ipodderx-app/ios/Sources/WebViewController.swift

import SwiftUI
import UIKit
import WebKit

/// The app, very nearly: ipx's own page, full screen.
///
/// What it adds is the bridge to the host's player, a way to say which server, and a line of
/// honesty when something is wrong.
final class WebViewController: UIViewController, WKNavigationDelegate {
    private var webView: WKWebView!
    private var cookies: CookieBridge!
    private var api: API!
    private var playback: Playback!

    /// The web view's cookie store is what authenticates everything else, and its Playback is
    /// the one the lock screen drives, so the native interface borrows both rather than making
    /// a second of either.
    var cookieBridge: CookieBridge { cookies }
    var player: Playback { playback }
    private var bridge: Bridge!

    private let banner = UIView()
    private let bannerText = UILabel()
    private var checkedBridge = false
    /// The page sits below the banner when there is one, and at the top when there is not. Two
    /// constraints rather than an overlay: the banner covered the page's own toolbar, and ipx
    /// lays that out itself, so there is nothing to scroll out of the way.
    private var pageBelowBanner: NSLayoutConstraint!
    private var pageAtTop: NSLayoutConstraint!

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .black

        let cfg = WKWebViewConfiguration()
        // The persistent store, so a sign-in through Cloudflare Access survives a relaunch --
        // and so there are cookies for the player to use at all.
        cfg.websiteDataStore = .default()
        cfg.allowsInlineMediaPlayback = true
        // Video still plays in the page, and it should not need a second tap to start.
        cfg.mediaTypesRequiringUserActionForPlayback = []

        webView = WKWebView(frame: .zero, configuration: cfg)
        webView.navigationDelegate = self
        webView.allowsBackForwardNavigationGestures = false
        webView.scrollView.contentInsetAdjustmentBehavior = .never
        webView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(webView)
        pageAtTop = webView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor)
        NSLayoutConstraint.activate([
            pageAtTop,
            webView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            webView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            webView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor),
        ])

        cookies = CookieBridge(store: cfg.websiteDataStore.httpCookieStore)
        api = API()
        playback = Playback(cookies: cookies, api: api)
        bridge = Bridge(webView: webView, playback: playback)
        bridge.onReady = { [weak self] _ in
            self?.checkedBridge = true
            self?.setBanner(nil)
        }
        cfg.userContentController.add(bridge, name: Bridge.handlerName)
        Zoom.install(into: cfg.userContentController)

        setUpBanner()

        if ServerSettings.isConfigured { load() }
    }

    // MARK: - how big the page is drawn

    /// The page is sized for a phone and for a browser window, and on a Mac -- where the window
    /// is often two thousand points across -- it reads small. Scaling it here rather than asking
    /// ipx to carry a text size: the page is right everywhere else, and this is the one place
    /// that is wrong.
    enum Zoom {
        private static let key = "ipx.zoom"
        static let steps: [Double] = [1.0, 1.15, 1.25, 1.4, 1.6, 1.8, 2.0]

        /// A Mac starts bigger; a phone and an iPad are already right.
        static var normal: Double {
            #if targetEnvironment(macCatalyst)
            return 1.25
            #else
            return 1.0
            #endif
        }

        static var current: Double {
            get {
                let v = UserDefaults.standard.double(forKey: key)
                return steps.contains(v) ? v : normal
            }
            set { UserDefaults.standard.set(newValue, forKey: key) }
        }

        /// pageZoom alone spilled the page off the screen: ipx's body is `height:100dvh`, and
        /// WebKit measures dvh against the unzoomed window, so the page laid itself out at the
        /// window's full size and was then scaled up. A percentage of the root resolves against
        /// a box that does know about zoom, which is the whole of the fix.
        /// CSS zoom, not WKWebView.pageZoom. pageZoom scales what is drawn but leaves the
        /// layout box the size of the window, so ipx's full-height page -- body is 100dvh --
        /// laid itself out at the window's height and then got scaled past the bottom of it.
        /// CSS zoom is part of layout, so the page measures itself correctly; body's own width
        /// and height are divided back out because its containing block is not zoomed.
        static func script(_ zoom: Double) -> String {
            // No width. A percentage resolves against the containing block in the zoomed
            // element's own units, so 100% is already the full width -- dividing it again left
            // the page filling four fifths of the window and then three fifths as the zoom went
            // up. A block fills its container by itself. dvh is the exception: viewport units do
            // not know about zoom, so the height does have to be divided back out.
            let css = zoom == 1 ? "" : "body{zoom:\(zoom);height:calc(100dvh/\(zoom))!important}"
            return "(function(){var id='ipx-zoom';var s=document.getElementById(id);"
                + "if(!s){s=document.createElement('style');s.id=id;"
                + "(document.head||document.documentElement).appendChild(s)}"
                + "s.textContent=\(css.debugDescription)})()"
        }

