/**
 * In the past, name of `typia` was `typescript-json`, and supported
 * JSON serialization by wrapping `fast-json-stringify. `typescript-json` was
 * a helper library of `fast-json-stringify`, which can skip manual JSON schema
 * definition just by putting pure TypeScript type.
 *
 * This `$string` function is a part of `fast-json-stringify` at that time, and
 * still being used in `typia` for the string serialization.
 *
 * @reference https://github.com/fastify/fast-json-stringify/blob/master/lib/serializer.js
 * @blog https://dev.to/samchon/good-bye-typescript-is-ancestor-of-typia-20000x-faster-validator-49fi
 */
export const _jsonStringifyString = (str: string): string => {
  const len = str.length;
  let result = "";
  let last = -1;
  let point = 255;

  // eslint-disable-next-line
  for (var i = 0; i < len; i++) {
    point = str.charCodeAt(i);
    if (point < 32) {
      return JSON.stringify(str);
    }
    if (point >= 0xd800 && point <= 0xdfff) {
      // The current character is a surrogate.
      return JSON.stringify(str);
    }
    if (
      point === 0x22 || // '"'
      point === 0x5c // '\'
    ) {
      last === -1 && (last = 0);
      result += str.slice(last, i) + "\\";
      last = i;
    }
  }

  return (
    (last === -1 && '"' + str + '"') || '"' + result + str.slice(last) + '"'
  );
};