//
//  ArticleViewController.swift
//  NetNewsWire
//
//  Created by Maurice Parker on 4/8/19.
//  Copyright © 2019 Ranchero Software. All rights reserved.
//

import UIKit
import WebKit
import Account
import Articles
import SafariServices
import RSCore

class ArticleViewController: UIViewController, MainControllerIdentifiable, Logging {
	
	typealias State = (extractedArticle: ExtractedArticle?,
					   isShowingExtractedArticle: Bool,
					   articleExtractorButtonState: ArticleExtractorButtonState,
					   windowScrollY: Int)
	
	@IBOutlet private weak var nextUnreadBarButtonItem: UIBarButtonItem!
	@IBOutlet private weak var prevArticleBarButtonItem: UIBarButtonItem!
	@IBOutlet private weak var nextArticleBarButtonItem: UIBarButtonItem!
	@IBOutlet private weak var readBarButtonItem: UIBarButtonItem!
	@IBOutlet private weak var starBarButtonItem: UIBarButtonItem!
	@IBOutlet private weak var actionBarButtonItem: UIBarButtonItem!
	@IBOutlet private weak var appearanceBarButtonItem: UIBarButtonItem!
	
	@IBOutlet private var searchBar: ArticleSearchBar!
	@IBOutlet private var searchBarBottomConstraint: NSLayoutConstraint!
	private var defaultControls: [UIBarButtonItem]?
	
	private var pageViewController: UIPageViewController!
	
	private var currentWebViewController: WebViewController? {
		return pageViewController?.viewControllers?.first as? WebViewController
	}
	
	private var articleExtractorButton: ArticleExtractorButton = {
		let button = ArticleExtractorButton(type: .system)
		button.frame = CGRect(x: 0, y: 0, width: 44.0, height: 44.0)
		button.setImage(AppAssets.articleExtractorOff, for: .normal)
		return button
	}()
	
	var mainControllerIdentifer = MainControllerIdentifier.article
	
	weak var coordinator: SceneCoordinator!
	
	private let poppableDelegate = PoppableGestureRecognizerDelegate()
	
	var article: Article? {
		didSet {
			if let controller = currentWebViewController, controller.article != article {
				controller.setArticle(article)
				DispatchQueue.main.async {
					// You have to set the view controller to clear out the UIPageViewController child controller cache.
					// You also have to do it in an async call or you will get a strange assertion error.
					self.pageViewController.setViewControllers([controller], direction: .forward, animated: false, completion: nil)
				}
			}
			updateUI()
		}
	}
	
	var restoreScrollPosition: (isShowingExtractedArticle: Bool, articleWindowScrollY: Int)? {
		didSet {
			if let rsp = restoreScrollPosition {
				currentWebViewController?.setScrollPosition(isShowingExtractedArticle: rsp.isShowingExtractedArticle, articleWindowScrollY: rsp.articleWindowScrollY)
			}
		}
	}
	
	var currentState: State? {
		guard let controller = currentWebViewController else { return nil}
		return State(extractedArticle: controller.extractedArticle,
					 isShowingExtractedArticle: controller.isShowingExtractedArticle,
					 articleExtractorButtonState: controller.articleExtractorButtonState,
					 windowScrollY: controller.windowScrollY)
	}
	
	var restoreState: State?
	
	private let keyboardManager = KeyboardManager(type: .detail)
	override var keyCommands: [UIKeyCommand]? {
		return keyboardManager.keyCommands
	}
	
	private var lastKnownDisplayMode: UISplitViewController.DisplayMode?

	var currentUnreadCount: Int = 0 {
		didSet {
			updateUnreadCountIndicator()
		}
	}
	
	override func viewDidLoad() {
		super.viewDidLoad()
		
