import crypto from 'node:crypto';

export function createImgproxySigner(key, salt) {
  const keyBuf = Buffer.from(key, 'hex');
  const saltBuf = Buffer.from(salt, 'hex');

  function signPath(path) {
    const signaturePayload = Buffer.concat([saltBuf, Buffer.from(path)]);
    const signature = crypto.createHmac('sha256', keyBuf).update(signaturePayload).digest();
    const signatureB64 = signature.toString('base64url');
    return `/${signatureB64}${path}`;
  }

  function buildUrl(baseUrl, storagePath, preset = 'display') {
    if (!baseUrl || !storagePath) {
      throw new Error('baseUrl and storagePath are required');
    }

    let width, height, quality, format;
    switch (preset) {
      case 'vision':
        width = 768;
        height = 768;
        quality = 60;
        format = 'jpg';
        break;
      case 'thumb':
        width = 256;
        height = 256;
        quality = 70;
        format = 'jpg';
        break;
      case 'display':
      default:
        width = 1280;
        height = 1280;
        quality = 85;
        format = 'jpg';
        break;
    }

    const unsignedPath = `/rs:fit:${width}:${height}:0/q:${quality}/plain/local:///${storagePath}@${format}`;
    const signedPath = signPath(unsignedPath);

    const baseUrlNormalized = String(baseUrl).replace(/\/$/, '');
    return `${baseUrlNormalized}${signedPath}`;
  }

  return { buildUrl, signPath };
}

export default createImgproxySigner;