Reader Mode

App/Reader View/ReaderViewController.swift

@@ -0,0 +1,102 @@
+//
+//  ReaderViewController.swift
+//  App
+//
+//  Created by James Magahern on 2/15/21.
+//
+
+import UIKit
+import WebKit
+
+protocol ReaderViewControllerDelegate: AnyObject
+{
+    func readerViewController(_ reader: ReaderViewController, didRequestNavigationToURL navigationURL: URL)
+}
+
+class ReaderViewController: UIViewController
+{
+    public let baseURL: URL?
+    public let readableHTMLString: String
+    public var darkModeEnabled: Bool = false { didSet { bridge.darkModeEnabled = darkModeEnabled; updateDarkModeButton() } }
+    
+    public weak var delegate: ReaderViewControllerDelegate?
+    
+    private let bridge = ProcessBundleBridge(webViewConfiguration: nil)
+    
+    private let darkModeDisabledImage = UIImage(systemName: "moon.circle")
+    private let darkModeEnabledImage = UIImage(systemName: "moon.circle.fill")
+    
+    private lazy var darkModeButton: UIBarButtonItem = {
+        UIBarButtonItem(image: darkModeEnabledImage, style: .plain, target: self, action: #selector(self.didTapDarkModeButton))
+    }()
+    
+    init(readableHTMLString: String, baseURL: URL?) {
+        self.readableHTMLString = readableHTMLString
+        self.baseURL = baseURL
+        super.init(nibName: nil, bundle: nil)
+    }
+    
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+    
+    override func loadView() {
+        self.view = bridge.webView
+        bridge.webView.navigationDelegate = self
+    }
+    
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        
+        navigationItem.leftBarButtonItem = darkModeButton
+        navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(self.didTapDoneButton))
+    }
+    
+    private func updateDarkModeButton() {
+        if darkModeEnabled {
+            darkModeButton.image = darkModeEnabledImage
+        } else {
+            darkModeButton.image = darkModeDisabledImage
+        }
+    }
+    
+    @objc
+    private func didTapDoneButton(_ sender: Any?) {
+        dismiss(animated: true, completion: nil)
+    }
+    
+    @objc
+    private func didTapDarkModeButton(_ sender: Any?) {
+        darkModeEnabled = !darkModeEnabled
+    }
+    
+    override func viewWillAppear(_ animated: Bool) {
+        let readerHTMLURL = Bundle.main.url(forResource: "reader", withExtension: "html")!
+        var readerHTML = try! String(contentsOf: readerHTMLURL)
+        
+        let bodyRange = readerHTML.range(of: "{{ body }}")!
+        readerHTML.replaceSubrange(bodyRange, with: readableHTMLString)
+        
+        bridge.webView.loadHTMLString(readerHTML, baseURL: baseURL)
+        
+        updateDarkModeButton()
+    }
+}
+
+extension ReaderViewController: WKNavigationDelegate
+{
+    func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
+        guard let url = navigationAction.request.url else { return }
+        
+        if url == baseURL {
+            decisionHandler(.allow)
+            return
+        } else  {
+            // Don't load links in here, dismiss the reader view and load them in the tab behind us. 
+            delegate?.readerViewController(self, didRequestNavigationToURL: url)
+            
+            dismiss(animated: true, completion: nil)
+            decisionHandler(.cancel)
+        }
+    }
+}