money.go

// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package money

import (
	"errors"

	pb "github.com/GoogleCloudPlatform/microservices-demo/src/checkoutservice/genproto"
)

const (
	nanosMin = -999999999
	nanosMax = +999999999
	nanosMod = 1000000000
)

var (
	ErrInvalidValue        = errors.New("one of the specified money values is invalid")
	ErrMismatchingCurrency = errors.New("mismatching currency codes")
)

// IsValid checks if specified value has a valid units/nanos signs and ranges.
func IsValid(m pb.Money) bool {
	return signMatches(m) && validNanos(m.GetNanos())
}

func signMatches(m pb.Money) bool {
	return m.GetNanos() == 0 || m.GetUnits() == 0 || (m.GetNanos() < 0) == (m.GetUnits() < 0)
}

func validNanos(nanos int32) bool { return nanosMin <= nanos && nanos <= nanosMax }

// IsZero returns true if the specified money value is equal to zero.
func IsZero(m pb.Money) bool { return m.GetUnits() == 0 && m.GetNanos() == 0 }

// IsPositive returns true if the specified money value is valid and is
// positive.
func IsPositive(m pb.Money) bool {
	return IsValid(m) && m.GetUnits() > 0 || (m.GetUnits() == 0 && m.GetNanos() > 0)
}

// IsNegative returns true if the specified money value is valid and is
// negative.
func IsNegative(m pb.Money) bool {
	return IsValid(m) && m.GetUnits() < 0 || (m.GetUnits() == 0 && m.GetNanos() < 0)
}

// AreSameCurrency returns true if values l and r have a currency code and
// they are the same values.
func AreSameCurrency(l, r pb.Money) bool {
	return l.GetCurrencyCode() == r.GetCurrencyCode() && l.GetCurrencyCode() != ""
}

// AreEquals returns true if values l and r are the equal, including the
// currency. This does not check validity of the provided values.
func AreEquals(l, r pb.Money) bool {
	return l.GetCurrencyCode() == r.GetCurrencyCode() &&
		l.GetUnits() == r.GetUnits() && l.GetNanos() == r.GetNanos()