/**
 * FPA, ΦΠΑ, ΑΦΜ (Αριθμός Φορολογικού Μητρώου, the Greek VAT number).
 *
 * The FPA is a 9-digit number with a simple checksum.
 *
 * ENTITY
 */

import * as exceptions from '../exceptions';
import { strings } from '../util';
import { Validator, ValidateReturn } from '../types';

function clean(input: string): ReturnType<typeof strings.cleanUnicode> {
  const [value, err] = strings.cleanUnicode(input, ' ');
  if (err !== null) {
    return [value, err];
  }
  let num = value;
  if (value.startsWith('GR') || value.startsWith('EL')) {
    num = value.substr(2);
  }

  // Old format was 8 digits
  if (num.length === 8) {
    return [`0${num}`, null];
  }
  return [num, null];
}

const impl: Validator = {
  name: 'Greek VAT Number',
  localName: 'Αριθμός Φορολογικού Μητρώου',
  abbreviation: 'ΑΦΜ',
  compact(input: string): string {
    const [value, err] = clean(input);

    if (err) {
      throw err;
    }

    return value;
  },

  format(input: string): string {
    const [value] = clean(input);

    return value;
  },

  validate(input: string): ValidateReturn {
    const [value, error] = clean(input);

    if (error) {
      return { isValid: false, error };
    }
    if (value.length !== 9) {
      return { isValid: false, error: new exceptions.InvalidLength() };
    }
    if (!strings.isdigits(value)) {
      return { isValid: false, error: new exceptions.InvalidFormat() };
    }

    const [front, check] = strings.splitAt(value, -1);

    const sum = front
      .split('')
      .map(v => parseInt(v, 10))
      .reduce((acc, v) => acc * 2 + v, 0);

    if (String(((sum * 2) % 11) % 10) !== check) {
      return { isValid: false, error: new exceptions.InvalidChecksum() };
    }

    return {
      isValid: true,
      compact: value,
      isIndividual: false,
      isCompany: true,
    };
  },
};

export const { name, localName, abbreviation, validate, format, compact } =
  impl;