einvoice/test/test.decimal.ts

import { expect, tap } from '@git.zone/tstest/tapbundle';
import { Decimal, decimal, RoundingMode } from '../ts/formats/utils/decimal.js';

tap.test('Decimal - basic construction', async () => {
  // From string
  const d1 = new Decimal('123.456');
  expect(d1.toString()).toEqual('123.456');
  
  // From number
  const d2 = new Decimal(123.456);
  expect(d2.toString()).toEqual('123.456');
  
  // From bigint
  const d3 = new Decimal(123n);
  expect(d3.toString()).toEqual('123');
  
  // From another Decimal
  const d4 = new Decimal(d1);
  expect(d4.toString()).toEqual('123.456');
  
  // Negative values
  const d5 = new Decimal('-123.456');
  expect(d5.toString()).toEqual('-123.456');
});

tap.test('Decimal - arithmetic operations', async () => {
  const a = new Decimal('10.50');
  const b = new Decimal('3.25');
  
  // Addition
  expect(a.add(b).toString()).toEqual('13.75');
  
  // Subtraction
  expect(a.subtract(b).toString()).toEqual('7.25');
  
  // Multiplication
  expect(a.multiply(b).toString()).toEqual('34.125');
  
  // Division
  expect(a.divide(b).toString()).toEqual('3.2307692307');
  
  // Percentage
  const amount = new Decimal('100');
  const rate = new Decimal('19');
  expect(amount.percentage(rate).toString()).toEqual('19');
});

tap.test('Decimal - rounding modes', async () => {
  // HALF_UP (default)
  expect(new Decimal('2.5').round(0, 'HALF_UP').toString()).toEqual('3');
  expect(new Decimal('2.4').round(0, 'HALF_UP').toString()).toEqual('2');
  expect(new Decimal('-2.5').round(0, 'HALF_UP').toString()).toEqual('-3');
  
  // HALF_DOWN
  expect(new Decimal('2.5').round(0, 'HALF_DOWN').toString()).toEqual('2');
  expect(new Decimal('2.6').round(0, 'HALF_DOWN').toString()).toEqual('3');
  expect(new Decimal('-2.5').round(0, 'HALF_DOWN').toString()).toEqual('-2');
  
  // HALF_EVEN (Banker's rounding)
  expect(new Decimal('2.5').round(0, 'HALF_EVEN').toString()).toEqual('2');
  expect(new Decimal('3.5').round(0, 'HALF_EVEN').toString()).toEqual('4');
  expect(new Decimal('2.4').round(0, 'HALF_EVEN').toString()).toEqual('2');
  expect(new Decimal('2.6').round(0, 'HALF_EVEN').toString()).toEqual('3');
  
  // UP (away from zero)
  expect(new Decimal('2.1').round(0, 'UP').toString()).toEqual('3');
  expect(new Decimal('-2.1').round(0, 'UP').toString()).toEqual('-3');
  
  // DOWN (toward zero)
  expect(new Decimal('2.9').round(0, 'DOWN').toString()).toEqual('2');
  expect(new Decimal('-2.9').round(0, 'DOWN').toString()).toEqual('-2');
  
  // CEILING (toward positive infinity)
  expect(new Decimal('2.1').round(0, 'CEILING').toString()).toEqual('3');
  expect(new Decimal('-2.9').round(0, 'CEILING').toString()).toEqual('-2');
  
  // FLOOR (toward negative infinity)
  expect(new Decimal('2.9').round(0, 'FLOOR').toString()).toEqual('2');
  expect(new Decimal('-2.1').round(0, 'FLOOR').toString()).toEqual('-3');
});

tap.test('Decimal - EN16931 calculation scenarios', async () => {
  // Line item calculation
  const quantity = new Decimal('3');
  const unitPrice = new Decimal('33.333333');
  const lineTotal = quantity.multiply(unitPrice);
  expect(lineTotal.round(2).toString()).toEqual('100');
  
  // VAT calculation
  const netAmount = new Decimal('100');
  const vatRate = new Decimal('19');
  const vatAmount = netAmount.percentage(vatRate);
  expect(vatAmount.toString()).toEqual('19');
  
  // Total with VAT
  const grossAmount = netAmount.add(vatAmount);
  expect(grossAmount.toString()).toEqual('119');
  
  // Complex calculation with allowances
  const lineExtension = new Decimal('150.00');
  const allowance = new Decimal('10.00');
  const charge = new Decimal('5.00');
  const taxExclusive = lineExtension.subtract(allowance).add(charge);
  expect(taxExclusive.toString()).toEqual('145');
  
  const vat = taxExclusive.percentage(new Decimal('19'));
  expect(vat.round(2).toString()).toEqual('27.55');
  
  const total = taxExclusive.add(vat);
  expect(total.round(2).toString()).toEqual('172.55');
});

tap.test('Decimal - comparisons', async () => {
  const a = new Decimal('10.50');
  const b = new Decimal('10.50');
  const c = new Decimal('10.51');
  
  // Equality
  expect(a.equals(b)).toBeTrue();
  expect(a.equals(c)).toBeFalse();
  
