import { HEIC_DECODE_TIMEOUT_MS, HEIC_MAX_INPUT_BYTES, heicError, heicOutputProfile } from './heicDecodeCore.js';

/** One worker at a time keeps multi-photo selection from multiplying decoder memory. */
export function createHeicDecoder({
  createWorker = () => new Worker(new URL('./heicDecoder.worker.js', import.meta.url), { type: 'module' }),
  timeoutMs = HEIC_DECODE_TIMEOUT_MS,
  setTimeoutFn = setTimeout,
  clearTimeoutFn = clearTimeout,
} = {}) {
  let tail = Promise.resolve();
  const convert = (file, options) => new Promise((resolve, reject) => {
    let worker, settled = false;
    const profile = heicOutputProfile(options);
    const finish = (error, blob = null) => {
      if (settled) return;
      settled = true;
      clearTimeoutFn(timer);
      if (worker) {
        worker.onmessage = null; worker.onerror = null; worker.onmessageerror = null;
        worker.terminate();
      }
      if (error) reject(error); else resolve(blob);
    };
    const timer = setTimeoutFn(() => finish(heicError('HEIC_DECODE_TIMEOUT')), timeoutMs);
    Promise.resolve().then(() => file.arrayBuffer()).then(buffer => {
      if (settled) return;
      if (!(buffer instanceof ArrayBuffer) || !buffer.byteLength || buffer.byteLength > HEIC_MAX_INPUT_BYTES) throw heicError('HEIC_INPUT_TOO_LARGE');
      worker = createWorker();
      worker.onerror = () => finish(heicError('HEIC_DECODE_FAILED'));
      worker.onmessageerror = () => finish(heicError('HEIC_DECODE_FAILED'));
      worker.onmessage = ({ data }) => {
        if (data?.error) return finish(heicError(/^HEIC_[A-Z_]+$/.test(data.error) ? data.error : 'HEIC_DECODE_FAILED'));
        const blob = data?.blob;
        if (!(blob instanceof Blob) || blob.type !== 'image/jpeg' || !blob.size || blob.size > profile.maxSizeBytes) return finish(heicError('HEIC_CONVERSION_FAILED'));
        finish(null, blob);
      };
      worker.postMessage({ buffer, profile }, [buffer]);
    }).catch(error => finish(heicError(error?.code || 'HEIC_DECODE_FAILED')));
  });
  return (file, options = {}) => {
    if (!file || typeof file.arrayBuffer !== 'function' || !Number.isFinite(file.size) || file.size <= 0 || file.size > HEIC_MAX_INPUT_BYTES) {
      return Promise.reject(heicError('HEIC_INPUT_TOO_LARGE'));
    }
    const task = tail.then(() => convert(file, options));
    tail = task.catch(() => {});
    return task;
  };
}

export const decodeHeicToBlob = createHeicDecoder();