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feat: add removeTrailingDecimalZeros function and related tests #252

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1 change: 1 addition & 0 deletions src/exports.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@ const expectedNamedExports = [
'extractGetAgConfig',
'getAmountWithTax',
'getTaxValue',
'removeTrailingDecimalZeros',
];

/**
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1 change: 1 addition & 0 deletions src/index.ts
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Expand Up @@ -4,6 +4,7 @@ export {
formatAmountFromString,
formatPriceUnit,
parseDecimalValue,
removeTrailingDecimalZeros,
toIntegerAmount,
addSeparatorToDineroString,
} from './money/formatters';
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123 changes: 123 additions & 0 deletions src/money/formatters.test.ts
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Expand Up @@ -6,6 +6,7 @@ import {
formatAmountFromString,
formatPriceUnit,
parseDecimalValue,
removeTrailingDecimalZeros,
toIntegerAmount,
unitDisplayLabels,
} from './formatters';
Expand Down Expand Up @@ -308,3 +309,125 @@ describe('parseDecimalValue', () => {
expect(parseDecimalValue(value)).toEqual(expected);
});
});

describe('removeTrailingDoubleDecimalZeros', () => {
describe('with dot decimal separator', () => {
it.each`
input | expected
${'10.00'} | ${'10'}
${'10.50'} | ${'10.50'}
${'10.0000'} | ${'10'}
${'10.1000'} | ${'10.10'}
${'10.1200'} | ${'10.12'}
${'10.0500'} | ${'10.05'}
${'0.500'} | ${'0.50'}
${'0.00'} | ${'0'}
${'123.4500'} | ${'123.45'}
${'999.9900'} | ${'999.99'}
${'1.000000'} | ${'1'}
`('should remove trailing double zeros from $input to get $expected', ({ input, expected }) => {
expect(removeTrailingDecimalZeros(input)).toBe(expected);
});
});

describe('with comma decimal separator', () => {
it.each`
input | expected
${'10,00'} | ${'10'}
${'10,50'} | ${'10,50'}
${'10,0000'} | ${'10'}
${'10,1000'} | ${'10,10'}
${'10,1200'} | ${'10,12'}
${'10,0500'} | ${'10,05'}
${'0,500'} | ${'0,50'}
${'0,00'} | ${'0'}
${'123,4500'} | ${'123,45'}
${'999,9900'} | ${'999,99'}
${'1,000000'} | ${'1'}
`('should remove trailing double zeros from $input to get $expected', ({ input, expected }) => {
expect(removeTrailingDecimalZeros(input)).toBe(expected);
});
});

describe('with currency symbols and units', () => {
it.each`
input | expected
${'10.00 €'} | ${'10 €'}
${'10.00 €/Stück'} | ${'10 €/Stück'}
${'10.1200 USD'} | ${'10.12 USD'}
${'0.00 €/kWh'} | ${'0 €/kWh'}
${'123.4500 CHF/month'} | ${'123.45 CHF/month'}
${'10,00 €'} | ${'10 €'}
${'10,00€/Stück'} | ${'10€/Stück'}
${'10,1200 USD'} | ${'10,12 USD'}
${'0,00 €/kWh'} | ${'0 €/kWh'}
${'123,4500 CHF/month'} | ${'123,45 CHF/month'}
`('should remove trailing double zeros from $input with suffix to get $expected', ({ input, expected }) => {
expect(removeTrailingDecimalZeros(input)).toBe(expected);
});
});

describe('with complex suffixes', () => {
it.each`
input | expected
${'10.00 €/Stück pro Monat'} | ${'10 €/Stück pro Monat'}
${'15.0000/unit'} | ${'15/unit'}
${'25.1200 per item'} | ${'25.12 per item'}
${'100.00€'} | ${'100€'}
${'50.0000$'} | ${'50$'}
${'10,00 €/Stück pro Monat'} | ${'10 €/Stück pro Monat'}
${'15,0000/unit'} | ${'15/unit'}
${'25,1200 per item'} | ${'25,12 per item'}
${'100,00€'} | ${'100€'}
${'50,0000$'} | ${'50$'}
`('should handle complex suffixes correctly for $input', ({ input, expected }) => {
expect(removeTrailingDecimalZeros(input)).toBe(expected);
});
});

