import { FFmpeg } from '@ffmpeg/ffmpeg';
import { toBlobURL } from '@ffmpeg/util';

let ffmpeg = null;
let loadingPromise = null;

async function loadFFmpeg() {
    if (loadingPromise) return loadingPromise;

    loadingPromise = (async () => {
        ffmpeg = new FFmpeg();

        ffmpeg.on('log', ({ message }) => {
            self.postMessage({ type: 'log', message });
        });

        ffmpeg.on('progress', ({ progress, time }) => {
            self.postMessage({
                type: 'progress',
                stage: 'encoding',
                progress: progress * 100,
                time,
            });
        });

        self.postMessage({ type: 'progress', stage: 'loading', message: 'Loading FFmpeg...' });

        const baseURL = 'https://unpkg.com/@ffmpeg/core@0.12.6/dist/esm';
        await ffmpeg.load({
            coreURL: await toBlobURL(`${baseURL}/ffmpeg-core.js`, 'text/javascript'),
            wasmURL: await toBlobURL(`${baseURL}/ffmpeg-core.wasm`, 'application/wasm'),
        });
    })();

    return loadingPromise;
}

self.onmessage = async (e) => {
    const { audioData } = e.data;

    try {
        await loadFFmpeg();

        self.postMessage({ type: 'progress', stage: 'encoding', message: 'Encoding to MP3 320kbps...' });

        try {
            // Write input file to FFmpeg virtual filesystem
            await ffmpeg.writeFile('input', new Uint8Array(audioData));

            // Encode to MP3 with 320kbps CBR, strip source metadata to avoid duplicate ID3 tags
            await ffmpeg.exec([
                '-i',
                'input',
                '-map_metadata',
                '-1',
                '-c:a',
                'libmp3lame',
                '-b:a',
                '320k',
                '-ar',
                '44100',
                'output.mp3',
            ]);

            self.postMessage({ type: 'progress', stage: 'finalizing', message: 'Finalizing MP3...' });

            // Read output file - use Uint8Array directly to avoid extra bytes from ArrayBuffer
            const data = await ffmpeg.readFile('output.mp3');
            const mp3Blob = new Blob([data], { type: 'audio/mpeg' });

            self.postMessage({ type: 'complete', blob: mp3Blob });
        } finally {
            // Always cleanup virtual filesystem files
            try {
                await ffmpeg.deleteFile('input');
            } catch {
                // File may not exist if writeFile failed
            }
            try {
                await ffmpeg.deleteFile('output.mp3');
            } catch {
                // File may not exist if exec failed
            }
        }
    } catch (error) {
        self.postMessage({ type: 'error', message: error.message });
    }
};