//
//  Created by Jesse Squires
//  http://www.jessesquires.com
//
//
//  Documentation
//  http://jessesquires.github.io/JSQWebViewController
//
//
//  GitHub
//  https://github.com/jessesquires/JSQWebViewController
//
//
//  License
//  Copyright (c) 2015 Jesse Squires
//  Released under an MIT license: http://opensource.org/licenses/MIT
//

import UIKit
import WebKit


private let titleKeyPath = "title"
private let estimatedProgressKeyPath = "estimatedProgress"


/// An instance of `WebViewController` displays interactive web content.
open class WebViewController: UIViewController {

    // MARK: Properties

    /// Returns the web view for the controller.
    public final var webView: WKWebView {
        get {
            return _webView
        }
    }

    /// Returns the progress view for the controller.
    public final var progressBar: UIProgressView {
        get {
            return _progressBar
        }
    }

    /// The URL request for the web view. Upon setting this property, the web view immediately begins loading the request.
    public final var urlRequest: URLRequest {
        didSet {
            webView.load(urlRequest)
        }
    }

    /**
     Specifies whether or not to display the web view title as the navigation bar title.
     The default is `false`, which sets the navigation bar title to the URL host name of the URL request.
     */
    public final var displaysWebViewTitle: Bool = false

    // MARK: Private properties

    private final let configuration: WKWebViewConfiguration
    private final let activities: [UIActivity]?

    private lazy final var _webView: WKWebView = {
        let webView = WKWebView(frame: CGRect.zero, configuration: configuration)
        webView.addObserver(self, forKeyPath: titleKeyPath, options: .new, context: nil)
        webView.addObserver(self, forKeyPath: estimatedProgressKeyPath, options: .new, context: nil)
        webView.allowsBackForwardNavigationGestures = true
        if #available(iOS 9.0, *) {
            webView.allowsLinkPreview = true
        }
        return webView
    }()

    private lazy final var _progressBar: UIProgressView = {
        let progressBar = UIProgressView(progressViewStyle: .bar)
        progressBar.backgroundColor = .clear
        progressBar.trackTintColor = .clear
        return progressBar
    }()

    // MARK: Initialization

    /**
     Constructs a new `WebViewController`.

     - parameter urlRequest:    The URL request for the web view to load.
     - parameter configuration: The configuration for the web view.
     - parameter activities:    The custom activities to display in the `UIActivityViewController` that is presented when the action button is tapped.

     - returns: A new `WebViewController` instance.
     */
    public init(urlRequest: URLRequest, configuration: WKWebViewConfiguration = WKWebViewConfiguration(), activities: [UIActivity]? = nil) {
        self.configuration = configuration
        self.urlRequest = urlRequest
        self.activities = activities
        super.init(nibName: nil, bundle: nil)
    }

    /**
     Constructs a new `WebViewController`.

     - parameter url: The URL to display in the web view.

     - returns: A new `WebViewController` instance.
     */
    public convenience init(url: URL) {
        self.init(urlRequest: URLRequest(url: url))
    }

    /// :nodoc:
    public required init?(coder aDecoder: NSCoder) {
        self.configuration = WKWebViewConfiguration()
        self.urlRequest = URLRequest(url: URL(string: "http://")!)
        self.activities = nil
        super.init(coder: aDecoder)
    }

    deinit {
        webView.removeObserver(self, forKeyPath: titleKeyPath, context: nil)
        webView.removeObserver(self, forKeyPath: estimatedProgressKeyPath, context: nil)
    }


    // MARK: View lifecycle

    /// :nodoc:
    open override func viewDidLoad() {
        super.viewDidLoad()
        title = urlRequest.url?.host
        view.addSubview(_webView)
        view.addSubview(_progressBar)

        if presentingViewController?.presentedViewController != nil {
            navigationItem.leftBarButtonItem = UIBarButtonItem(barButtonSystemItem: .done,
                                                               target: self,
                                                               action: #selector(didTapDoneButton(_:)))
        }

        navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .action,
                                                            target: self,
                                                            action: #selector(didTapActionButton(_:)))

        webView.load(urlRequest)
    }

    /// :nodoc:
    open override func viewWillAppear(_ animated: Bool) {
        assert(navigationController != nil, "\(WebViewController.self) must be presented in a \(UINavigationController.self)")
        super.viewWillAppear(animated)
    }

    /// :nodoc:
    open override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
        webView.stopLoading()
    }

    /// :nodoc:
    open override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        webView.frame = view.bounds

        let isIOS11 = ProcessInfo.processInfo.isOperatingSystemAtLeast(
            OperatingSystemVersion(majorVersion: 11, minorVersion: 0, patchVersion: 0))
        let top = isIOS11 ? CGFloat(0.0) : topLayoutGuide.length
        let insets = UIEdgeInsets(top: top, left: 0, bottom: 0, right: 0)
        webView.scrollView.contentInset = insets
        webView.scrollView.scrollIndicatorInsets = insets

        view.bringSubview(toFront: progressBar)
        progressBar.frame = CGRect(x: view.frame.minX,
                                   y: topLayoutGuide.length,
                                   width: view.frame.size.width,
                                   height: 2)
    }


    // MARK: Actions

    @objc private func didTapDoneButton(_ sender: UIBarButtonItem) {
        dismiss(animated: true, completion: nil)
    }

    @objc private func didTapActionButton(_ sender: UIBarButtonItem) {
        if let url = urlRequest.url {
            let activityVC = UIActivityViewController(activityItems: [url], applicationActivities: activities)
            activityVC.popoverPresentationController?.barButtonItem = sender
            present(activityVC, animated: true, completion: nil)
        }
    }


    // MARK: KVO

    /// :nodoc:
    open override func observeValue(forKeyPath keyPath: String?,
                                    of object: Any?,
                                    change: [NSKeyValueChangeKey : Any]?,
                                    context: UnsafeMutableRawPointer?) {
        guard let theKeyPath = keyPath , object as? WKWebView == webView else {
            super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
            return
        }

        if displaysWebViewTitle && theKeyPath == titleKeyPath {
            title = webView.title
        }
        
        if theKeyPath == estimatedProgressKeyPath {
            updateProgress()
        }
    }
    
    // MARK: Private
    
    private final func updateProgress() {
        let completed = webView.estimatedProgress == 1.0
        progressBar.setProgress(completed ? 0.0 : Float(webView.estimatedProgress), animated: !completed)
        UIApplication.shared.isNetworkActivityIndicatorVisible = !completed
    }
}