        /// The page's own player bar, hidden. It is still what the play buttons drive -- they
        /// post to the host either way -- but the bar itself is ours now.
        static let hidePageBar = "(function(){var s=document.createElement('style');"
            + "s.textContent='#player{display:none!important}';"
            + "(document.head||document.documentElement).appendChild(s)})()"

        static func install(into controller: WKUserContentController) {
            controller.addUserScript(WKUserScript(source: hidePageBar,
                                                  injectionTime: .atDocumentEnd,
                                                  forMainFrameOnly: true))
            controller.addUserScript(WKUserScript(source: script(current),
                                                  injectionTime: .atDocumentEnd,
                                                  forMainFrameOnly: true))
        }
    }

    override var keyCommands: [UIKeyCommand]? {
        // The page's own shortcuts are single keys and ignore a modifier, so these do not collide.
        [
            UIKeyCommand(title: "Bigger", action: #selector(zoomIn), input: "+", modifierFlags: .command),
            UIKeyCommand(title: "Bigger", action: #selector(zoomIn), input: "=", modifierFlags: .command),
            UIKeyCommand(title: "Smaller", action: #selector(zoomOut), input: "-", modifierFlags: .command),
            UIKeyCommand(title: "Actual Size", action: #selector(zoomReset), input: "0", modifierFlags: .command),
        ]
    }

    @objc private func zoomIn() { step(+1) }
    @objc private func zoomOut() { step(-1) }
    @objc private func zoomReset() { apply(Zoom.normal) }

    private func step(_ by: Int) {
        let steps = Zoom.steps
        let at = steps.firstIndex(of: Zoom.current) ?? 0
        apply(steps[min(steps.count - 1, max(0, at + by))])
    }

    private func apply(_ zoom: Double) {
        Zoom.current = zoom
        webView.evaluateJavaScript(Zoom.script(zoom))
    }

    // MARK: - which server

    /// Shake to change it. There is nowhere on screen to put a button -- the page fills it, and
    /// this is a setting touched about once -- so the way back is a gesture and the banner.
    override var canBecomeFirstResponder: Bool { true }
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        becomeFirstResponder()
        // Not from viewDidLoad: presenting before the view is in a window gets you a blank screen
        // and no error, which is exactly what it did.
        if !ServerSettings.isConfigured && presentedViewController == nil {
            showSetup(animated: animated)
        }
    }
    override func motionEnded(_ motion: UIEvent.EventSubtype, with event: UIEvent?) {
        if motion == .motionShake && presentedViewController == nil { showSetup(animated: true) }
    }

    @objc private func showSetup() { showSetup(animated: true) }

    private func showSetup(animated: Bool) {
        let setup = ServerSetupViewController(first: !ServerSettings.isConfigured)
        setup.onSave = { [weak self] _ in
            self?.dismiss(animated: true)
            self?.setBanner(nil)
            self?.playback.stop()
            self?.load()
        }
        let nav = UINavigationController(rootViewController: setup)
        // A first run has nothing behind it, so it cannot be swiped away unanswered.
        nav.isModalInPresentation = !ServerSettings.isConfigured
        present(nav, animated: animated)
    }

    private func load() {
        guard let base = ServerSettings.base else { return showSetup(animated: true) }
        // Sync first: the page is fetched with the cookies too, and without them the first
        // request is a redirect to a sign-in that is not actually needed.
        cookies.sync { [weak self] in
            DispatchQueue.main.async { self?.webView.load(URLRequest(url: base)) }
        }
    }

