sanitizeFilename.ts

// it also supports extensions like .tar.gz
export const getFileExtension = (filename: string) =>
  (filename.match(/(\.([^.]*?)(\.([^.]*?))?)(?=\?|#|$)/) || [])[1] ?? "";

//---===---//

/* eslint-disable */
const SANITIZE_FILENAME_REGEXP = {
  NO_LEFT_SPACES: /^\s+/g,
  NO_SEQ_DOTS: /\.+/g,
  ILLEGAL: /[\/\?<>\\:\*\|"]/g,
  CONTROL: /[\x00-\x1f\x80-\x9f]/g,
  RESERVED: /^\.+$/,
  WINDOWS_RESERVED: /^(con|prn|aux|nul|com[0-9]|lpt[0-9])(\..*)?$/i,
  WINDOWS_TRAILING: /[\. ]+$/,
};
/* eslint-enable */

interface SanitizeFilenameOptions {
  replacement?: string;
  maxLength?: number;
}

export const sanitizeFilename = (
  input: string,
  { replacement = "", maxLength = 255 }: SanitizeFilenameOptions = {}
) => {
  if (input.length === 0) {
    throw new Error("The input needs to be defined");
  }

  const {
    NO_LEFT_SPACES,
    NO_SEQ_DOTS,
    ILLEGAL,
    CONTROL,
    RESERVED,
    WINDOWS_RESERVED,
    WINDOWS_TRAILING,
  } = SANITIZE_FILENAME_REGEXP;

  let sanitized = input
    .split("?")[0]
    .split("#")[0]
    .replace(NO_SEQ_DOTS, ".")
    .replace(NO_LEFT_SPACES, replacement)
    .replace(ILLEGAL, replacement)
    .replace(CONTROL, replacement)
    .replace(RESERVED, replacement)
    .replace(WINDOWS_RESERVED, replacement)
    .replace(WINDOWS_TRAILING, replacement);

  if (sanitized.length <= maxLength) {
    return sanitized;
  }

  const fileExtension = getFileExtension(sanitized);
  const fileExtensionLength = fileExtension.length;

  let endIndex = maxLength - 1;
                             
  if (fileExtensionLength === 0) {
    return sanitized.slice(0, endIndex);
  }

  // the latest index is equals to length -1 and we also need to consider the . char before the extension
  endIndex = maxLength - (fileExtensionLength + 2);

  return `${sanitized.slice(0, endIndex)}.${fileExtension}`;
};
                             
export default sanitizeFilename;