diff --git a/packages/taler-util/src/amounts.test.ts b/packages/taler-util/src/amounts.test.ts index 064023e2d..644b8bdb4 100644 --- a/packages/taler-util/src/amounts.test.ts +++ b/packages/taler-util/src/amounts.test.ts @@ -138,3 +138,13 @@ test("amount multiplication", (t) => { t.is(Amounts.stringify(Amounts.mult(sAmt("EUR:1.11"), 4).amount), "EUR:4.44"); t.is(Amounts.stringify(Amounts.mult(sAmt("EUR:1.11"), 5).amount), "EUR:5.55"); }); + + + +test("amount division", (t) => { + t.is(Amounts.divmod("EUR:5", "EUR:1").quotient, 5); + t.is(Amounts.stringify(Amounts.divmod("EUR:5", "EUR:1").remainder), "EUR:0"); + + t.is(Amounts.divmod("EUR:5", "EUR:2").quotient, 2); + t.is(Amounts.stringify(Amounts.divmod("EUR:5", "EUR:2").remainder), "EUR:1"); +}); diff --git a/packages/taler-util/src/amounts.ts b/packages/taler-util/src/amounts.ts index d4e798030..a998c8f63 100644 --- a/packages/taler-util/src/amounts.ts +++ b/packages/taler-util/src/amounts.ts @@ -95,6 +95,11 @@ export interface Result { */ export type AmountLike = AmountString | AmountJson; +export interface DivmodResult { + quotient: number; + remainder: AmountJson; +} + /** * Helper class for dealing with amounts. */ @@ -135,6 +140,29 @@ export class Amounts { return amt; } + static divmod(a1: AmountLike, a2: AmountLike): DivmodResult { + const am1 = Amounts.jsonifyAmount(a1); + const am2 = Amounts.jsonifyAmount(a2); + if (am1.currency != am2.currency) { + throw Error(`incompatible currency (${am1.currency} vs${am2.currency})`); + } + + const x1 = BigInt(am1.value) * BigInt(amountFractionalBase) + BigInt(am1.fraction); + const x2 = BigInt(am2.value) * BigInt(amountFractionalBase) + BigInt(am2.fraction); + + const quotient = x1 / x2; + const remainderScaled = x1 % x2; + + return { + quotient: Number(quotient), + remainder: { + currency: am1.currency, + value: Number(remainderScaled / BigInt(amountFractionalBase)), + fraction: Number(remainderScaled % BigInt(amountFractionalBase)) + } + } + } + static sum(amounts: AmountLike[]): Result { if (amounts.length <= 0) { throw Error("can't sum zero amounts"); diff --git a/packages/taler-wallet-core/src/util/coinSelection.ts b/packages/taler-wallet-core/src/util/coinSelection.ts index 3b986d72b..af6dab2bb 100644 --- a/packages/taler-wallet-core/src/util/coinSelection.ts +++ b/packages/taler-wallet-core/src/util/coinSelection.ts @@ -689,18 +689,13 @@ export function selectWithdrawalDenominations( ); for (const d of denoms) { - let count = 0; const cost = Amounts.add( DenominationRecord.getValue(d), d.fees.feeWithdraw, ).amount; - for (;;) { - if (Amounts.cmp(remaining, cost) < 0) { - break; - } - remaining = Amounts.sub(remaining, cost).amount; - count++; - } + const res = Amounts.divmod(remaining, cost); + const count = res.quotient; + remaining = Amounts.sub(remaining, Amounts.mult(cost, count).amount).amount; if (count > 0) { totalCoinValue = Amounts.add( totalCoinValue,