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Merge pull request #36 from pacu/big-decimal
[#35] Use BigDecimal instead of Decimal
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,120 @@ | ||
| // | ||
| // Amount.swift | ||
| // | ||
| // | ||
| // Created by Pacu on 2024-01-01. | ||
| // | ||
|
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| import Foundation | ||
| import BigDecimal | ||
| /// An *non-negative* decimal ZEC amount represented as specified in ZIP-321. | ||
| /// Amount can be from 1 zatoshi (0.00000001) to the `maxSupply` of 21M ZEC (`21_000_000`) | ||
| public struct Amount: Equatable { | ||
| public enum AmountError: Error { | ||
| case negativeAmount | ||
| case greaterThanSupply | ||
| case tooManyFractionalDigits | ||
| case invalidTextInput | ||
| } | ||
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| static let maxFractionalDecimalDigits: Int = 8 | ||
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| static let zecRounding = Rounding(.toNearestOrEven, maxFractionalDecimalDigits) | ||
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| static let decimalHandler = NSDecimalNumberHandler( | ||
| roundingMode: NSDecimalNumber.RoundingMode.bankers, | ||
| scale: Int16(Self.maxFractionalDecimalDigits), | ||
| raiseOnExactness: true, | ||
| raiseOnOverflow: true, | ||
| raiseOnUnderflow: true, | ||
| raiseOnDivideByZero: true | ||
| ) | ||
|
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| static let maxSupply: BigDecimal = 21_000_000 | ||
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| static let zero = Amount(unchecked: 0) | ||
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| let value: BigDecimal | ||
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| /// Initializes an Amount from a `Decimal` number | ||
| /// - parameter value: decimal representation of the desired amount. **Important:** `Decimal` values with more than 8 fractional digits ** will be rounded** using bankers rounding. | ||
| /// - returns A valid ZEC amount | ||
| /// - throws `Amount.AmountError` then the provided value can't represent or can't be rounded to a non-negative ZEC decimal amount. | ||
| public init(value: Double) throws { | ||
| guard value >= 0 else { throw AmountError.negativeAmount } | ||
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| guard value <= Self.maxSupply.asDouble() else { throw AmountError.greaterThanSupply } | ||
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| try self.init(decimal: BigDecimal(value).round(Self.zecRounding)) | ||
| } | ||
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| /// Initializes an Amount from a `BigDecimal` number | ||
| /// - parameter decimal: decimal representation of the desired amount. **Important:** `Decimal` values with more than 8 fractional digits ** will be rounded** using bankers rounding. | ||
| /// - returns A valid ZEC amount | ||
| /// - throws `Amount.AmountError` then the provided value can't represent or can't be rounded to a non-negative ZEC decimal amount. | ||
| public init(decimal: BigDecimal) throws { | ||
| guard decimal >= 0 else { throw AmountError.negativeAmount } | ||
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| guard decimal <= Self.maxSupply else { throw AmountError.greaterThanSupply } | ||
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| guard decimal.significantFractionalDecimalDigits <= Self.maxFractionalDecimalDigits else { | ||
| throw AmountError.tooManyFractionalDigits | ||
| } | ||
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| guard decimal <= Self.maxSupply else { throw AmountError.greaterThanSupply } | ||
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| self.value = decimal | ||
| } | ||
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| /// Initializes an Amount from a `BigDecimal` number | ||
| /// - parameter decimal: decimal representation of the desired amount. **Important:** `Decimal` values with more than 8 fractional digits ** will be rounded** using bankers rounding. | ||
| /// - returns A valid ZEC amount | ||
| /// - throws `Amount.AmountError` then the provided value can't represent or can't be rounded to a non-negative ZEC decimal amount. | ||
| public init(decimal: Decimal) throws { | ||
| guard decimal >= 0 else { throw AmountError.negativeAmount } | ||
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| guard decimal.significantFractionalDecimalDigits <= Self.maxFractionalDecimalDigits else { | ||
| throw AmountError.tooManyFractionalDigits | ||
| } | ||
|
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| guard decimal <= Self.maxSupply.asDecimal() else { throw AmountError.greaterThanSupply } | ||
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| self.value = BigDecimal(decimal).round(Self.zecRounding) | ||
| } | ||
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| public init(string: String) throws { | ||
| let decimalAmount = BigDecimal(string).trim | ||
|
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| guard !decimalAmount.isNaN else { | ||
| throw AmountError.invalidTextInput | ||
| } | ||
|
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| guard decimalAmount.significantFractionalDecimalDigits <= Self.maxFractionalDecimalDigits else { | ||
| throw AmountError.tooManyFractionalDigits | ||
| } | ||
|
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| try self.init(decimal: decimalAmount) | ||
| } | ||
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| init(unchecked: BigDecimal) { | ||
| self.value = unchecked | ||
| } | ||
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| public func toString() -> String { | ||
| let decimal = value.round(Rounding(.toNearestOrEven, Self.maxFractionalDecimalDigits)).trim | ||
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| return decimal.asString(.plain) // this value is already validated. | ||
| } | ||
| } | ||
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| extension BigDecimal { | ||
| var significantFractionalDecimalDigits: Int { | ||
| return max(-exponent, 0) | ||
| } | ||
| } | ||
|
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| extension Decimal { | ||
| var significantFractionalDecimalDigits: Int { | ||
| return max(-exponent, 0) | ||
| } | ||
| } |
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