LeeKahSeng/hijack-webview-nav-full.swift

## hijack-webview-nav-full.swift
import UIKit
import WebKit

// MARK: - Code related to "How to Hijack WKWebView Navigation Actions" starts here.
// https://swiftsenpai.com/development/hijack-wkwebview-navigation/

class ColorViewController: UIViewController {

    var screenColor: UIColor?

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = screenColor
    }
}

enum TransitionType: String {
    case present
    case push
}

enum ActionType: String {
    case navigate
}

extension HijackViewController: WKNavigationDelegate {

    func webView(_ webView: WKWebView,
                 decidePolicyFor navigationAction: WKNavigationAction,
                 decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {

        if
            navigationAction.navigationType == WKNavigationType.linkActivated,
            let url = navigationAction.request.url {

            // Check is user request to perform custom navigate action
            if
                let scheme = url.scheme,
                let actionType = ActionType(rawValue: scheme),
                actionType == .navigate {

                // Extract transition type from URL
                guard
                    let host = url.host,
                    let transitionType = TransitionType(rawValue: host) else {
                        return
                    }

                // Extract RGB from URL query items
                guard
                    let component = URLComponents(string: url.absoluteString),
                    let r = component.queryItems?.first(where: { $0.name == "r" })?.value,
                    let g = component.queryItems?.first(where: { $0.name == "g" })?.value,
                    let b = component.queryItems?.first(where: { $0.name == "b" })?.value else {
                        return
                    }

                // Convert rgb String to Double (Only available in Swift 5.5)
                guard
                    let red = Double(r),
                    let green = Double(g),
                    let blue = Double(b) else {
                        return
                    }

                let viewController = ColorViewController()
                let screenColor = UIColor(red: red, green: green, blue: blue, alpha: 1.0)
                viewController.screenColor = screenColor

                // Perform navigation based on transition type
                switch transitionType {
                case .present:
                    present(viewController, animated: true)
                case .push:
                    navigationController?.pushViewController(viewController, animated: true)
                }

            } else {
                // Load URL as usual
                let req = URLRequest(url: url)
                webView.load(req)
            }

            decisionHandler(.cancel)
            return
        }

        decisionHandler(.allow)
    }
}

// MARK: - Following code showcases JavaScript injection technique discussed in "Injecting JavaScript Into Web View In iOS".
// https://swiftsenpai.com/development/web-view-javascript-injection/
class HijackViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        configureWebView()
    }

    private func configureWebView() {

        let css = """
        html, body {
          overflow-x: hidden;
        }

        body {
          background-color: #333333;
          line-height: 1.5;
          color: white;
          padding: 10;
          font-weight: 600;
          font-family: -apple-system;
        }

        a {
          color: white;
        }
        """

        // Make CSS into single liner
        let cssString = css.components(separatedBy: .newlines).joined()

        // Create JavaScript that loads the CSS
        let javaScript = """
           var element = document.createElement('style');
           element.innerHTML = '\(cssString)';
           document.head.appendChild(element);
        """

        // Create user script that inject the JavaScript after the HTML finishes loading
        let userScript = WKUserScript(source: javaScript,
                                      injectionTime: .atDocumentEnd,
                                      forMainFrameOnly: true)

        // Set user script to a configuration object and load it into the webView
        let userContentController = WKUserContentController()
        userContentController.addUserScript(userScript)
        let configuration = WKWebViewConfiguration()
        configuration.userContentController = userContentController
        let webView = WKWebView(frame: CGRect.zero, configuration: configuration)

        // Show web view on screen
        view.addSubview(webView)
        webView.layer.cornerRadius = 20.0
        webView.layer.masksToBounds = true
        webView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            webView.topAnchor.constraint(equalTo: view.layoutMarginsGuide.topAnchor, constant: 20.0),
            webView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20.0),
            webView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20.0),
            webView.bottomAnchor.constraint(equalTo: view.layoutMarginsGuide.bottomAnchor, constant: -20.0),
        ])

        webView.navigationDelegate = self

        // Load content to webView
        let htmlContent =
                        """
                        <h1>Swift Senpai Demo</h1>
                        <h2>This is a web view</h2>

                        <ul>
                            <li><a href="navigate://present?r=255&g=255&b=0" target="_blank">Present Yellow Screen</a></li>
                            <li><a href="navigate://push?r=255&g=0&b=0" target="_blank">Push Red Screen</a></li>
                        </ul>
                        """

        // Prepend `<meta>` viewport element to the HTML so that it will scale correctly in a mobile device
        let metaTag = "<meta name=\"viewport\" content=\"user-scalable=no, width=device-width\">"
        let html = "\(metaTag)\(htmlContent)"

        // Load HTML string to web view in main thread
        webView.loadHTMLString(html, baseURL: nil)
    }
}