Adds customizable user script and user stylesheet.

App/Settings/CodeEditorSettingsViewController.swift

@@ -0,0 +1,82 @@
+//
+//  CodeEditorSettingsViewController.swift
+//  SBrowser
+//
+//  Copyright © 2021 Apple Inc. All rights reserved.
+//
+
+import UIKit
+
+class CodeEditorSettingsView: UIView
+{
+    public let textView = UITextView()
+    
+    override init(frame: CGRect) {
+        super.init(frame: frame)
+        
+        textView.font = .monospacedSystemFont(ofSize: 12.0, weight: .regular)
+        textView.autocorrectionType = .no
+        textView.autocapitalizationType = .none
+        textView.smartDashesType = .no
+        textView.smartQuotesType = .no
+        addSubview(textView)
+    }
+    
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+    
+    override func layoutSubviews() {
+        super.layoutSubviews()
+        textView.frame = bounds.inset(by: layoutMargins).insetBy(dx: 0.0, dy: 18.0)
+    }
+}
+
+class CodeEditorSettingsViewController: UIViewController, UITextViewDelegate
+{
+    private let settingsKeypath: ReferenceWritableKeyPath<Settings, String>
+    
+    private var saveTimer: Timer?
+    private let settingsView = CodeEditorSettingsView(frame: .zero)
+    
+    public init(settingsKeypath: ReferenceWritableKeyPath<Settings, String>) {
+        self.settingsKeypath = settingsKeypath
+        super.init(nibName: nil, bundle: nil)
+        
+        if settingsKeypath == \.userStylesheet {
+            tabBarItem.title = "Stylesheet"
+            tabBarItem.image = UIImage(systemName: "newspaper")
+        } else if settingsKeypath == \.userScript {
+            tabBarItem.title = "Script"
+            tabBarItem.image = UIImage(systemName: "applescript")
+        }
+    }
+    
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+    
+    override func loadView() {
+        self.view = settingsView
+    }
+    
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        settingsView.textView.delegate = self
+        settingsView.textView.text = Settings.shared[keyPath: settingsKeypath]
+    }
+    
+    private func saveContents() {
+        Settings.shared[keyPath: settingsKeypath] = settingsView.textView.text!
+    }
+    
+    func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
+        if self.saveTimer?.isValid == true { return true }
+        
+        self.saveTimer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: false, block: { [weak self] timer in
+            self?.saveContents()
+        })
+        
+        return true
+    }
+}

App/Settings/Settings.swift

@@ -28,6 +28,8 @@ public struct SettingProperty<T: RawRepresentable>
     }
 }
 
+// - These coercions into RawRepresentable are stupid. How do I write specializations for each type instead? 
+
 extension Dictionary: RawRepresentable where Key == String, Value == String {
     public typealias RawValue = [String: String]
     
@@ -41,6 +43,18 @@ extension Dictionary: RawRepresentable where Key == String, Value == String {
     }
 }
 
+extension String: RawRepresentable {
+    public typealias RawValue = String
+    
+    public init?(rawValue: String) {
+        self.init(rawValue)
+    }
+    
+    public var rawValue: String {
+        return self
+    }
+}
+
 class Settings
 {
     static let shared = Settings()
@@ -80,4 +94,10 @@ class Settings
         
         return nil
     }
+    
+    @SettingProperty(key: "userScript")
+    public var userScript: String = ""
+    
+    @SettingProperty(key: "userStylesheet")
+    public var userStylesheet: String = ""
 }

App/Settings/SettingsViewController.swift

@@ -30,6 +30,8 @@ class SettingsViewController: UITabBarController, NSToolbarDelegate
         self.viewControllers = [
             GeneralSettingsViewController(),
             RedirectRulesSettingsViewController(),
+            CodeEditorSettingsViewController(settingsKeypath: \.userScript),
+            CodeEditorSettingsViewController(settingsKeypath: \.userStylesheet),
         ]
         
         navigationItem.rightBarButtonItem = UIBarButtonItem(systemItem: .done, primaryAction: UIAction { [unowned self] _ in