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/*
* This file is part of GNU Taler
* (C) 2021 Taler Systems S.A.
*
* GNU Taler is free software; you can redistribute it and/or modify it under the
* terms of the GNU General Public License as published by the Free Software
* Foundation; either version 3, or (at your option) any later version.
*
* GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
* A PARTICULAR PURPOSE. See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along with
* GNU Taler; see the file COPYING. If not, see <http://www.gnu.org/licenses/>
*/
import Foundation
enum AmountError: Error {
case invalidStringRepresentation
case incompatibleCurrency
case invalidAmount
case negativeAmount
}
class Amount: Codable, CustomStringConvertible {
private static let maxValue: UInt64 = 1 << 52
private static let fractionalBase: UInt32 = 100000000
private static let fractionalBaseDigits: UInt = 8
var currency: String
var value: UInt64
var fraction: UInt32
var description: String {
if fraction == 0 {
return "\(currency):\(value)"
} else {
var frac = fraction
var fracStr = ""
while (frac > 0) {
fracStr += "\(frac / (Amount.fractionalBase / 10))"
frac = (frac * 10) % Amount.fractionalBase
}
return "\(currency):\(value).\(fracStr)"
}
}
var valid: Bool {
return (value <= Amount.maxValue && currency != "")
}
init(fromString string: String) throws {
guard let separatorIndex = string.firstIndex(of: ":") else { throw AmountError.invalidStringRepresentation }
self.currency = String(string[..<separatorIndex])
let amountStr = String(string[string.index(separatorIndex, offsetBy: 1)...])
if let dotIndex = amountStr.firstIndex(of: ".") {
let valueStr = String(amountStr[..<dotIndex])
let fractionStr = String(amountStr[string.index(dotIndex, offsetBy: 1)...])
guard let _value = UInt64(valueStr) else { throw AmountError.invalidStringRepresentation }
self.value = _value
self.fraction = 0
var digitValue = Amount.fractionalBase / 10
for char in fractionStr {
guard let digit = char.wholeNumberValue else { throw AmountError.invalidStringRepresentation }
self.fraction += digitValue * UInt32(digit)
digitValue /= 10
}
} else {
guard let _value = UInt64(amountStr) else { throw AmountError.invalidStringRepresentation }
self.value = _value
self.fraction = 0
}
guard self.valid else { throw AmountError.invalidAmount }
}
init(currency: String, value: UInt64, fraction: UInt32) {
self.currency = currency
self.value = value
self.fraction = fraction
}
init(fromDecoder decoder: Decoder) throws {
let container = try decoder.singleValueContainer()
let string = try container.decode(String.self)
/* TODO: de-duplicate */
guard let separatorIndex = string.firstIndex(of: ":") else { throw AmountError.invalidStringRepresentation }
self.currency = String(string[..<separatorIndex])
let amountStr = String(string[string.index(separatorIndex, offsetBy: 1)...])
if let dotIndex = amountStr.firstIndex(of: ".") {
let valueStr = String(amountStr[..<dotIndex])
let fractionStr = String(amountStr[string.index(dotIndex, offsetBy: 1)...])
guard let _value = UInt64(valueStr) else { throw AmountError.invalidStringRepresentation }
self.value = _value
self.fraction = 0
var digitValue = Amount.fractionalBase / 10
for char in fractionStr {
guard let digit = char.wholeNumberValue else { throw AmountError.invalidStringRepresentation }
self.fraction += digitValue * UInt32(digit)
digitValue /= 10
}
} else {
guard let _value = UInt64(amountStr) else { throw AmountError.invalidStringRepresentation }
self.value = _value
self.fraction = 0
}
guard self.valid else { throw AmountError.invalidAmount }
}
func copy() -> Amount {
return Amount(currency: self.currency, value: self.value, fraction: self.fraction)
}
func normalizedCopy() throws -> Amount {
let amount = self.copy()
try amount.normalize()
return amount
}
func encode(to encoder: Encoder) throws {
var container = encoder.singleValueContainer()
try container.encode(self.description)
}
func normalize() throws {
if !valid {
throw AmountError.invalidAmount
}
self.value += UInt64(self.fraction / Amount.fractionalBase)
self.fraction = self.fraction % Amount.fractionalBase
if !valid {
throw AmountError.invalidAmount
}
}
static func + (left: Amount, right: Amount) throws -> Amount {
if left.currency != right.currency {
throw AmountError.incompatibleCurrency
}
let leftNormalized = try left.normalizedCopy()
let rightNormalized = try right.normalizedCopy()
let result: Amount = leftNormalized
result.value += rightNormalized.value
result.fraction += rightNormalized.fraction
try result.normalize()
return result
}
static func - (left: Amount, right: Amount) throws -> Amount {
if left.currency != right.currency {
throw AmountError.incompatibleCurrency
}
let leftNormalized = try left.normalizedCopy()
let rightNormalized = try right.normalizedCopy()
if (leftNormalized.fraction < rightNormalized.fraction) {
guard leftNormalized.value != 0 else { throw AmountError.negativeAmount }
leftNormalized.value -= 1
leftNormalized.fraction += Amount.fractionalBase
}
guard leftNormalized.value >= rightNormalized.value else { throw AmountError.negativeAmount }
let diff = Amount.zero(currency: left.currency)
diff.value = leftNormalized.value - rightNormalized.value
diff.fraction = leftNormalized.fraction - rightNormalized.fraction
try diff.normalize()
return diff
}
static func == (left: Amount, right: Amount) throws -> Bool {
if left.currency != right.currency {
throw AmountError.incompatibleCurrency
}
let leftNormalized = try left.normalizedCopy()
let rightNormalized = try right.normalizedCopy()
return (leftNormalized.value == rightNormalized.value && leftNormalized.fraction == rightNormalized.fraction)
}
static func < (left: Amount, right: Amount) throws -> Bool {
if left.currency != right.currency {
throw AmountError.incompatibleCurrency
}
let leftNormalized = try left.normalizedCopy()
let rightNormalized = try right.normalizedCopy()
if (leftNormalized.value == rightNormalized.value) {
return (leftNormalized.fraction < rightNormalized.fraction)
} else {
return (leftNormalized.value < rightNormalized.value)
}
}
static func > (left: Amount, right: Amount) throws -> Bool {
return try right < left
}
static func zero(currency: String) -> Amount {
return Amount(currency: currency, value: 0, fraction: 0)
}
}
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