Implemented find on page UI

App/Find on Page/FindOnPageViewController.swift

@@ -0,0 +1,98 @@
+//
+//  FindOnPageViewController.swift
+//  App
+//
+//  Created by James Magahern on 9/30/20.
+//
+
+import UIKit
+
+class FindOnPageViewController: UIViewController, _WKFindDelegate
+{
+    let findOnPageView = FindOnPageView()
+    weak var webView: WKWebView? {
+        didSet { webView?._findDelegate = self }
+    }
+    
+    private var findString: String?
+    private let findOptions: _WKFindOptions = [
+        .caseInsensitive,
+        .atWordStarts,
+        .treatMedialCapitalAsWordStart,
+        .wrapAround,
+        .showFindIndicator,
+        .showOverlay,
+        .showHighlight,
+        .determineMatchIndex,
+    ]
+    
+    private let maxCount: UInt = 1000
+    
+    convenience init() {
+        self.init(nibName: nil, bundle: nil)
+        
+        findOnPageView.textField.addAction(UIAction(handler: { [unowned self] _ in
+            self.findString = findOnPageView.textField.text
+            webView?._find(self.findString, options: self.findOptions, maxCount: self.maxCount)
+        }), for: .editingChanged)
+        
+        findOnPageView.prevResultButton.addAction(UIAction(handler: { [unowned self] _ in
+            findPrevious(nil)
+        }), for: .touchUpInside)
+        
+        findOnPageView.nextResultButton.addAction(UIAction(handler: { [unowned self] _ in
+            findNext(nil)
+        }), for: .touchUpInside)
+        
+        findOnPageView.doneButton.addAction(UIAction(handler: { [unowned self] _ in
+            doneFinding(nil)
+        }), for: .touchUpInside)
+        
+        // Escape to cancel
+        addKeyCommand(UIKeyCommand(input: UIKeyCommand.inputEscape, modifierFlags: [], action: #selector(Self.doneFinding)))
+        
+        // Return goes to next
+        addKeyCommand(UIKeyCommand(input: "\n", modifierFlags: [], action: #selector(Self.findNext)))
+        
+        // Cmd+G next
+        addKeyCommand(UIKeyCommand(input: "G", modifierFlags: [.command], action: #selector(Self.findNext)))
+        
+        // Shift return goes to prev
+        addKeyCommand(UIKeyCommand(input: "\n", modifierFlags: [.shift], action: #selector(Self.findPrevious)))
+        
+        // Shift+Cmd+G prev
+        addKeyCommand(UIKeyCommand(input: "G", modifierFlags: [.command, .shift], action: #selector(Self.findPrevious)))
+        
+        self.view = findOnPageView
+    }
+    
+    @objc
+    func doneFinding(_ sender: Any?) {
+        findOnPageView.textField.resignFirstResponder()
+        webView?._hideFindUI()
+    }
+    
+    @objc
+    func findNext(_ sender: Any?) {
+        webView?._find(self.findString, options: self.findOptions, maxCount: self.maxCount)
+    }
+    
+    @objc
+    func findPrevious(_ sender: Any?) {
+        let options: _WKFindOptions = self.findOptions.union(.backwards)
+        webView?._find(self.findString, options: options, maxCount: self.maxCount)
+    }
+    
+    func _webView(_ webView: WKWebView!, didFailToFind string: String!) {
+        // ??
+    }
+    
+    func _webView(_ webView: WKWebView!, didCountMatches matches: UInt, for string: String!) {
+        // TODO: Update a label
+    }
+    
+    func _webView(_ webView: WKWebView!, didFindMatches matches: UInt, for string: String!, withMatch matchIndex: Int) {
+        findOnPageView.nextResultButton.isEnabled = matches > 0
+        findOnPageView.prevResultButton.isEnabled = matches > 0
+    }
+}