		NotificationCenter.default.addObserver(self, selector: #selector(unreadCountDidChange(_:)), name: .UnreadCountDidChange, object: nil)
		NotificationCenter.default.addObserver(self, selector: #selector(statusesDidChange(_:)), name: .StatusesDidChange, object: nil)
		NotificationCenter.default.addObserver(self, selector: #selector(contentSizeCategoryDidChange(_:)), name: UIContentSizeCategory.didChangeNotification, object: nil)
		NotificationCenter.default.addObserver(self, selector: #selector(willEnterForeground(_:)), name: UIApplication.willEnterForegroundNotification, object: nil)
		NotificationCenter.default.addObserver(self, selector: #selector(reloadDueToThemeChange(_:)), name: .CurrentArticleThemeDidChangeNotification, object: nil)
		NotificationCenter.default.addObserver(self, selector: #selector(configureAppearanceMenu(_:)), name: .ArticleThemeNamesDidChangeNotification, object: nil)
		
		articleExtractorButton.addTarget(self, action: #selector(toggleArticleExtractor(_:)), for: .touchUpInside)
		toolbarItems?.insert(UIBarButtonItem(customView: articleExtractorButton), at: 6)
		
		if let parentNavController = navigationController?.parent as? UINavigationController {
			poppableDelegate.navigationController = parentNavController
			parentNavController.interactivePopGestureRecognizer?.delegate = poppableDelegate
		}
		
		navigationItem.leftItemsSupplementBackButton = true
		
		pageViewController = UIPageViewController(transitionStyle: .scroll, navigationOrientation: .horizontal, options: [:])
		pageViewController.delegate = self
		pageViewController.dataSource = self
		
		// This code is to disallow paging if we scroll from the left edge.  If this code is removed
		// PoppableGestureRecognizerDelegate will allow us to both navigate back and page back at the
		// same time. That is really weird when it happens.
		let panGestureRecognizer = UIPanGestureRecognizer()
		panGestureRecognizer.delegate = self
		pageViewController.scrollViewInsidePageControl?.addGestureRecognizer(panGestureRecognizer)
		
		pageViewController.view.translatesAutoresizingMaskIntoConstraints = false
		view.addSubview(pageViewController.view)
		addChild(pageViewController!)
		NSLayoutConstraint.activate([
			view.leadingAnchor.constraint(equalTo: pageViewController.view.leadingAnchor),
			view.trailingAnchor.constraint(equalTo: pageViewController.view.trailingAnchor),
			view.topAnchor.constraint(equalTo: pageViewController.view.topAnchor),
			view.bottomAnchor.constraint(equalTo: pageViewController.view.bottomAnchor)
		])
		
		let controller: WebViewController
		if let state = restoreState {
			controller = createWebViewController(article, updateView: false)
			controller.extractedArticle = state.extractedArticle
			controller.isShowingExtractedArticle = state.isShowingExtractedArticle
			controller.articleExtractorButtonState = state.articleExtractorButtonState
			controller.windowScrollY = state.windowScrollY
		} else {
			controller = createWebViewController(article, updateView: true)
		}
		
		if let rsp = restoreScrollPosition {
			controller.setScrollPosition(isShowingExtractedArticle: rsp.isShowingExtractedArticle, articleWindowScrollY: rsp.articleWindowScrollY)
		}
		
		articleExtractorButton.buttonState = controller.articleExtractorButtonState
		
		self.pageViewController.setViewControllers([controller], direction: .forward, animated: false, completion: nil)
		
		// Search bar
		searchBar.translatesAutoresizingMaskIntoConstraints = false
		NotificationCenter.default.addObserver(self, selector: #selector(beginFind(_:)), name: .FindInArticle, object: nil)
		NotificationCenter.default.addObserver(self, selector: #selector(endFind(_:)), name: .EndFindInArticle, object: nil)
		NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillChangeFrame(_:)), name: UIWindow.keyboardWillChangeFrameNotification, object: nil)
		searchBar.delegate = self
		view.bringSubviewToFront(searchBar)
		
		updateUI()
	}
	
	override func viewWillAppear(_ animated: Bool) {
		navigationController?.isToolbarHidden = false
		if AppDefaults.shared.articleFullscreenEnabled {
			currentWebViewController?.hideBars()
		}
		
		super.viewWillAppear(animated)
	}
	
	override func viewWillDisappear(_ animated: Bool) {
		super.viewWillDisappear(animated)
		if searchBar != nil && !searchBar.isHidden {
			endFind()
		}
	}
	
