// Background DJ-set listening. A scan OUTLIVES the import modal: starting a
// listen closes the modal, progress rides a global chip above the player
// bar, the app stays fully usable, and the finished draft waits on the chip
// until it is reviewed or dismissed. One scan at a time — the backend's
// cancel flag is global by design.
import * as api from "./api.js";

export const setlistScan = $state({
    active: false,
    mode: null, // "youtube" | "file"
    label: "",
    stage: null, // "tool" | "runtime" | "audio" | "decode" | "listen"
    window: 0,
    total: 0,
    pct: null,
    hit: null,
    draft: null, // finished ImportDraft awaiting review
    error: null,
    wantsReview: false, // chip clicked; the Playlists view consumes this
});

let subscribed = false;
function subscribe() {
    if (subscribed) return;
    subscribed = true;
    api.onEvent("playlist:scan-progress", (p) => {
        // A ready chip must not be mutated by stray late events.
        if (!setlistScan.active || setlistScan.draft || !p?.stage) return;
        setlistScan.stage = p.stage;
        if (p.window != null) setlistScan.window = p.window;
        if (p.total != null) setlistScan.total = p.total;
        setlistScan.pct = p.pct ?? null;
        if (p.hit != null) setlistScan.hit = p.hit;
    });
}

async function run(mode, label, call) {
    subscribe();
    Object.assign(setlistScan, {
        active: true,
        mode,
        label,
        stage: mode === "youtube" ? "audio" : "decode",
        window: 0,
        total: 0,
        pct: null,
        hit: null,
        draft: null,
        error: null,
        wantsReview: false,
    });
    try {
        const draft = await call();
        if (draft) {
            setlistScan.draft = draft;
            setlistScan.label = draft.name ?? label;
        } else {
            // Defensive: a null draft must not wedge the chip.
            setlistScan.active = false;
        }
    } catch (e) {
        const message = String(e);
        if (message.includes("canceled")) setlistScan.active = false;
        else setlistScan.error = message;
    }
}

/** Kick a YouTube listen into the background. False = one already runs. */
export function startYoutubeListen(url) {
    if (setlistScan.active) return false;
    void run("youtube", "YouTube set", () => api.playlistScanYoutube(url));
    return true;
}

/** Listen to an already-picked set recording in the background, with an
 *  optionally pasted tracklist riding along. False = one already runs. */
export function startFileListen(path, tracklist = null, label = "Set recording") {
    if (setlistScan.active) return false;
    void run("file", label, () => api.playlistScanFile(path, tracklist));
    return true;
}

/** Hand the finished draft to the review and clear the chip. */
export function takeScanDraft() {
    const draft = setlistScan.draft;
    setlistScan.draft = null;
    setlistScan.active = false;
    setlistScan.wantsReview = false;
    return draft;
}

/** Cancel a running scan, or drop a finished/failed one unseen. */
export function dismissScan() {
    if (setlistScan.active && !setlistScan.draft && !setlistScan.error) {
        void api.playlistScanCancel();
    }
    setlistScan.active = false;
    setlistScan.draft = null;
    setlistScan.error = null;
    setlistScan.wantsReview = false;
}