Attractor/App/Reader View/ReaderViewController.swift

//
//  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 lazy var darkModeButton: UIBarButtonItem = {
        UIBarButtonItem(image: nil, 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() {
        darkModeButton.image = DarkModeControls.buttonImage(forDarkModeState: darkModeEnabled)
    }
    
    @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)
        }
    }
}