PANValidator constructor

PANValidator()

validate the PAN.

According the WIKI https://en.wikipedia.org/wiki/Permanent_account_number

The PAN (or PAN number) is a ten-character long alpha-numeric unique identifier.

The PAN structure is as follows: Fourth character P — Individual or Person Example: AAAPZ1234C

1. The first five characters are letters (in uppercase by default), followed by four numerals, and the last (tenth) character is a letter.
2. The first three characters of the code are three letters forming a sequence of alphabets letters from AAA to ZZZ
3. The fourth character identifies the type of holder of the card. Each holder type is uniquely defined by a letter from the list below: A — Association of persons (AOP) B — Body of individuals (BOI) C — Company F — Firm G — Government H — HUF (Hindu undivided family) L — Local authority J — Artificial juridical person P — Person (Individual) T — Trust (AOP)
4. The fifth character of the PAN is the first character of either: a. of the surname or last name of the person, in the case of a "personal" PAN card, where the fourth character is "P" or b. of the name of the entity, trust, society, or organisation in the case of a company/HUF/firm/AOP/trust/BOI/local authority/artificial judicial person/government, where the fourth character is "C", "H", "F", "A", "T", "B", "L", "J", "G".
5. The last (tenth) character is an alphabetic digit used as a check-sum to verify the validity of that current code.

Implementation

factory PANValidator() {
  _instance ??= PANValidator._();
  return _instance!;
}