import SwiftUI

enum Tab: String, CaseIterable, Hashable {
    case Library, Playlists, Search, Downloads, Settings

    var icon: String {
        switch self {
        case .Library: "square.stack.fill"
        case .Playlists: "music.note.list"
        case .Search: "magnifyingglass"
        case .Downloads: "arrow.down.circle.fill"
        case .Settings: "gearshape.fill"
        }
    }
}

enum Route: Hashable {
    case Artists, Albums, Songs, Playlists
    case Eq, EqFilters(profileId: String), EqFilterPage(profileId: String, filterId: String)
    case PlexAccount, StemServer, Quality, Storage, Appearance
    case ArtistPage(Artist), AlbumPage(Album), PlaylistPage(Playlist), StemPlaylistPage(String)
}

/// Tabs, their stacks and the Now Playing sheet: the things any screen can ask of the shell.
@MainActor
@Observable
final class Ui {
    var tab: Tab = .Library
    var paths: [Tab: [Route]] = [:]
    var nowPlayingOpen = false {
        didSet { overlays.level = nowPlayingOpen ? 1 : 0 }
    }
    let overlays: Overlays

    init(overlays: Overlays) { self.overlays = overlays }

    func path(_ t: Tab) -> Binding<[Route]> {
        Binding(get: { self.paths[t] ?? [] }, set: { self.paths[t] = $0 })
    }

    func push(_ r: Route) { paths[tab, default: []].append(r) }

    func pop() { if paths[tab]?.isEmpty == false { paths[tab]?.removeLast() } }

    /// Tapping the selected tab again pops it to its root.
    func selectTab(_ t: Tab) {
        if t == tab { paths[t] = [] } else { tab = t }
    }

    func openNowPlaying() { nowPlayingOpen = true }

    /// Switches to the Library tab and pushes [r] there.
    func showInLibrary(_ r: Route) {
        nowPlayingOpen = false
        tab = .Library
        paths[.Library, default: []].append(r)
    }

    /// Switches to Settings and opens [r] (the Equalizer) there.
    func showInSettings(_ r: Route) {
        nowPlayingOpen = false
        tab = .Settings
        if paths[.Settings]?.last != r { paths[.Settings, default: []].append(r) }
    }
}