YTItem: The Sealed Class Model for YouTube Music Content

sealed class YTItem {
    abstract val id: String
    abstract val title: String
    abstract val thumbnail: String?
    abstract val explicit: Boolean
    abstract val shareLink: String
}

data class SongItem(
    override val id: String,            // videoId (e.g. "dQw4w9WgXcQ")
    override val title: String,
    val artists: List<Artist>,
    val album: Album? = null,
    val duration: Int? = null,          // seconds
    val musicVideoType: String? = null,
    val chartPosition: Int? = null,
    val chartChange: String? = null,
    override val thumbnail: String,
    override val explicit: Boolean = false,
    val endpoint: WatchEndpoint? = null,
    val setVideoId: String? = null,
    val libraryAddToken: String? = null,
    val libraryRemoveToken: String? = null,
    val historyRemoveToken: String? = null,
    val viewCountText: String? = null,
) : YTItem()

val isVideoSong: Boolean
    get() = musicVideoType != null && musicVideoType != MUSIC_VIDEO_TYPE_ATV

data class AlbumItem(
    val browseId: String,               // e.g. "MPREb_..."
    val playlistId: String,             // e.g. "OLAK5uy_..."
    override val id: String = browseId, // aliases browseId
    override val title: String,
    val artists: List<Artist>?,
    val year: Int? = null,
    override val thumbnail: String,
    override val explicit: Boolean = false,
    val description: String? = null,
) : YTItem()

data class PlaylistItem(
    override val id: String,
    override val title: String,
    val author: Artist?,
    val songCountText: String?,
    override val thumbnail: String?,
    val playEndpoint: WatchEndpoint?,
    val shuffleEndpoint: WatchEndpoint?,
    val radioEndpoint: WatchEndpoint?,
    val isEditable: Boolean = false,
    val description: String? = null,
) : YTItem()

data class ArtistItem(
    override val id: String,
    override val title: String,
    override val thumbnail: String?,
    val channelId: String? = null,
    val playEndpoint: WatchEndpoint? = null,
    val shuffleEndpoint: WatchEndpoint?,
    val radioEndpoint: WatchEndpoint?,
    val subtext: String? = null,
) : YTItem()

data class Artist(
    val name: String,
    val id: String?,   // null when the artist has no browse page
)

data class Album(
    val name: String,
    val id: String,    // browseId of the album
)

fun describe(item: YTItem): String = when (item) {
    is SongItem -> buildString {
        append("🎵 ${item.title}")
        append(" by ${item.artists.joinToString { it.name }}")
        item.album?.let { append(" · ${it.name}") }
        item.duration?.let { append(" (${it / 60}:${(it % 60).toString().padStart(2, '0')})") }
        if (item.isVideoSong) append(" [Video]")
        if (item.explicit) append(" 🅴")
    }
    is AlbumItem -> buildString {
        append("💿 ${item.title}")
        item.artists?.let { append(" by ${it.joinToString { a -> a.name }}") }
        item.year?.let { append(" ($it)") }
    }
    is PlaylistItem -> buildString {
        append("📋 ${item.title}")
        item.author?.let { append(" · ${it.name}") }
        item.songCountText?.let { append(" · $it") }
    }
    is ArtistItem -> buildString {
        append("👤 ${item.title}")
        item.subtext?.let { append(" · $it") }
    }
}

// Remove explicit tracks (e.g. for parental controls)
fun <T : YTItem> List<T>.filterExplicit(enabled: Boolean = true): List<T>

// Remove music video SongItems, keeping only pure audio tracks
fun <T : YTItem> List<T>.filterVideoSongs(disableVideos: Boolean = false): List<T>

// Remove YouTube Shorts from playlist results (id starts with "SS")
fun <T : YTItem> List<T>.filterYoutubeShorts(enabled: Boolean = false): List<T>

viewModelScope.launch {
    YouTube.search("pop hits", SearchFilter.FILTER_SONG)
        .onSuccess { result ->
            val filtered = result.items
                .filterExplicit(enabled = userPrefs.hideExplicit)
                .filterVideoSongs(disableVideos = userPrefs.audioOnlyMode)

            adapter.submitList(filtered)
        }
}