import { Worker } from 'worker_threads';
import cliProgress from 'cli-progress';

const MAX_THREADS = 10;

export async function saveToc(epub, uploadPath, book_id, author_id) {
    const progressBar = new cliProgress.SingleBar({}, cliProgress.Presets.shades_classic);
    progressBar.start(epub.toc.length, 0);

    let activeWorkers = 0;
    let currentIndex = 0;
    const promises = [];

    function startNextWorker() {
        if (currentIndex >= epub.toc.length) {
            return;
        }

        const elm = epub.toc[currentIndex];
        currentIndex++;
        activeWorkers++;

        const promise = new Promise((resolve, reject) => {
            const worker = new Worker(new URL('./worker.mjs', import.meta.url), {
                workerData: { elm, book_id, author_id }
            });

            worker.on('message', (message) => {
                progressBar.increment();
                activeWorkers--;
                resolve(message);
                startNextWorker();
            });

            worker.on('error', (err) => {
                activeWorkers--;
                reject(err);
                startNextWorker();
            });

            worker.on('exit', (code) => {
                if (code !== 0) {
                    reject(new Error(`Worker stopped with exit code ${code}`));
                }
            });
        });

        promises.push(promise);
    }

    for (let i = 0; i < Math.min(MAX_THREADS, epub.toc.length); i++) {
        startNextWorker();
    }

    await Promise.all(promises);
    progressBar.stop();
}