a16aecfa96
Why: big.Float is not an ideal type for dealing with monetary amounts, because no matter how high the precision, some non-integer decimal values can not be represented exactly in base-2 floating point. Also, storing gob-encoded big.Float values in the database makes it very hard to use those values in meaningful queries, making it difficult to do any sort of analysis on billing. For better accuracy, then, we can just represent monetary values as integers (in whatever base units are appropriate for the currency). For example, STORJ tokens or Bitcoins can not be split into pieces smaller than 10^-8, so we can store amounts of STORJ or BTC with precision simply by moving the decimal point 8 digits to the right. For USD values (assuming we don't want to deal with fractional cents), we can move the decimal point 2 digits to the right. To make it easier and less error-prone to deal with the math involved, I introduce here a new type, monetary.Amount, instances of which have an associated value _and_ a currency. Change-Id: I03395d52f0e2473cf301361f6033722b54640265
78 lines
2.1 KiB
Go
78 lines
2.1 KiB
Go
// Copyright (C) 2019 Storj Labs, Inc.
|
|
// See LICENSE for copying information.
|
|
|
|
package stripecoinpayments
|
|
|
|
import (
|
|
"context"
|
|
"time"
|
|
|
|
"github.com/shopspring/decimal"
|
|
"github.com/zeebo/errs"
|
|
"go.uber.org/zap"
|
|
|
|
"storj.io/common/sync2"
|
|
"storj.io/storj/satellite/payments/monetary"
|
|
)
|
|
|
|
// convertToCents convert amount to USD cents with given rate.
|
|
func convertToCents(rate decimal.Decimal, amount monetary.Amount) int64 {
|
|
amountDecimal := amount.AsDecimal()
|
|
usd := amountDecimal.Mul(rate)
|
|
usdCents := usd.Shift(2)
|
|
return usdCents.Round(0).IntPart()
|
|
}
|
|
|
|
// convertFromCents convert amount in cents to a StorjTokenAmount with given rate.
|
|
func convertFromCents(rate decimal.Decimal, usdCents int64) monetary.Amount {
|
|
usd := decimal.NewFromInt(usdCents).Shift(-2)
|
|
numStorj := usd.Div(rate)
|
|
return monetary.AmountFromDecimal(numStorj, monetary.USDollars)
|
|
}
|
|
|
|
// ErrConversion defines version service error.
|
|
var ErrConversion = errs.Class("conversion service")
|
|
|
|
// ConversionService updates conversion rates in a loop.
|
|
//
|
|
// architecture: Service
|
|
type ConversionService struct {
|
|
log *zap.Logger
|
|
service *Service
|
|
Cycle sync2.Cycle
|
|
}
|
|
|
|
// NewConversionService creates new instance of ConversionService.
|
|
func NewConversionService(log *zap.Logger, service *Service, interval time.Duration) *ConversionService {
|
|
return &ConversionService{
|
|
log: log,
|
|
service: service,
|
|
Cycle: *sync2.NewCycle(interval),
|
|
}
|
|
}
|
|
|
|
// Run runs loop which updates conversion rates for service.
|
|
func (conversion *ConversionService) Run(ctx context.Context) (err error) {
|
|
defer mon.Task()(&ctx)(&err)
|
|
|
|
return ErrConversion.Wrap(conversion.Cycle.Run(ctx,
|
|
func(ctx context.Context) error {
|
|
conversion.log.Debug("running conversion rates update cycle")
|
|
|
|
if err := conversion.service.UpdateRates(ctx); err != nil {
|
|
conversion.log.Error("conversion rates update cycle failed", zap.Error(ErrChore.Wrap(err)))
|
|
}
|
|
|
|
return nil
|
|
},
|
|
))
|
|
}
|
|
|
|
// Close closes underlying cycle.
|
|
func (conversion *ConversionService) Close() (err error) {
|
|
defer mon.Task()(nil)(&err)
|
|
|
|
conversion.Cycle.Close()
|
|
return nil
|
|
}
|