	override func viewSafeAreaInsetsDidChange() {
		// This will animate if the show/hide bars animation is happening.
		view.layoutIfNeeded()
	}
	
	func updateUI() {
		
		guard let article = article else {
			articleExtractorButton.isEnabled = false
			nextUnreadBarButtonItem.isEnabled = false
			prevArticleBarButtonItem.isEnabled = false
			nextArticleBarButtonItem.isEnabled = false
			readBarButtonItem.isEnabled = false
			starBarButtonItem.isEnabled = false
			actionBarButtonItem.isEnabled = false
			appearanceBarButtonItem.isEnabled = false
			return
		}
		
		nextUnreadBarButtonItem.isEnabled = coordinator.isAnyUnreadAvailable
		prevArticleBarButtonItem.isEnabled = coordinator.isPrevArticleAvailable
		nextArticleBarButtonItem.isEnabled = coordinator.isNextArticleAvailable
		readBarButtonItem.isEnabled = true
		starBarButtonItem.isEnabled = true
		appearanceBarButtonItem.isEnabled = true
		
		let permalinkPresent = article.preferredLink != nil
		var isFeedProvider = false
		if let webfeed = article.webFeed {
			isFeedProvider = webfeed.isFeedProvider
		}
		articleExtractorButton.isEnabled = permalinkPresent && !AppDefaults.shared.isDeveloperBuild && !isFeedProvider
		actionBarButtonItem.isEnabled = permalinkPresent
		
		if article.status.read {
			readBarButtonItem.image = AppAssets.circleOpenImage
			readBarButtonItem.isEnabled = article.isAvailableToMarkUnread
			readBarButtonItem.accLabelText = NSLocalizedString("Mark Article Unread", comment: "Mark Article Unread")
		} else {
			readBarButtonItem.image = AppAssets.circleClosedImage
			readBarButtonItem.isEnabled = true
			readBarButtonItem.accLabelText = NSLocalizedString("Selected - Mark Article Unread", comment: "Selected - Mark Article Unread")
		}
		
		if article.status.starred {
			starBarButtonItem.image = AppAssets.starClosedImage
			starBarButtonItem.accLabelText = NSLocalizedString("Selected - Star Article", comment: "Selected - Star Article")
		} else {
			starBarButtonItem.image = AppAssets.starOpenImage
			starBarButtonItem.accLabelText = NSLocalizedString("Star Article", comment: "Star Article")
		}
		
		configureAppearanceMenu()
		configureArticleExtractorMenu()
		
	}
	
	override func contentScrollView(for edge: NSDirectionalRectEdge) -> UIScrollView? {
		return currentWebViewController?.webView?.scrollView
	}
	
	
	/// The appearance menu is different on iPhone and iPad.
	/// On iPad, it's only the theme selector. On iPhone, the appearance menu
	/// contains the the theme selector and full screen options.
	/// - Parameter sender: `Any?`
	@objc
	func configureAppearanceMenu(_ sender: Any? = nil) {
		
		var themeActions = [UIAction]()
		
		for themeName in ArticleThemesManager.shared.themeNames {
			let action = UIAction(title: themeName,
								  image: nil,
								  identifier: nil,
								  discoverabilityTitle: nil,
								  attributes: [],
								  state: ArticleThemesManager.shared.currentTheme.name == themeName ? .on : .off,
								  handler: { action in
				ArticleThemesManager.shared.currentThemeName = themeName
			})
			themeActions.append(action)
		}
		
		let defaultThemeAction = UIAction(title: NSLocalizedString("Default", comment: "Default"),
										  image: nil,
										  identifier: nil,
										  discoverabilityTitle: nil,
										  attributes: [],
										  state: ArticleThemesManager.shared.currentTheme.name == AppDefaults.defaultThemeName ? .on : .off,
										  handler: { _ in
			ArticleThemesManager.shared.currentThemeName = AppDefaults.defaultThemeName
		})
		let defaultThemeMenu = UIMenu(title: "", image: nil, identifier: nil, options: .displayInline, children: [defaultThemeAction])
		let customThemeMenu = UIMenu(title: "", image: nil, identifier: nil, options: .displayInline, children: themeActions)
		
