//
//  BrowserViewController.swift
//  SBrowser
//
//  Created by James Magahern on 7/21/20.
//

import UIKit
import UniformTypeIdentifiers

class BrowserViewController: UIViewController, WKNavigationDelegate,
                             UITextFieldDelegate, ScriptPolicyViewControllerDelegate,
                             UIPopoverPresentationControllerDelegate, TabDelegate, TabPickerViewControllerDelegate
{
    let browserView = BrowserView()
    var tab: Tab { didSet { didChangeTab(tab) } }
    var webView: WKWebView { tab.webView }
    
    private let tabController = TabController()
    private let toolbarController = ToolbarViewController()
    
    private var policyManager: ResourcePolicyManager { tabController.policyManager }
    
    override var canBecomeFirstResponder: Bool { true }
    
    private var titleObservation: NSKeyValueObservation?
    private var loadingObservation: NSKeyValueObservation?
    private var backButtonObservation: NSKeyValueObservation?
    private var forwardButtonObservation: NSKeyValueObservation?
    
    override var preferredStatusBarStyle: UIStatusBarStyle { .lightContent }
    
    init() {
        self.tab = tabController.tabs.first!
        super.init(nibName: nil, bundle: nil)
        
        addChild(toolbarController)
        didChangeTab(tab)
    }
    
    required init?(coder: NSCoder) { fatalError("init(coder:) has not been implemented") }
    
    override func loadView() {
        browserView.toolbarView = toolbarController.toolbarView
        
        // Refresh button
        toolbarController.urlBar.refreshButton.addAction(UIAction(handler: { [webView] action in
            if webView.isLoading {
                webView.stopLoading()
            } else {
                webView.reload()
            }
        }), for: .touchUpInside)
        
        // Back button
        toolbarController.backButton.addAction(UIAction(handler: { [webView] _ in
            webView.goBack()
        }), for: .touchUpInside)
        
        // Forward button
        toolbarController.forwardButton.addAction(UIAction(handler: { [webView] _ in
            webView.goForward()
        }), for: .touchUpInside)
        
        // Share button
        toolbarController.shareButton.addAction(UIAction(handler: { [unowned self, webView, toolbarController] _ in
            if let url = webView.url {
                let itemProvider = NSItemProvider(item: url as NSURL, typeIdentifier: UTType.url.identifier)
                let config = UIActivityItemsConfiguration(itemProviders: [ itemProvider ])
                config.metadataProvider = { metadataKey in
                    switch metadataKey {
                        case .title: return webView.title
                        case .messageBody: return webView.title
                        default: return nil
                    }
                }
                
                config.previewProvider = { index, intent, suggestedSize in
                    NSItemProvider(item: self.tab.favicon, typeIdentifier: UTType.image.identifier)
                }
                
                let activityController = UIActivityViewController(activityItemsConfiguration: config)
                activityController.popoverPresentationController?.sourceView = toolbarController.shareButton
                self.present(activityController, animated: true, completion: nil)
            }
        }), for: .touchUpInside)
        
        // Script button
        toolbarController.scriptControllerIconView.addAction(UIAction(handler: { [unowned self] action in
            let hostOrigin = self.webView.url?.host ?? ""
            let loadedScripts = self.tab.allowedScriptOrigins.union(self.tab.blockedScriptOrigins)
            let scriptViewController = ScriptPolicyViewController(policyManager: self.policyManager,
                                                                  hostOrigin: hostOrigin,
                                                                  loadedScripts: loadedScripts,
                                                                  scriptsAllowedForTab: self.tab.javaScriptEnabled)
            scriptViewController.delegate = self
            
            let navController = UINavigationController(rootViewController: scriptViewController)
            navController.modalPresentationStyle = .popover
            navController.popoverPresentationController?.sourceView = self.toolbarController.scriptControllerIconView
            navController.popoverPresentationController?.delegate = self
            
            self.present(navController, animated: true, completion: nil)
        }), for: .touchUpInside)
        
        // Dark mode button
        toolbarController.darkModeButton.addAction(UIAction(handler: { [tab, toolbarController] _ in
            tab.bridge.darkModeEnabled = !tab.bridge.darkModeEnabled
            toolbarController.darkModeEnabled = tab.bridge.darkModeEnabled
        }), for: .touchUpInside)
        
        // Tabs button
        toolbarController.windowButton.addAction(UIAction(handler: { [unowned self] _ in
            let tabPickerController = TabPickerViewController(tabController: self.tabController)
            tabPickerController.delegate = self
            tabPickerController.selectedTab = self.tab
            
            let navController = UINavigationController(rootViewController: tabPickerController)
            navController.modalPresentationStyle = .popover
            navController.popoverPresentationController?.sourceView = self.toolbarController.windowButton
            navController.popoverPresentationController?.delegate = self

            self.present(navController, animated: true, completion: nil)
        }), for: .touchUpInside)
        
