GoogleDocsViewController.swift

//
//  GoogleDocsViewController.swift
//  Created by laiso on 2018/06/12.
//
//    let gdViewController = GoogleDocsViewController(nibName: nil, bundle: nil)
//    gdViewController.url = "https://docs.google.com/document/.../pub"
//    let nav = UINavigationController(rootViewController: gdViewController)
//    self.present(nav, animated: true, completion: nil)
//

import UIKit
import WebKit

class GoogleDocsViewController: UIViewController {
    var url: String?
    private let webView = WKWebView()
    override func viewDidLoad() {
        super.viewDidLoad()
        
        guard
            let url = self.url,
            let reqUrl = URL(string: url) else {
                return
            }
        
        webView.navigationDelegate = self
        webView.load(URLRequest(url: reqUrl))
        self.view = webView
        
        navigationItem.leftBarButtonItem = UIBarButtonItem(barButtonSystemItem: .cancel, target: self, action: #selector(close))
    }
    
    @objc func close() {
        dismiss(animated: true) {
            self.webView.stopLoading()
        }
    }
}

extension GoogleDocsViewController: WKNavigationDelegate {
    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        webView.evaluateJavaScript("document.title") { result, err in
            assert(err == nil, err?.localizedDescription ?? "")
            self.title = result as? String
        }
        
        webView.evaluateJavaScript(
            ["document.getElementById('contents').style.margin='0 50px';",
             "document.getElementById('header').hidden=true;",
             "document.getElementById('footer').hidden=true;"].joined()) { result, err in
                assert(err == nil, err?.localizedDescription ?? "")
            }
    }
}