		let themeMenu = UIMenu(title: "Theme", image: AppAssets.themeImage, identifier: nil, options: .singleSelection, children: [ defaultThemeMenu, customThemeMenu])
		
		if UIDevice.current.userInterfaceIdiom == .pad {
			appearanceBarButtonItem.image = AppAssets.themeImage
			appearanceBarButtonItem.menu = themeMenu
			return
		}
		
		var appearanceChildren: [UIMenuElement] = [themeMenu]
		
		if let currentWebViewController = currentWebViewController {
			if currentWebViewController.isFullScreenAvailable {
				let fullScreenAction = UIAction(title: NSLocalizedString("Full Screen", comment: "Full Screen"),
												image: UIImage(systemName: "arrow.up.backward.and.arrow.down.forward"),
												identifier: nil,
												discoverabilityTitle: nil,
												attributes: [],
												state: .off) { [weak self] _ in
					self?.currentWebViewController?.hideBars()
					if AppDefaults.shared.hasUsedFullScreenPreviously == false {
						let alert = UIAlertController(title: NSLocalizedString("Exit Full Screen", comment: "Full Screen"),
													  message: NSLocalizedString("To exit Full Screen mode tap the top of the screen.\n\nYou'll only see this message once.", comment: "Full screen explainer."),
													  preferredStyle: .alert)
						alert.addAction(UIAlertAction(title: NSLocalizedString("Dismiss", comment: "Dismiss"), style: .default, handler: { _ in
							AppDefaults.shared.hasUsedFullScreenPreviously = true
						}))
						self?.present(alert, animated: true, completion: nil)
					}
				}
				appearanceChildren.append(fullScreenAction)
			}
		}
		
		appearanceBarButtonItem.image = AppAssets.articleAppearanceImage
		appearanceBarButtonItem.menu = UIMenu(title: NSLocalizedString("Article Appearance", comment: "Appearance"), children: appearanceChildren)
	}
	
	private func configureArticleExtractorMenu() {
		if let feed = article?.webFeed {
			let extractorOn = feed.isArticleExtractorAlwaysOn ?? false
			let readerAction = UIAction(title: NSLocalizedString("Always Use Reader View", comment: "Always Use Reader View"),
										image: AppAssets.articleExtractorOffSF,
										identifier: nil,
										discoverabilityTitle: nil,
										attributes: [],
										state: extractorOn ? .on : .off) { [weak self] _ in
				if feed.isArticleExtractorAlwaysOn == nil {
					feed.isArticleExtractorAlwaysOn = true
				} else {
					feed.isArticleExtractorAlwaysOn?.toggle()
				}
				self?.configureArticleExtractorMenu()
			}
			let menu = UIMenu(title: feed.nameForDisplay, image: AppAssets.articleExtractorOffSF, identifier: nil, options: .displayInline, children: [readerAction])
			articleExtractorButton.menu = menu
			articleExtractorButton.showsMenuAsPrimaryAction = false
		}
	}
	
	
	@objc
	func reloadDueToThemeChange(_ notification: Notification) {
		currentWebViewController?.fullReload()
		configureAppearanceMenu()
	}
	
	// MARK: Notifications
	
	@objc dynamic func unreadCountDidChange(_ notification: Notification) {
		updateUI()
	}
	
	@objc func statusesDidChange(_ note: Notification) {
		guard let articleIDs = note.userInfo?[Account.UserInfoKey.articleIDs] as? Set<String> else {
			return
		}
		guard let article = article else {
			return
		}
		if articleIDs.contains(article.articleID) {
			updateUI()
		}
	}
	
	@objc func contentSizeCategoryDidChange(_ note: Notification) {
		currentWebViewController?.fullReload()
	}
	
	@objc func willEnterForeground(_ note: Notification) {
		// The toolbar will come back on you if you don't hide it again
		if AppDefaults.shared.articleFullscreenEnabled {
			currentWebViewController?.hideBars()
		}
	}
	