describe('edge cases', () => {
it.each`
input | expected | description
${'10.01'} | ${'10.01'} | ${'should not modify numbers without trailing double zeros'}
${'10.10'} | ${'10.10'} | ${'should not modify single trailing zero'}
${'10'} | ${'10'} | ${'should not modify integers without decimals'}
${'10.'} | ${'10.'} | ${'should not modify numbers ending with decimal separator only'}
${'10.0'} | ${'10'} | ${'should not modify single decimal zero'}
${'abc'} | ${'abc'} | ${'should not modify non-numeric strings'}
${'10.00.00'} | ${'10.00.00'} | ${'should not modify invalid number formats'}
${''} | ${''} | ${'should handle empty strings'}
${'10.000000000'} | ${'10'} | ${'should remove multiple consecutive double zeros'}
${'10,01'} | ${'10,01'} | ${'should not modify numbers without trailing double zeros (comma)'}
${'10,10'} | ${'10,10'} | ${'should not modify single trailing zero (comma)'}
${'10,0'} | ${'10'} | ${'should not modify single decimal zero (comma)'}
`('$description: $input -> $expected', ({ input, expected }) => {
expect(removeTrailingDecimalZeros(input)).toBe(expected);
});
});

describe('preserves whitespace and formatting', () => {
it.each`
input | expected
${'10.00 €'} | ${'10 €'}
${'10.00\t€'} | ${'10\t€'}
${'10.00\n€/unit'} | ${'10\n€/unit'}
${'10,00 €'} | ${'10 €'}
${'10,00\t€'} | ${'10\t€'}
${'10,00\n€/unit'} | ${'10\n€/unit'}
`('should preserve whitespace in $input', ({ input, expected }) => {
expect(removeTrailingDecimalZeros(input)).toBe(expected);
});
});

describe('with minDecimals', () => {
it.each`
input | expected | minDecimals
${'10.1000'} | ${'10.1'} | ${0}
${'10.1000'} | ${'10.10'} | ${2}
${'10.1000'} | ${'10.100'} | ${3}
${'10.1000'} | ${'10.1000'} | ${4}
`('should remove trailing double zeros from $input to get $expected', ({ input, expected, minDecimals }) => {
expect(removeTrailingDecimalZeros(input, minDecimals)).toBe(expected);
});
});
});
46 changes: 46 additions & 0 deletions src/money/formatters.ts
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Expand Up @@ -282,6 +282,52 @@ export const unitDisplayLabels = {
kwp: 'kWp',
} as const;

/**
* Removes trailing double-zero groups from the decimal part of a formatted decimal amount string.
*
* - Always preserves any suffixes after the number (whitespace, newlines, currency symbols, unit names, etc.).
* - Removes the entire decimal part if all digits after the separator are zeros.
* - Keeps at least `minDecimals` decimal digits when a fractional part remains after trimming.
* - Handles both dot `.` and comma `,` as decimal separators.
*
* @param decimalAmount - The decimal amount to remove trailing zeros from.
* @param minDecimals - The minimum number of decimal digits to keep.
* @returns The decimal amount with trailing zeros removed.
*/
export const removeTrailingDecimalZeros = (decimalAmount: string, minDecimals = 2): string => {
if (decimalAmount.split(/[.,]/).length > 2) return decimalAmount;

const match = decimalAmount.match(/^(-?\d+)([.,])(\d+)(.*)$/s);
if (!match) return decimalAmount;

const [, intPart, sep, decimals, suffix] = match;

// Remove trailing double-zero pairs
let trimmed = decimals.replace(/(00)+$/, '');
const removedDoubleZeros = decimals !== trimmed;

// If nothing remains, or all remaining decimals are zeros, remove decimal entirely
if (trimmed === '' || /^0+$/.test(trimmed)) {
return intPart + suffix; // preserve suffix (spaces, newlines, currency)
}

// If minDecimals is 0, we can remove trailing single zeros as well
if (minDecimals === 0) {
trimmed = trimmed.replace(/0+$/, '');
// If all decimals were removed, don't include the decimal separator
if (trimmed === '') {
return intPart + suffix;
}
}

// Pad to minDecimals only if we removed double zeros and minDecimals > 0
if (removedDoubleZeros && minDecimals > 0 && trimmed.length < minDecimals) {
trimmed = trimmed.padEnd(minDecimals, '0');
}

return `${intPart}${sep}${trimmed}${suffix}`; // always append suffix
};

/**
* Formats built-in price units into a displayable representation. Eg. kw -> kW
*
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