  // With tolerance
  expect(a.equals(c, '0.01')).toBeTrue();
  expect(a.equals(c, '0.005')).toBeFalse();
  
  // Comparisons
  expect(a.lessThan(c)).toBeTrue();
  expect(c.greaterThan(a)).toBeTrue();
  expect(a.lessThanOrEqual(b)).toBeTrue();
  expect(a.greaterThanOrEqual(b)).toBeTrue();
});

tap.test('Decimal - edge cases', async () => {
  // Very small numbers
  const tiny = new Decimal('0.0000000001');
  expect(tiny.multiply(new Decimal('1000000000')).toString()).toEqual('0.1');
  
  // Very large numbers
  const huge = new Decimal('999999999999999999');
  expect(huge.add(new Decimal('1')).toString()).toEqual('1000000000000000000');
  
  // Division by zero
  const zero = new Decimal('0');
  const one = new Decimal('1');
  let errorThrown = false;
  try {
    one.divide(zero);
  } catch (e) {
    errorThrown = true;
    expect(e.message).toEqual('Division by zero');
  }
  expect(errorThrown).toBeTrue();
  
  // Zero operations
  expect(zero.add(one).toString()).toEqual('1');
  expect(zero.multiply(one).toString()).toEqual('0');
  expect(zero.isZero()).toBeTrue();
  expect(one.isZero()).toBeFalse();
});

tap.test('Decimal - currency calculations with different minor units', async () => {
  // EUR (2 decimal places)
  const eurAmount = new Decimal('100.00');
  const eurVat = eurAmount.percentage(new Decimal('19'));
  expect(eurVat.round(2).toString()).toEqual('19');
  
  // JPY (0 decimal places)
  const jpyAmount = new Decimal('1000');
  const jpyTax = jpyAmount.percentage(new Decimal('10'));
  expect(jpyTax.round(0).toString()).toEqual('100');
  
  // KWD (3 decimal places)
  const kwdAmount = new Decimal('100.000');
  const kwdTax = kwdAmount.percentage(new Decimal('5'));
  expect(kwdTax.round(3).toString()).toEqual('5');
  
  // BTC (8 decimal places for satoshis)
  const btcAmount = new Decimal('0.00100000');
  const btcFee = btcAmount.percentage(new Decimal('0.1'));
  expect(btcFee.round(8).toString()).toEqual('0.000001');
});

tap.test('Decimal - static methods', async () => {
  // Sum
  const values = ['10.50', '20.25', '30.75'];
  const sum = Decimal.sum(values);
  expect(sum.toString()).toEqual('61.5');
  
  // Min
  const min = Decimal.min('10.50', '20.25', '5.75');
  expect(min.toString()).toEqual('5.75');
  
  // Max
  const max = Decimal.max('10.50', '20.25', '5.75');
  expect(max.toString()).toEqual('20.25');
  
  // From percentage
  const rate = Decimal.fromPercentage('19%');
  expect(rate.toString()).toEqual('0.19');
});

tap.test('Decimal - formatting', async () => {
  const value = new Decimal('1234.567890');
  
  // Fixed decimal places
  expect(value.toFixed(2)).toEqual('1234.57');
  expect(value.toFixed(0)).toEqual('1235');
  expect(value.toFixed(4)).toEqual('1234.5679');
  
  // toString with decimal places
  expect(value.toString(2)).toEqual('1234.56');
  expect(value.toString(6)).toEqual('1234.567890');
  
  // Automatic trailing zero removal
  const rounded = new Decimal('100.00');
  expect(rounded.toString()).toEqual('100');
  expect(rounded.toFixed(2)).toEqual('100.00');
});

tap.test('Decimal - real-world invoice calculation', async () => {
  // Invoice with multiple lines and VAT rates
  const lines = [
    { quantity: '2', unitPrice: '50.00', vatRate: '19' },
    { quantity: '3', unitPrice: '33.33', vatRate: '19' },
    { quantity: '1', unitPrice: '100.00', vatRate: '7' }
  ];
  
  let totalNet = Decimal.ZERO;
  let totalVat19 = Decimal.ZERO;
  let totalVat7 = Decimal.ZERO;
  
  for (const line of lines) {
    const quantity = new Decimal(line.quantity);
    const unitPrice = new Decimal(line.unitPrice);
    const lineNet = quantity.multiply(unitPrice);
    totalNet = totalNet.add(lineNet);
    
    const vatAmount = lineNet.percentage(new Decimal(line.vatRate));
    if (line.vatRate === '19') {
      totalVat19 = totalVat19.add(vatAmount);
    } else {
      totalVat7 = totalVat7.add(vatAmount);
    }
  }
  
  expect(totalNet.round(2).toString()).toEqual('299.99');
  expect(totalVat19.round(2).toString()).toEqual('38');
  expect(totalVat7.round(2).toString()).toEqual('7');
  
  const totalVat = totalVat19.add(totalVat7);
  const totalGross = totalNet.add(totalVat);
  
  expect(totalVat.round(2).toString()).toEqual('45');
  expect(totalGross.round(2).toString()).toEqual('344.99');
});

export default tap.start();