const isEmoji = /[\ud800-\udbff][\udc00-\udfff]/g;
const isEmojiCode = /\[:\d+]/g;

export const emojiToString = (str: string) => {
  const result = str.replace(isEmoji, (char) => {
    let H;
    let L;
    let code;
    let s;

    if (char.length === 2) {
      H = char.charCodeAt(0);
      L = char.charCodeAt(1);
      code = (H - 0xd800) * 0x400 + 0x10000 + L - 0xdc00;
      s = `[:${code}]`;
    } else {
      s = char;
    }

    return s;
  });

  return result;
};

export const stringToEmoji = (strObj: string) => {
  if (!isEmojiCode.test(strObj)) {
    return strObj;
  }

  const arr = strObj.match(isEmojiCode) || [];
  let result = strObj;

  let H;
  let L;
  let code;

  arr.forEach((item) => {
    code = item;
    code = Number(code.replace('[:', '').replace(']', ''));
    H = Math.floor((code - 0x10000) / 0x400) + 0xd800;
    L = ((code - 0x10000) % 0x400) + 0xdc00;
    code = `[:${code}]`;
    const s = String.fromCharCode(H, L);
    result = result.replace(code, s);
  });

  return result;
};