export async function readRequestBody(req, limitBytes) {
  const chunks = [];
  let size = 0;

  for await (const chunk of req) {
    size += chunk.length;
    if (size > limitBytes) {
      const error = new Error('Request body is too large');
      error.status = 413;
      throw error;
    }
    chunks.push(chunk);
  }

  return Buffer.concat(chunks);
}

export function parseMultipart(buffer, contentType) {
  const match = /boundary=(?:"([^"]+)"|([^;]+))/i.exec(contentType || '');
  if (!match) {
    const error = new Error('Missing multipart boundary');
    error.status = 400;
    throw error;
  }

  const boundary = `--${match[1] || match[2]}`;
  const binary = buffer.toString('binary');
  const parts = [];

  for (const raw of binary.split(boundary)) {
    if (!raw || raw === '--\r\n' || raw === '--') {
      continue;
    }

    const trimmed = raw.replace(/^\r\n/, '').replace(/\r\n--$/, '');
    const separator = trimmed.indexOf('\r\n\r\n');
    if (separator === -1) {
      continue;
    }

    const headerText = trimmed.slice(0, separator);
    let bodyText = trimmed.slice(separator + 4);
    if (bodyText.endsWith('\r\n')) {
      bodyText = bodyText.slice(0, -2);
    }

    const disposition = /content-disposition:\s*form-data;\s*([^\r\n]+)/i.exec(headerText)?.[1] || '';
    const name = /name="([^"]+)"/i.exec(disposition)?.[1] || '';
    const filename = /filename="([^"]*)"/i.exec(disposition)?.[1] || '';

    parts.push({
      name,
      filename,
      data: Buffer.from(bodyText, 'binary')
    });
  }

  return parts;
}