	// MARK: Actions
	
	@objc func showBars(_ sender: Any) {
		currentWebViewController?.showBars()
	}
	
	@IBAction func toggleArticleExtractor(_ sender: Any) {
		currentWebViewController?.toggleArticleExtractor()
		configureArticleExtractorMenu()
	}
	
	@IBAction func nextUnread(_ sender: Any) {
		coordinator.selectNextUnread()
	}
	
	@IBAction func prevArticle(_ sender: Any) {
		coordinator.selectPrevArticle()
	}
	
	@IBAction func nextArticle(_ sender: Any) {
		coordinator.selectNextArticle()
	}
	
	@IBAction func toggleRead(_ sender: Any) {
		coordinator.toggleReadForCurrentArticle()
	}
	
	@IBAction func toggleStar(_ sender: Any) {
		coordinator.toggleStarredForCurrentArticle()
	}
	
	@IBAction func showActivityDialog(_ sender: Any) {
		currentWebViewController?.showActivityDialog(popOverBarButtonItem: actionBarButtonItem)
	}
	
	@objc func toggleReaderView(_ sender: Any?) {
		currentWebViewController?.toggleArticleExtractor()
	}
	
	// MARK: Keyboard Shortcuts
	
	@objc func navigateToTimeline(_ sender: Any?) {
		coordinator.navigateToTimeline()
	}
	
	// MARK: API
	
	func focus() {
		currentWebViewController?.focus()
	}
	
	func canScrollDown() -> Bool {
		return currentWebViewController?.canScrollDown() ?? false
	}
	
	func canScrollUp() -> Bool {
		return currentWebViewController?.canScrollUp() ?? false
	}
	
	func scrollPageDown() {
		currentWebViewController?.scrollPageDown()
	}
	
	func scrollPageUp() {
		currentWebViewController?.scrollPageUp()
	}
	
	func stopArticleExtractorIfProcessing() {
		currentWebViewController?.stopArticleExtractorIfProcessing()
	}
	
	func openInAppBrowser() {
		currentWebViewController?.openInAppBrowser()
	}
	
	func setScrollPosition(isShowingExtractedArticle: Bool, articleWindowScrollY: Int) {
		currentWebViewController?.setScrollPosition(isShowingExtractedArticle: isShowingExtractedArticle, articleWindowScrollY: articleWindowScrollY)
	}
	
	public func splitViewControllerWillChangeTo(displayMode: UISplitViewController.DisplayMode) {
		lastKnownDisplayMode = displayMode
		updateUnreadCountIndicator()
	}
	
}

// MARK: Find in Article
public extension Notification.Name {
	static let FindInArticle = Notification.Name("FindInArticle")
	static let EndFindInArticle = Notification.Name("EndFindInArticle")
}

extension ArticleViewController: SearchBarDelegate {
	
	func searchBar(_ searchBar: ArticleSearchBar, textDidChange searchText: String) {
		currentWebViewController?.searchText(searchText) {
			found in
			searchBar.resultsCount = found.count
			
			if let index = found.index {
				searchBar.selectedResult = index + 1
			}
		}
	}
	
	func doneWasPressed(_ searchBar: ArticleSearchBar) {
		NotificationCenter.default.post(name: .EndFindInArticle, object: nil)
	}
	
	func nextWasPressed(_ searchBar: ArticleSearchBar) {
		if searchBar.selectedResult < searchBar.resultsCount {
			currentWebViewController?.selectNextSearchResult()
			searchBar.selectedResult += 1
		}
	}
	
	func previousWasPressed(_ searchBar: ArticleSearchBar) {
		if searchBar.selectedResult > 1 {
			currentWebViewController?.selectPreviousSearchResult()
			searchBar.selectedResult -= 1
		}
	}
}

extension ArticleViewController {
	
	@objc func beginFind(_ _: Any? = nil) {
		searchBar.isHidden = false
		navigationController?.setToolbarHidden(true, animated: true)
		currentWebViewController?.additionalSafeAreaInsets.bottom = searchBar.frame.height
		searchBar.becomeFirstResponder()
	}
	
