Autocomplete UI

App/Autocomplete/AutocompleteViewController.swift

@@ -0,0 +1,73 @@
+//
+//  AutocompleteViewController.swift
+//  App
+//
+//  Created by James Magahern on 9/21/20.
+//
+
+import UIKit
+
+protocol AutocompleteViewControllerDelegate: class {
+    func autocompleteController(_: AutocompleteViewController, didSelectHistoryItem: HistoryItem)
+}
+
+class AutocompleteViewController: UIViewController, UICollectionViewDelegate
+{
+    public var historyItems: [HistoryItem] = [] {
+        didSet {
+            var snapshot = dataSource.snapshot()
+            snapshot.deleteAllItems()
+            snapshot.appendSections([ .HistoryItems ])
+            snapshot.appendItems(historyItems, toSection: .HistoryItems)
+            dataSource.apply(snapshot, animatingDifferences: false)
+        }
+    }
+    
+    public weak var delegate: AutocompleteViewControllerDelegate?
+    
+    private enum Section: Int {
+        case HistoryItems
+    }
+    
+    public let collectionView: UICollectionView
+    private let dataSource: UICollectionViewDiffableDataSource<Section, HistoryItem>
+    
+    init() {
+        let listConfiguration = UICollectionLayoutListConfiguration(appearance: .insetGrouped)
+        let listLayout = UICollectionViewCompositionalLayout.list(using: listConfiguration)
+        collectionView = UICollectionView(frame: .zero, collectionViewLayout: listLayout)
+        
+        let cellRegistry = UICollectionView.CellRegistration<UICollectionViewListCell, HistoryItem> { (cell, indexPath, item) in
+            var config = cell.defaultContentConfiguration()
+            config.text = item.title
+            config.secondaryText = item.url.absoluteString
+            cell.contentConfiguration = config
+        }
+        
+        dataSource = UICollectionViewDiffableDataSource<Section, HistoryItem>(collectionView: collectionView, cellProvider:
+        { (collectionView, indexPath, item) -> UICollectionViewCell? in
+            collectionView.dequeueConfiguredReusableCell(using: cellRegistry, for: indexPath, item: item)
+        })
+        
+        super.init(nibName: nil, bundle: nil)
+        
+        collectionView.delegate = self
+        view.backgroundColor = .systemBackground
+    }
+    
+    required init?(coder: NSCoder) { fatalError("init(coder:) has not been implemented") }
+    
+    override func loadView() {
+        self.view = collectionView
+    }
+    
+    // MARK: UICollectionViewDelegate
+    
+    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
+        collectionView.deselectItem(at: indexPath, animated: true)
+        
+        if let item = dataSource.itemIdentifier(for: indexPath) {
+            delegate?.autocompleteController(self, didSelectHistoryItem: item)
+        }
+    }
+}