51 lines
1.6 KiB
Go
51 lines
1.6 KiB
Go
package moneybase
|
|
|
|
import (
|
|
"math/big"
|
|
"strings"
|
|
|
|
decimalbase "git.sendico.io/tech/sxchnge/bff/pkg/decimal"
|
|
"git.sendico.io/tech/sxchnge/bff/pkg/merrors"
|
|
)
|
|
|
|
// SourceRoundedConversionMatches reports whether sourceAmount is the minimum
|
|
// source-scale amount that covers targetAmount at rate.
|
|
func SourceRoundedConversionMatches(sourceAmount, targetAmount, rate string, sourceScale uint32) (bool, error) {
|
|
if err := ValidateScale("source scale", sourceScale); err != nil {
|
|
return false, err
|
|
}
|
|
source, err := positiveRat(sourceAmount, "source amount")
|
|
if err != nil {
|
|
return false, err
|
|
}
|
|
target, err := positiveRat(targetAmount, "target amount")
|
|
if err != nil {
|
|
return false, err
|
|
}
|
|
rateRat, err := positiveRat(rate, "conversion rate")
|
|
if err != nil {
|
|
return false, err
|
|
}
|
|
exactSource := new(big.Rat).Quo(target, rateRat)
|
|
roundedSource := ceilDecimalToScale(exactSource, sourceScale)
|
|
return roundedSource.Cmp(source) == 0 && source.Cmp(exactSource) >= 0, nil
|
|
}
|
|
|
|
func positiveRat(value string, field string) (*big.Rat, error) {
|
|
parsed, err := decimalbase.RatFromString(strings.TrimSpace(value))
|
|
if err != nil || parsed.Sign() <= 0 {
|
|
return nil, merrors.InvalidArgument(field + " must be a positive decimal")
|
|
}
|
|
return parsed, nil
|
|
}
|
|
|
|
func ceilDecimalToScale(value *big.Rat, scale uint32) *big.Rat {
|
|
factor := new(big.Int).Exp(big.NewInt(10), big.NewInt(int64(scale)), nil)
|
|
scaled := new(big.Rat).Mul(value, new(big.Rat).SetInt(factor))
|
|
q, r := new(big.Int).QuoRem(scaled.Num(), scaled.Denom(), new(big.Int))
|
|
if r.Sign() > 0 {
|
|
q.Add(q, big.NewInt(1))
|
|
}
|
|
return new(big.Rat).SetFrac(q, factor)
|
|
}
|