ksv741
e6f58ef0ee
Store exact RUB balances, atomic transfers, linked refunds and versioned edits independently of T-Bank. Add migration, HTTP and durability verification.
63 lines
2.3 KiB
TypeScript
63 lines
2.3 KiB
TypeScript
export type Decimal = { value: bigint; scale: number };
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export function decimalFromString(value: string): Decimal {
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if (!/^-?(?:0|[1-9]\d*)(?:\.\d+)?$/.test(value))
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throw new Error('Invalid decimal string');
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const negative = value.startsWith('-');
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const [whole, fraction = ''] = (negative ? value.slice(1) : value).split('.');
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return {
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value: (negative ? -1n : 1n) * BigInt(`${whole}${fraction}`),
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scale: fraction.length,
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};
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}
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export function add(left: Decimal, right: Decimal): Decimal {
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const scale = Math.max(left.scale, right.scale);
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return {
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value:
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left.value * 10n ** BigInt(scale - left.scale) +
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right.value * 10n ** BigInt(scale - right.scale),
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scale,
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};
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}
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export function subtract(left: Decimal, right: Decimal): Decimal {
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return add(left, { value: -right.value, scale: right.scale });
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}
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export function multiply(left: Decimal, right: Decimal): Decimal {
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return { value: left.value * right.value, scale: left.scale + right.scale };
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}
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export function isZero(value: Decimal): boolean {
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return value.value === 0n;
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}
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export function compare(left: Decimal, right: Decimal): number {
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const difference = subtract(left, right).value;
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return difference === 0n ? 0 : difference > 0n ? 1 : -1;
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}
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export function formatDecimal({ value, scale }: Decimal): string {
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if (value === 0n) return '0';
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const sign = value < 0n ? '-' : '';
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if (scale === 0) return `${sign}${value < 0n ? -value : value}`;
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const digits = (value < 0n ? -value : value)
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.toString()
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.padStart(scale + 1, '0');
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const whole = digits.slice(0, -scale) || '0';
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const fraction = digits.slice(-scale).replace(/0+$/, '');
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return `${sign}${whole}${fraction ? `.${fraction}` : ''}`;
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}
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// Round half away from zero; callers choose presentation precision explicitly.
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export function divide(left: Decimal, right: Decimal, scale: number): Decimal {
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if (right.value === 0n) throw new Error('Division by zero');
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const numerator = left.value * 10n ** BigInt(right.scale + scale);
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const denominator = right.value * 10n ** BigInt(left.scale);
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const sign = numerator < 0n !== denominator < 0n ? -1n : 1n;
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const n = numerator < 0n ? -numerator : numerator;
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const d = denominator < 0n ? -denominator : denominator;
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return { value: sign * ((n + d / 2n) / d), scale };
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}
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