import Combine
import SwiftUI
import UIKit

/// What the window holds: the native interface, with ipx's page a button away.
///
/// The page is not a fallback here, it is the rest of the app. Settings, the admin page, the
/// directory and OPML have never been native and are not meant to be (#5), and an item's show
/// notes are still HTML (#4). Both live behind the same web view that used to be the whole
/// interface, so nothing has been lost by putting a list in front of it.
final class RootViewController: UIViewController {
    private let api = API()
    private var store: LibraryStore!
    private var cookies: CookieBridge!
    private var playback: Playback!
    private var page: WebViewController!
    private var host: UIHostingController<AnyView>!
    private var watching: AnyCancellable?

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

        // The page is built first and kept: it owns the web view whose cookies authenticate
        // everything, including the API client and the player. Signing in happens there.
        page = WebViewController()
        page.loadViewIfNeeded()
        cookies = page.cookieBridge
        playback = page.player

        store = LibraryStore(api: api)

        let root = LibraryView(
            store: store,
            playback: playback,
            play: { [weak self] entry, file in self?.play(entry, file) },
            openPage: { [weak self] in self?.showPage() })
            .environment(\.api, api)

        host = UIHostingController(rootView: AnyView(root))
        addChild(host)
        host.view.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(host.view)
        NSLayoutConstraint.activate([
            host.view.topAnchor.constraint(equalTo: view.topAnchor),
            host.view.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            host.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            host.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
        ])
        host.didMove(toParent: self)

        // preferredColorScheme inside a hosting controller does not reliably reach the whole
        // hierarchy -- the list stayed light against a dark account. Overriding the style on the
        // controller does, and it carries to the page presented over it as well.
        watching = store.$appearance.sink { [weak self] scheme in
            let style: UIUserInterfaceStyle
            switch scheme {
            case .some(.dark): style = .dark
            case .some(.light): style = .light
            default: style = .unspecified
            }
            self?.overrideUserInterfaceStyle = style
        }
    }

    /// Plays a row through the same Playback the lock screen and the car drive.
    private func play(_ entry: IPX.Entry, _ asked: IPX.Enclosure?) {
        guard let file = asked ?? entry.playable,
              let url = ServerSettings.url("/media/\(file.id)") else { return }
        let feed = store.feed(entry.feedId)
        playback.load(.init(
            url: url,
            feedId: entry.feedId,
            guid: entry.guid,
            title: entry.title ?? "",
            feedTitle: feed?.name ?? entry.feedId,
            artwork: entry.image ?? feed?.image,
            position: entry.position,
            duration: entry.duration))
        // Where it starts is the entry's own position, since there is no page here to decide it.
        if entry.position > 5 { playback.seek(to: Double(entry.position)) }
        playback.play()
    }

    private func showPage() {
        guard page.presentingViewController == nil else { return }
        let nav = UINavigationController(rootViewController: page)
        page.navigationItem.leftBarButtonItem = UIBarButtonItem(
            systemItem: .done, primaryAction: UIAction { [weak self] _ in
                self?.dismiss(animated: true)
                // The page may have changed read state or subscriptions while it was open.
                Task { await self?.store.refreshFeeds(); self?.store.reload() }
            })
        present(nav, animated: true)
    }
}