        // TextField delegate
        toolbarController.urlBar.textField.delegate = self
        
        self.view = browserView
    }
    
    private func updateLoadProgress(forWebView webView: WKWebView) {
        if webView.estimatedProgress == 1.0 {
            toolbarController.urlBar.loadProgress = .complete
        } else {
            toolbarController.urlBar.loadProgress = .loading(progress: webView.estimatedProgress)
        }
    }
    
    private func updateTitleAndURL(forWebView webView: WKWebView) {
        browserView.titlebarView.titleLabelView.text = webView.title
        
        if let urlString = webView.url?.absoluteString {
            toolbarController.urlBar.textField.text = urlString
        }
    }
    
    private func didChangeTab(_ tab: Tab) {
        tab.delegate = self
        
        let webView = tab.webView
        webView.allowsBackForwardNavigationGestures = true
        webView.navigationDelegate = self
        
        // Change webView
        browserView.webView = webView
        
        // Load progress
        updateLoadProgress(forWebView: webView)
        loadingObservation = webView.observe(\.estimatedProgress) { [unowned self] (webView, observedChange) in
            self.updateLoadProgress(forWebView: webView)
        }
        
        // Title observer
        updateTitleAndURL(forWebView: webView)
        titleObservation = webView.observe(\.title, changeHandler: { [unowned self] (webView, observedChange) in
            self.updateTitleAndURL(forWebView: webView)
        })
        
        // Back/forward observer
        toolbarController.backButton.isEnabled = webView.canGoBack
        backButtonObservation = webView.observe(\.canGoBack, changeHandler: { [toolbarController] (webView, observedChange) in
            toolbarController.backButton.isEnabled = webView.canGoBack
        })
        
        toolbarController.forwardButton.isEnabled = webView.canGoForward
        forwardButtonObservation = webView.observe(\.canGoForward, changeHandler: { [toolbarController] (webView, observedChange) in
            toolbarController.forwardButton.isEnabled = webView.canGoForward
        })
        
        // Script blocker button
        updateScriptBlockerButton()
        
        // Dark mode status
        toolbarController.darkModeEnabled = tab.bridge.darkModeEnabled
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        becomeFirstResponder()
    }
    
    private func updateScriptBlockerButton() {
        toolbarController.scriptControllerIconView.setBlockedScriptsNumber(tab.blockedScriptOrigins.count)
    }
        
    // MARK: UIPopoverPresentationControllerDelegate
    
    func adaptivePresentationStyle(for controller: UIPresentationController, traitCollection: UITraitCollection) -> UIModalPresentationStyle {
        // Forces popovers to present on iPhone
        return .none
    }
    
    // MARK: Navigation Delegate
    
    func webView(_ webView: WKWebView, didStartProvisionalNavigation navigation: WKNavigation!) {
        // Reset tracking this
        tab.blockedScriptOrigins.removeAll()
        
        updateTitleAndURL(forWebView: webView)
        
        // Start requesting favicon
        if let url = webView.url {
            tab.updateFaviconForURL(url)
        }
    }
    
    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        toolbarController.urlBar.loadProgress = .complete
    }
    
    func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, preferences: WKWebpagePreferences, decisionHandler: @escaping (WKNavigationActionPolicy, WKWebpagePreferences) -> Void)
    {
        var allowJavaScript = tab.javaScriptEnabled
        if !allowJavaScript, let host = navigationAction.request.url?.host {
            // Check origin policy
            allowJavaScript = policyManager.allowedOriginsForScriptResources().contains(host)
        }
        
        preferences.allowsContentJavaScript = allowJavaScript
        decisionHandler(.allow, preferences)
    }
    
    // MARK: UITextField Delegate
    
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        if let text = textField.text, let url = URL(string: text) {
            if url.scheme == nil {
                let urlString = "https://\(text)"
                if let url = URL(string: urlString) {
                    tab.beginLoadingURL(url)
                }
            }
        }
        
        textField.resignFirstResponder()
        return false
    }
    
    // MARK: Tab Delegate
    
    func didBlockScriptOrigin(_ origin: String, forTab: Tab) {
        updateScriptBlockerButton()
    }
    
    // MARK: Tab Picker Delegate
    
    func tabPicker(_ picker: TabPickerViewController, didSelectTab tab: Tab) {
        self.tab = tab
        picker.dismiss(animated: true, completion: nil)
    }
    
    func tabPicker(_ picker: TabPickerViewController, willCloseTab tab: Tab) {
        // If closed tab is current tab, pick another one.
        if tab == self.tab {
            if let nextTab = tabController.tabs.last(where: { $0 != tab }) {
                self.tab = nextTab
            }
            
            picker.dismiss(animated: true, completion: nil)
        }
    }
    
    // MARK: Script Policy View Controller Delegate
    
    func didChangeScriptPolicy() {
        tab.bridge.policyDataSourceDidChange()
        webView.reload()
    }
    
    func setScriptsEnabledForTab(_ enabled: Bool) {
        tab.javaScriptEnabled = enabled
    }
}