/* The library, as the phone reads it: albums from library.db, the recents
   from the play history, follows and playlists. One store, loaded once at
   launch; the pieces that change (recents) are re-read when they do. */
import * as api from "../lib/api.js";
import { listen } from "../lib/events.js";

export const lib = $state({
    albums: [],
    recents: [],    // library rows only, with an album_id
    follows: [],
    playlists: [],
    /** album id → { secs, bytes, avg_kbps, bit_depth, sample_rate, formats, last_played_at } — the desktop's library_album_stats */
    stats: {},
    version: "",
    username: null,
    loaded: false,
    error: "",
});

const tracksCache = new Map(); // album id -> Promise<Track[]>

/** An album's tracks, cached for the session (a record's rows do not
 *  change under the phone). */
export function tracksOf(id) {
    if (!tracksCache.has(id)) {
        tracksCache.set(
            id,
            api.albumTracks(id).catch((e) => { tracksCache.delete(id); throw e; }),
        );
    }
    return tracksCache.get(id);
}

export function albumById(id) {
    return lib.albums.find((a) => a.id === id) || null;
}

/** Newest first — "recently added" everywhere. */
export function newest() {
    return lib.albums.slice().sort((a, b) => b.added_at - a.added_at);
}

/** An artist's records, newest year first. */
export function albumsBy(artist) {
    const k = String(artist || "").toLowerCase();
    return lib.albums
        .filter((a) => a.artist.toLowerCase() === k)
        .sort((x, y) => (y.year || 0) - (x.year || 0) || y.added_at - x.added_at);
}

/** Every artist in the library, biggest first, with the portrait the
 *  library already holds (artist_art_path) when it has one. Casing splits in
 *  the tags ("King Gizzard & The/the Lizard Wizard") merge here. */
export function artists() {
    const m = new Map();
    for (const a of lib.albums) {
        const k = a.artist.toLowerCase();
        let e = m.get(k);
        if (!e) { e = { name: a.artist, albums: 0, tracks: 0, art: null, cover: null }; m.set(k, e); }
        e.albums++;
        e.tracks += a.track_count || 0;
        if (!e.art && a.artist_art_path) e.art = a.artist_art_path;
        if (!e.cover && a.art_path) e.cover = a.art_path;
    }
    return [...m.values()].sort((x, y) => y.albums - x.albums || y.tracks - x.tracks || x.name.localeCompare(y.name));
}

export function isFollowed(name) {
    const k = String(name || "").toLowerCase();
    return lib.follows.some((f) => f.name.toLowerCase() === k);
}
export function followedEntry(name) {
    const k = String(name || "").toLowerCase();
    return lib.follows.find((f) => f.name.toLowerCase() === k) || null;
}
export async function refreshFollows() {
    try { lib.follows = (await api.followedArtists()) || []; } catch { /* keep what we had */ }
}
/** Follow or unfollow, by the catalog identity; the list is re-read. */
export async function toggleFollow(artistId, name, portrait = null) {
    const cur = followedEntry(name);
    if (cur) await api.unfollowArtist(cur.artist_id);
    else await api.followArtist(artistId, name, portrait ?? null);
    await refreshFollows();
}

export async function refreshRecents() {
    try {
        const rows = await api.recentAlbums(14);
        lib.recents = (rows || []).filter((r) => r.kind === "library" && r.album_id != null);
    } catch {
        /* the rail simply stays as it was */
    }
}

/** A download the pipeline just filed, a rescan, an import: the backend
 *  says so (soulseek:library-changed) and the albums are re-read. */
let watching = false;
export async function watchLibrary() {
    if (watching) return;
    watching = true;
    let timer = null;
    try {
        /* two subscriptions that never depended on one another. `listen` is
           an invoke like any other, so one behind the other is two bridge
           round trips at launch for nothing. */
        await Promise.all([
            listen("soulseek:library-changed", () => {
                clearTimeout(timer);
                timer = setTimeout(async () => {
                    try { lib.albums = await api.libraryAlbums(); } catch { /* keep */ }
                    await refreshRecents();
                    void refreshStats();
                }, 600);
            }),
            /* a playlist mutation (the desktop's commands emit it) re-lists them */
            listen("soulseek:playlists-changed", () => { void refreshPlaylists(); }),
        ]);
    } catch { /* not a phone */ }
}

export async function loadLibrary() {
    /* Five reads that never depended on one another. Each is a
       spawn_blocking SQLite read behind the library's single
       `conn: Mutex<Connection>`, so the queries still take their turn —
       what is saved is five bridge round trips collapsing into one.

       Every call keeps the handling it had. The one thing that could have
       moved is `lib.error`, which has two writers and used to be settled
       by the order they were awaited in; the two messages are carried out
       of the round and applied in that same order instead, so a failing
       library still shows the library's message and not app_status's, no
       matter which of them answers last. Nothing is dropped, nothing new
       is asked for, and `lib.loaded` still goes up only once all five
       have settled. */
    const [statusErr, albumsErr, , follows, playlists] = await Promise.all([
        api.appStatus().then((st) => {
            lib.version = st?.version ?? "";
            lib.username = st?.connected_as ?? null;
            return null;
        }, (e) => String(e)),
        api.libraryAlbums().then((rows) => { lib.albums = rows; return null; }, (e) => String(e)),
        refreshRecents(),           // writes lib.recents itself, and swallows its own failure
        api.followedArtists().then((rows) => rows || [], () => []),
        api.listPlaylists().then((rows) => rows || [], () => []),
    ]);
    if (statusErr) lib.error = statusErr;
    if (albumsErr) lib.error = albumsErr;
    lib.follows = follows;
    lib.playlists = playlists;
    lib.loaded = true;
    void refreshStats();
}

/** The files' own aggregates per record — one call for the whole library
 *  (the desktop's RECENTS_FLOOR_SECS, 45, is the floor a play must reach
 *  to count as the last one). */
export async function refreshStats() {
    try {
        const rows = (await api.libraryAlbumStats(45)) || [];
        lib.stats = Object.fromEntries(rows.map((r) => [r.album_id, r]));
    } catch { /* the cards stay quiet */ }
}
/** "FLAC 24/96" for a lossless record, "MP3 320k" for a lossy one. */
export function statLabel(st) {
    if (!st || !st.formats?.length) return "";
    const f = String(st.formats[0]).toUpperCase();
    if (st.bit_depth && st.sample_rate) return f + " " + st.bit_depth + "/" + (st.sample_rate % 1000 === 0 ? st.sample_rate / 1000 : (st.sample_rate / 1000).toFixed(1));
    return st.avg_kbps ? f + " " + st.avg_kbps + "k" : f;
}

export async function refreshPlaylists() {
    try { lib.playlists = (await api.listPlaylists()) || []; } catch { /* keep what we have */ }
}