ipx/ios/Sources/CarScreen.swift

import CarPlay
import UIKit

// CarPlay (#420). A car shows no web view, so this is the app's own: three lists from ipx's API,
// In Progress, Unread and Shows, read as the badge reads it (API), and the same Playback the
// page drives, so a car's pick plays on with the phone locked and saves its place as the page's
// does. Now Playing is the system's, fed by Playback's now-playing info and remote commands.

/// An item as a car's list needs it: db.rs EntryRow, the fields used.
struct CarEpisode: Decodable {
    struct Enclosure: Decodable {
        let id: Int
        let url: String
        let mime: String?
        let deadair: Double?
        /// Set once ipx has the file; `/media/{id}` answers 404 before that.
        let path: String?
    }

    let guid: String
    let feed_id: String
    let title: String?
    let image: String?
    let duration: Double?
    let position: Double
    let enclosures: [Enclosure]

    /// The file to play: the first downloaded one that is sound (items.ts isPlayable, less video,
    /// which a car would play the sound of with nothing to say so). An item with none is not listed
    /// (#443): a post's picture or a file still to come is nothing a car can play.
    var audio: Enclosure? {
        enclosures.first { e in
            guard e.path != nil else { return false }
            let mime = (e.mime ?? "").lowercased()
            if !mime.isEmpty { return mime.hasPrefix("audio/") }
            let ext = URL(string: e.url)?.pathExtension.lowercased() ?? ""
            return ["mp3", "m4a", "m4b", "aac", "wav", "flac"].contains(ext)
        }
    }

    /// Its title, or the file's name: a car's list cannot show the opening of a post as the
    /// page's does, and "Untitled" twelve times says nothing.
    var name: String {
        if let t = title?.trimmingCharacters(in: .whitespacesAndNewlines), !t.isEmpty { return t }
        let file = audio.flatMap { URL(string: $0.url)?.deletingPathExtension().lastPathComponent }
        return file.flatMap { $0.isEmpty ? nil : $0.removingPercentEncoding ?? $0 } ?? "Untitled episode"
    }

    /// player.ts `mediaSrc`: the copy kept on the phone if there is one, else DeadAir's when it
    /// made one, so the clock the place is saved by is the one the page would use.
    static func path(of e: Enclosure, kept: Set<String>) -> String {
        let keepPath = (e.deadair ?? 0) > 0 ? "/media/\(e.id)/deadair" : "/media/\(e.id)"
        if kept.contains(keepPath) { return keepPath }
        return e.deadair != nil ? "/media/\(e.id)/deadair.m3u8" : "/media/\(e.id)"
    }

    /// What is left of it, once started: "12 min left".
    var left: String? {
        guard position > 5, let d = duration, d > position else { return nil }
        return "\(max(1, Int(((d - position) / 60).rounded()))) min left"
    }

    func item(feedTitle: String, feedImage: String?, kept: Set<String>) -> Playback.Item? {
        guard let enc = audio, let url = Server.resolveForPlayer(Self.path(of: enc, kept: kept)) else { return nil }
        return Playback.Item(url: url, enc: enc.id, feedId: feed_id, guid: guid, title: name,
                             feedTitle: feedTitle, artwork: image ?? feedImage,
                             duration: duration.map { Int($0) })
    }
}

/// A subscription, from `/api/feeds`.
struct CarFeed: Decodable {
    let id: String
    let title: String?
    let image: String?
    let unread: Int?
    let entries: Int?
    /// Its files ipx has downloaded.
    let downloaded: Int?
    let group: String?

    var name: String { title ?? id }
}

private struct CarPage: Decodable {
    let entries: [CarEpisode]
}

final class CarPlaySceneDelegate: UIResponder, CPTemplateApplicationSceneDelegate {
    private var screen: CarScreen?

    func templateApplicationScene(_ scene: CPTemplateApplicationScene,
                                  didConnect interfaceController: CPInterfaceController) {
        screen = CarScreen(interface: interfaceController)
    }

    func templateApplicationScene(_ scene: CPTemplateApplicationScene,
                                  didDisconnectInterfaceController interfaceController: CPInterfaceController) {
        screen = nil
    }
}

@MainActor
final class CarScreen: NSObject, CPTabBarTemplateDelegate {
    private let interface: CPInterfaceController
    private let inProgress = CPListTemplate(title: "In Progress", sections: [])
    private let unread = CPListTemplate(title: "Unread", sections: [])
    private let shows = CPListTemplate(title: "Shows", sections: [])
    private var feeds: [String: CarFeed] = [:]
    private var art: [String: UIImage] = [:]

    init(interface: CPInterfaceController) {
        self.interface = interface
        super.init()
        inProgress.tabImage = UIImage(systemName: "play.circle")
        unread.tabImage = UIImage(systemName: "tray.full")
        shows.tabImage = UIImage(systemName: "square.stack")
        let tabs = CPTabBarTemplate(templates: [inProgress, unread, shows])
        tabs.delegate = self
        interface.setRootTemplate(tabs, animated: false, completion: nil)
        refresh(inProgress)
    }

