 9.0, *) {
      longPressGesture = UILongPressGestureRecognizer(target: self,
                                                      action: #selector(handleReordering(gesture:)))
      longPressGesture.cancelsTouchesInView = false
      collectionView.addGestureRecognizer(longPressGesture)
    }

    for i in 0..<20 {
      dataSource.append((i, false))
    }

    #if swift(>=3.2)
      if #available(iOS 11, *) {
        let guide = view.safeAreaLayoutGuide
        NSLayoutConstraint.activate([
          collectionView.leftAnchor.constraint(equalTo: guide.leftAnchor),
          collectionView.rightAnchor.constraint(equalTo: guide.rightAnchor),
          collectionView.topAnchor.constraint(equalTo: view.topAnchor),
          collectionView.bottomAnchor.constraint(equalTo: guide.bottomAnchor)])
        collectionView.contentInsetAdjustmentBehavior = .always
      } else {
        preiOS11Constraints()
      }
    #else
      preiOS11Constraints()
    #endif

  }

  func preiOS11Constraints() {
    self.view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|[view]|",
                                                            options: [],
                                                            metrics: nil,
                                                            views: ["view": collectionView]));
    self.view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|[view]|",
                                                            options: [],
                                                            metrics: nil,
                                                            views: ["view": collectionView]));
  }

  func toggleModes() {
    if toggle == .edit {
      toggle = .reorder
      navigationItem.rightBarButtonItem?.title = "Reorder"
    } else if toggle == .reorder {
      toggle = .edit
      navigationItem.rightBarButtonItem?.title = "Edit"
    }
    collectionView.reloadData()
  }

  func collectionView(_ collectionView: UICollectionView,
                      cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell",
                                                  for: indexPath) as! MDCCardCollectionCell
    cell.backgroundColor = .white
    cell.isSelectable = (toggle == .edit)
    return cell
  }

  func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    if toggle == .edit {
      dataSource[indexPath.item].1 = !dataSource[indexPath.item].1
    }
  }

  func numberOfSections(in collectionView: UICollectionView) -> Int {
    return 1
  }

  func collectionView(_ collectionView: UICollectionView,
                      numberOfItemsInSection section: Int) -> Int {
    return dataSource.count
  }

  func collectionView(_ collectionView: UICollectionView,
                      moveItemAt sourceIndexPath: IndexPath,
                      to destinationIndexPath: IndexPath) {
  }

  func collectionView(_ collectionView: UICollectionView,
                      layout collectionViewLayout: UICollectionViewLayout,
                      sizeForItemAt indexPath: IndexPath) -> CGSize {
    let cardSize = (collectionView.bounds.size.width / 3) - 12
    return CGSize(width: cardSize, height: cardSize)
  }

  func collectionView(_ collectionView: UICollectionView,
                      layout collectionViewLayout: UICollectionViewLayout,
                      insetForSectionAt section: Int) -> UIEdgeInsets {
    return UIEdgeInsets(top: 8, left: 8, bottom: 8, right: 8)
  }

  func collectionView(_ collectionView: UICollectionView,
                      layout collectionViewLayout: UICollectionViewLayout,
                      minimumLineSpacingForSectionAt section: Int) -> CGFloat {
    return 8
  }

  func collectionView(_ collectionView: UICollectionView,
                      layout collectionViewLayout: UICollectionViewLayout,
                      minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
    return 8
  }

  func collectionView(_ collectionView: UICollectionView,
                      canMoveItemAt indexPath: IndexPath) -> Bool {
    return toggle == .reorder
  }

  @available(iOS 9.0, *)
  @objc func handleReordering(gesture: UILongPressGestureRecognizer) {
    if toggle == .reorder {
      switch(gesture.state) {
      case .began:
        guard let selectedIndexPath = collectionView.indexPathForItem(at:
          gesture.location(in: collectionView)) else {
            break
        }
        collectionView.beginInteractiveMovementForItem(at: selectedIndexPath)
      case .changed:
        collectionView.updateInteractiveMovementTargetPosition(gesture.location(in: gesture.view!))
      case .ended:
        collectionView.endInteractiveMovement()
      default:
        collectionView.cancelInteractiveMovement()
      }
    }
  }

}

extension EditReorderShapedCollectionViewController {

  class func catalogMetadata() -> [String: Any] {
    return [
      "breadcrumbs": ["Cards", "Shaped Edit/Reorder"],
      "primaryDemo": false,
      "presentable": false,
    ]
  }
}