	@objc func endFind(_ _: Any? = nil) {
		searchBar.resignFirstResponder()
		searchBar.isHidden = true
		navigationController?.setToolbarHidden(false, animated: true)
		currentWebViewController?.additionalSafeAreaInsets.bottom = 0
		currentWebViewController?.endSearch()
	}
	
	@objc func keyboardWillChangeFrame(_ notification: Notification) {
		if !searchBar.isHidden,
		   let duration = notification.userInfo?[UIWindow.keyboardAnimationDurationUserInfoKey] as? Double,
		   let curveRaw = notification.userInfo?[UIWindow.keyboardAnimationCurveUserInfoKey] as? UInt,
		   let frame = notification.userInfo?[UIWindow.keyboardFrameEndUserInfoKey] as? CGRect {
			
			let curve = UIView.AnimationOptions(rawValue: curveRaw)
			let newHeight = view.safeAreaLayoutGuide.layoutFrame.maxY - frame.minY
			currentWebViewController?.additionalSafeAreaInsets.bottom = newHeight + searchBar.frame.height + 10
			self.searchBarBottomConstraint.constant = newHeight
			UIView.animate(withDuration: duration, delay: 0, options: curve, animations: {
				self.view.layoutIfNeeded()
			})
		}
	}
	
}


// MARK: WebViewControllerDelegate

extension ArticleViewController: WebViewControllerDelegate {
	
	func webViewController(_ webViewController: WebViewController, articleExtractorButtonStateDidUpdate buttonState: ArticleExtractorButtonState) {
		if webViewController === currentWebViewController {
			articleExtractorButton.buttonState = buttonState
		}
	}
	
}

// MARK: UIPageViewControllerDataSource

extension ArticleViewController: UIPageViewControllerDataSource {
	
	func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
		guard let webViewController = viewController as? WebViewController,
			  let currentArticle = webViewController.article,
			  let article = coordinator.findPrevArticle(currentArticle) else {
				  return nil
			  }
		return createWebViewController(article)
	}
	
	func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
		guard let webViewController = viewController as? WebViewController,
			  let currentArticle = webViewController.article,
			  let article = coordinator.findNextArticle(currentArticle) else {
				  return nil
			  }
		return createWebViewController(article)
	}
	
}

// MARK: UIPageViewControllerDelegate

extension ArticleViewController: UIPageViewControllerDelegate {
	
	func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
		guard finished, completed else { return }
		guard let article = currentWebViewController?.article else { return }
		
		coordinator.selectArticle(article, animations: [.select, .scroll, .navigation])
		articleExtractorButton.buttonState = currentWebViewController?.articleExtractorButtonState ?? .off
		
		previousViewControllers.compactMap({ $0 as? WebViewController }).forEach({ $0.stopWebViewActivity() })
	}
	
}

// MARK: UIGestureRecognizerDelegate

extension ArticleViewController: UIGestureRecognizerDelegate {
	
	func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
		return true
	}
	
	func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
		let point = gestureRecognizer.location(in: nil)
		if point.x > 40 {
			return true
		}
		return false
	}
	
}

// MARK: Private

private extension ArticleViewController {
	
	func createWebViewController(_ article: Article?, updateView: Bool = true) -> WebViewController {
		let controller = WebViewController()
		controller.coordinator = coordinator
		controller.delegate = self
		controller.setArticle(article, updateView: updateView)
		return controller
	}
	
	func updateUnreadCountIndicator() {
		if currentUnreadCount > 0 && (traitCollection.userInterfaceIdiom == .phone || lastKnownDisplayMode == .secondaryOnly) {
			let unreadCountView = MasterTimelineUnreadCountView(frame: .zero)
			unreadCountView.unreadCount = currentUnreadCount
			unreadCountView.setFrameIfNotEqual(CGRect(x: 0, y: 0, width: unreadCountView.intrinsicContentSize.width, height: unreadCountView.intrinsicContentSize.height))
			navigationItem.leftBarButtonItem = UIBarButtonItem(customView: unreadCountView)
		} else  {
			navigationItem.leftBarButtonItem = nil
		}
	}
	
}