/**
 * Personnummer (Swedish personal identity number).
 *
 * The Swedish Personnummer is assigned at birth to all Swedish nationals and to
 * immigrants for tax and identification purposes. The number consists of 10 or
 * 12 digits and starts with the birth date, followed by a serial and a check
 * digit.
 *
 * Source:
 *    https://en.wikipedia.org/wiki/Personal_identity_number_(Sweden)
 *
 * PERSON
 */

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

const ONE_HUNDRED_YEARS_IN_MS = 100 * 365 * 24 * 60 * 60 * 1_000;

function clean(input: string): ReturnType<typeof strings.cleanUnicode> {
  const [value, err] = strings.cleanUnicode(input, ' :');

  if (err) {
    return [value, err];
  }

  const [a, b, c] = strings.splitAt(value, -5, -4);

  return [`${a.replace(/[-+]/g, '')}${b}${c}`, null];
}

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

  let front,
      back,
      sep = '-';

  if (value.length === 12 || value.length === 13) {
    const [yyyy, mm, dd] = strings.splitAt(value, 0, 4, 6, 8);

    const d = buildDate(yyyy, mm, dd);
    if (d === null) {
      // bad date :(
      return value;
    }

    if (new Date().getTime() - d.getTime() > ONE_HUNDRED_YEARS_IN_MS) {
      sep = '+';
    }

    front = `${yyyy.substring(2)}${mm}${dd}`;

    back = value.substring(value.length - 4);
  } else if (value.length === 10) {
    front = value.substring(0, 6);
    back = value.substring(6);
  } else if (value.length === 11) {
    front = value.substring(0, 6);
    sep = value[6];
    back = value.substring(7);
  } else {
    return value;
  }

  return `${front}${sep}${back}`;
}

const impl: Validator = {
  name: 'Swedish Personal Identity Number',
  localName: 'Personnummer',
  compact(input: string): string {
    const [value, err] = clean(input);

    if (err) {
      throw err;
    }

    return value;
  },

  format: formatImpl,

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

    if (error) {
      return { isValid: false, error };
    }
    let a, b, c;
    if (value.length === 11) {
      [a, b, c] = strings.splitAt(value, -5, -4);
    } else if (value.length === 13) {
      [, a, b, c] = strings.splitAt(value, -11, -5, -4);
    } else {
      return { isValid: false, error: new exceptions.InvalidLength() };
    }
    if (!'-+'.includes(b)) {
      return { isValid: false, error: new exceptions.InvalidFormat() };
    }
    const digits = `${a}${c}`;
    if (!strings.isdigits(digits)) {
      return { isValid: false, error: new exceptions.InvalidFormat() };
    }

    let yyyymmdd;
    if (value.length === 13) {
      yyyymmdd = value.substring(0, 8);
    } else {
      const yymmdd = value.substring(0, 6);
      const year = new Date().getFullYear();
      let century = Math.floor(year / 100);

      if (parseInt(yymmdd.substring(0, 2), 10) > year % 100) {
        century -= 1;
      }
      if (b === '+') {
        century -= 1;
      }

      yyyymmdd = `${century}${yymmdd}`;
    }

    // Adjust for coordination numbers ("Samordningsnummer")
    // https://skatteverket.se/servicelankar/otherlanguages/inenglishengelska/individualsandemployees/coordinationnumbers
    const day = parseInt(yyyymmdd.substring(6, 8), 10);
    if (day > 60) {
      yyyymmdd =
          yyyymmdd.substring(0, 6) + (day - 60).toString().padStart(2, '0');
    }

    if (!isValidDateCompactYYYYMMDD(yyyymmdd, true)) {
      return { isValid: false, error: new exceptions.InvalidComponent() };
    }

    if (!luhnChecksumValidate(digits)) {
      return { isValid: false, error: new exceptions.InvalidChecksum() };
    }

    return {
      isValid: true,
      compact: formatImpl(input),
      isIndividual: true,
      isCompany: false,
    };
  },
};

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