fees.go

package util

import (
	"net/http"

	"github.com/OpenBazaar/wallet-interface"
)

type httpClient interface {
	Get(string) (*http.Response, error)
}

// Fees describe
type Fees struct {
	FastestFee  uint64
	HalfHourFee uint64
	HourFee     uint64
}

type FeeProvider struct {
	maxFee           uint64
	priorityFee      uint64
	normalFee        uint64
	economicFee      uint64
	superEconomicFee uint64

	exchangeRates wallet.ExchangeRates
}

// We will target a fee per byte such that it would equal
// 0.1 USD cent for economic, 1 USD cents for normal and
// 5 USD cents for priority for a median (226 byte) transaction.
type FeeTargetInUSDCents float64

const (
	EconomicTarget FeeTargetInUSDCents = 0.1
	NormalTarget   FeeTargetInUSDCents = 1
	PriorityTarget FeeTargetInUSDCents = 5

	AverageTransactionSize = 226
)

func NewFeeProvider(maxFee, priorityFee, normalFee, economicFee, superEconomicFee uint64, exchangeRates wallet.ExchangeRates) *FeeProvider {
	return &FeeProvider{
		maxFee:           maxFee,
		priorityFee:      priorityFee,
		normalFee:        normalFee,
		economicFee:      economicFee,
		superEconomicFee: superEconomicFee,
		exchangeRates:    exchangeRates,
	}
}

func (fp *FeeProvider) GetFeePerByte(feeLevel wallet.FeeLevel) uint64 {
	defaultFee := func() uint64 {
		switch feeLevel {
		case wallet.PRIOIRTY:
			return fp.priorityFee
		case wallet.NORMAL:
			return fp.normalFee
		case wallet.ECONOMIC:
			return fp.economicFee
		case wallet.FEE_BUMP:
			return fp.priorityFee * 2
		default:
			return fp.normalFee
		}
	}
	if fp.exchangeRates == nil {
		return defaultFee()
	}

	rate, err := fp.exchangeRates.GetLatestRate("USD")
	if err != nil || rate == 0 {
		return defaultFee()
	}

	var target FeeTargetInUSDCents
	switch feeLevel {
	case wallet.PRIOIRTY:
		target = PriorityTarget
	case wallet.NORMAL:
		target = NormalTarget
	case wallet.ECONOMIC:
		target = EconomicTarget
	case wallet.SUPER_ECONOMIC:
		return fp.superEconomicFee
	case wallet.FEE_BUMP:
		target = PriorityTarget * 2
	default:
		target = NormalTarget
	}

	feePerByte := (((float64(target) / 100) / rate) * 100000000) / AverageTransactionSize

	if uint64(feePerByte) > fp.maxFee {
		return fp.maxFee
	}

	if uint64(feePerByte) == 0 {
		return 1
	}

	return uint64(feePerByte)
}