    // MARK: - navigation

    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        // The bridge announces itself on load. A server whose page predates it never will, and the
        // app would otherwise look identical while playing nothing in the background.
        checkedBridge = false
        DispatchQueue.main.asyncAfter(deadline: .now() + 2) { [weak self] in
            guard let self, !self.checkedBridge else { return }
            self.webView.evaluateJavaScript("!!(window.ipxNative)") { got, _ in
                if (got as? Bool) != true {
                    self.setBanner("This server's page has no native bridge. Playback stays in the app; "
                                   + "background and car playback are off.")
                }
            }
        }
    }

    func webView(_ webView: WKWebView, didFail navigation: WKNavigation!, withError error: Error) {
        showFailure(error)
    }

    func webView(_ webView: WKWebView, didFailProvisionalNavigation navigation: WKNavigation!, withError error: Error) {
        showFailure(error)
    }

    private func showFailure(_ error: Error) {
        // -999 is a load cancelled because another started, which is not a failure to report.
        if (error as NSError).code == NSURLErrorCancelled { return }
        let host = ServerSettings.base?.host ?? "the server"
        setBanner("Cannot reach \(host): \(error.localizedDescription)")
    }

    // MARK: - the banner

    private func setUpBanner() {
        banner.backgroundColor = UIColor(red: 0.55, green: 0.12, blue: 0.12, alpha: 1)
        banner.isHidden = true
        banner.translatesAutoresizingMaskIntoConstraints = false

        bannerText.numberOfLines = 0
        bannerText.font = .preferredFont(forTextStyle: .footnote)
        bannerText.textColor = .white

        let change = UIButton(type: .system)
        change.setTitle("Server", for: .normal)
        change.titleLabel?.font = .preferredFont(forTextStyle: .footnote)
        change.tintColor = .white
        change.setContentHuggingPriority(.required, for: .horizontal)
        // Without this the label takes the whole row and the button truncates to an ellipsis,
        // which is not a thing anyone will tap.
        change.setContentCompressionResistancePriority(.required, for: .horizontal)
        change.addTarget(self, action: #selector(showSetup as () -> Void), for: .touchUpInside)

        let dismiss = UIButton(type: .system)
        dismiss.setImage(UIImage(systemName: "xmark"), for: .normal)
        dismiss.tintColor = .white
        dismiss.accessibilityLabel = "Hide this message"
        dismiss.setContentHuggingPriority(.required, for: .horizontal)
        dismiss.setContentCompressionResistancePriority(.required, for: .horizontal)
        dismiss.addTarget(self, action: #selector(hideBanner), for: .touchUpInside)

        let row = UIStackView(arrangedSubviews: [bannerText, change, dismiss])
        row.spacing = 12
        row.alignment = .center
        row.isLayoutMarginsRelativeArrangement = true
        row.layoutMargins = .init(top: 8, left: 12, bottom: 8, right: 12)
        row.translatesAutoresizingMaskIntoConstraints = false
        banner.addSubview(row)

        view.addSubview(banner)
        pageBelowBanner = webView.topAnchor.constraint(equalTo: banner.bottomAnchor)
        NSLayoutConstraint.activate([
            banner.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
            banner.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            banner.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            row.topAnchor.constraint(equalTo: banner.topAnchor),
            row.bottomAnchor.constraint(equalTo: banner.bottomAnchor),
            row.leadingAnchor.constraint(equalTo: banner.leadingAnchor),
            row.trailingAnchor.constraint(equalTo: banner.trailingAnchor),
        ])
    }

    /// Dismissed by hand. It says something true, but it says it once -- a permanent stripe
    /// across a page that otherwise works is worse than the thing it is warning about.
    @objc private func hideBanner() { setBanner(nil) }

    private func setBanner(_ text: String?) {
        bannerText.text = text
        banner.isHidden = text == nil
        pageAtTop.isActive = text == nil
        pageBelowBanner.isActive = text != nil
        view.layoutIfNeeded()
    }

    override var preferredStatusBarStyle: UIStatusBarStyle { .lightContent }
}