import { childLogger } from "./logger.js";
const log = childLogger("mutex");
let locked = false;
let holder = "";
const queue = [];
/**
 * Maximum time to wait for the TDLib mutex (ms).
 * If the mutex is not available within this time, the operation is rejected.
 * Default: 30 minutes (long enough for large downloads, short enough to detect hangs).
 */
const MUTEX_WAIT_TIMEOUT_MS = 30 * 60 * 1000;
/**
 * Ensures only one TDLib client runs at a time across the entire worker process.
 * Both the scheduler (auth, ingestion) and the fetch listener acquire this
 * before creating any TDLib client.
 *
 * Includes a wait timeout to prevent indefinite blocking if the current holder hangs.
 */
export async function withTdlibMutex(label, fn) {
    if (locked) {
        log.info({ waiting: label, holder }, "Waiting for TDLib mutex");
        await new Promise((resolve, reject) => {
            const entry = { resolve, reject, label };
            queue.push(entry);
            // Timeout: reject if we've been waiting too long
            const timer = setTimeout(() => {
                const idx = queue.indexOf(entry);
                if (idx !== -1) {
                    queue.splice(idx, 1);
                    reject(new Error(`TDLib mutex wait timeout after ${MUTEX_WAIT_TIMEOUT_MS / 60_000}min ` +
                        `(waiting: ${label}, holder: ${holder})`));
                }
            }, MUTEX_WAIT_TIMEOUT_MS);
            // Wrap resolve to clear the timer
            const origResolve = entry.resolve;
            entry.resolve = () => {
                clearTimeout(timer);
                origResolve();
            };
        });
    }
    locked = true;
    holder = label;
    log.debug({ label }, "TDLib mutex acquired");
    try {
        return await fn();
    }
    finally {
        locked = false;
        holder = "";
        const next = queue.shift();
        if (next) {
            log.debug({ next: next.label }, "TDLib mutex releasing to next waiter");
            next.resolve();
        }
        else {
            log.debug({ label }, "TDLib mutex released");
        }
    }
}
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