    /// Each list again whenever it is shown: a drive is long, and what was unread at the start
    /// has been heard by the end.
    func tabBarTemplate(_ tabBarTemplate: CPTabBarTemplate, didSelect selectedTemplate: CPTemplate) {
        refresh(selectedTemplate)
    }

    private func refresh(_ t: CPTemplate) {
        Task {
            await loadFeeds()
            // More than the car shows, since items with no file to play are dropped.
            switch t {
            case inProgress: await episodes(in: inProgress, from: "/api/entries?filter=in_progress&limit=100",
                                            empty: "Nothing started")
            case unread: await episodes(in: unread, from: "/api/entries?filter=unread&limit=100",
                                        empty: "Nothing unread")
            case shows: showFeeds()
            default: break
            }
        }
    }

    private func loadFeeds() async {
        guard let data = await API.get("/api/feeds"),
              let rows = try? JSONDecoder().decode([CarFeed].self, from: data) else { return }
        feeds = Dictionary(rows.map { ($0.id, $0) }, uniquingKeysWith: { a, _ in a })
    }

    private func episodes(in list: CPListTemplate, from path: String, empty: String, oneFeed: Bool = false) async {
        guard let data = await API.get(path), let page = try? JSONDecoder().decode(CarPage.self, from: data) else {
            unreachable(list)
            return
        }
        let kept = Set(Offline.shared.store.paths)
        let playing = Playback.shared.current
        let rows: [CPListItem] = page.entries.compactMap { e in
            let feed = feeds[e.feed_id]
            guard let item = e.item(feedTitle: feed?.name ?? e.feed_id, feedImage: feed?.image, kept: kept) else {
                return nil
            }
            // In a show's own list its name is the title above; across shows it is the detail.
            let detail = (oneFeed ? [e.left] : [item.feedTitle, e.left]).compactMap { $0 }.joined(separator: " · ")
            let row = CPListItem(text: item.title, detailText: detail.isEmpty ? nil : detail)
            row.isPlaying = playing?.guid == e.guid && playing?.feedId == e.feed_id
            row.handler = { [weak self] _, done in
                self?.play(item, from: e.position)
                done()
            }
            picture(item.artwork, for: row)
            return row
        }
        list.emptyViewTitleVariants = [empty]
        list.emptyViewSubtitleVariants = []
        list.updateSections([CPListSection(items: Array(rows.prefix(CPListTemplate.maximumItemCount)))])
    }

    /// Alphabetical, which a driver can find a show in without reading the whole list. Only
    /// shows with files downloaded (#443): a blog has nothing a car can play, and an OPML
    /// subscription's own row holds no items, its feeds do.
    private func showFeeds() {
        guard !feeds.isEmpty else {
            unreachable(shows)
            return
        }
        let sorted = feeds.values.filter { ($0.downloaded ?? 0) > 0 }
            .sorted { $0.name.localizedStandardCompare($1.name) == .orderedAscending }
        let rows: [CPListItem] = sorted.map { f in
            let n = f.unread ?? 0
            let row = CPListItem(text: f.name, detailText: n > 0 ? "\(n) unread" : nil)
            row.accessoryType = .disclosureIndicator
            row.handler = { [weak self] _, done in
                self?.open(f)
                done()
            }
            picture(f.image, for: row)
            return row
        }
        shows.emptyViewTitleVariants = ["No shows"]
        shows.emptyViewSubtitleVariants = []
        shows.updateSections([CPListSection(items: Array(rows.prefix(CPListTemplate.maximumItemCount)))])
    }

    private func open(_ f: CarFeed) {
        let list = CPListTemplate(title: f.name, sections: [])
        interface.pushTemplate(list, animated: true, completion: nil)
        let id = f.id.addingPercentEncoding(withAllowedCharacters: .alphanumerics) ?? f.id
        Task { await episodes(in: list, from: "/api/feeds/\(id)/entries?limit=100", empty: "No episodes", oneFeed: true) }
    }

    /// Signed out, or no connection. Sign-in is the page's, which a car cannot show.
    private func unreachable(_ list: CPListTemplate) {
        list.emptyViewTitleVariants = ["iPX can't reach your server"]
        list.emptyViewSubtitleVariants = ["Open iPX on your phone and sign in."]
        list.updateSections([])
    }

    private func play(_ item: Playback.Item, from position: Double) {
        Playback.shared.playChosen(item, startAt: position > 5 ? position : nil)
        interface.pushTemplate(CPNowPlayingTemplate.shared, animated: true, completion: nil)
    }

    /// A show's or an episode's picture, fetched through ipx's `/api/art` as the page's are, and
    /// kept for the drive: the lists are made again on every visit.
    private func picture(_ src: String?, for row: CPListItem) {
        guard let src else { return }
        if let image = art[src] {
            row.setImage(image)
            return
        }
        let path = src.lowercased().hasPrefix("http")
            ? "/api/art?u=" + (src.addingPercentEncoding(withAllowedCharacters: .alphanumerics) ?? src)
            : src
        Task {
            guard let data = await API.get(path), let image = UIImage(data: data) else { return }
            let size = CPListItem.maximumImageSize
            let small = UIGraphicsImageRenderer(size: size).image { _ in
                image.draw(in: CGRect(origin: .zero, size: size))
            }
            art[src] = small
            row.setImage(small)
        }
    }
}