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Diffstat (limited to 'taler-kotlin-android/src/main/java/net/taler/common/Amount.kt')
| -rw-r--r-- | taler-kotlin-android/src/main/java/net/taler/common/Amount.kt | 281 |
1 files changed, 281 insertions, 0 deletions
diff --git a/taler-kotlin-android/src/main/java/net/taler/common/Amount.kt b/taler-kotlin-android/src/main/java/net/taler/common/Amount.kt new file mode 100644 index 0000000..3e3bd0a --- /dev/null +++ b/taler-kotlin-android/src/main/java/net/taler/common/Amount.kt @@ -0,0 +1,281 @@ +/* + * This file is part of GNU Taler + * (C) 2020 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/> + */ + +package net.taler.common + +import android.os.Build +import kotlinx.serialization.KSerializer +import kotlinx.serialization.Serializable +import kotlinx.serialization.Serializer +import kotlinx.serialization.encoding.Decoder +import kotlinx.serialization.encoding.Encoder +import java.text.DecimalFormat +import java.text.DecimalFormatSymbols +import java.text.NumberFormat +import kotlin.math.floor +import kotlin.math.pow +import kotlin.math.roundToInt + +public class AmountParserException(msg: String? = null, cause: Throwable? = null) : + Exception(msg, cause) + +public class AmountOverflowException(msg: String? = null, cause: Throwable? = null) : + Exception(msg, cause) + +@Serializable(with = KotlinXAmountSerializer::class) +public data class Amount( + /** + * name of the currency using either a three-character ISO 4217 currency code, + * or a regional currency identifier starting with a "*" followed by at most 10 characters. + * ISO 4217 exponents in the name are not supported, + * although the "fraction" is corresponds to an ISO 4217 exponent of 6. + */ + val currency: String, + + /** + * The integer part may be at most 2^52. + * Note that "1" here would correspond to 1 EUR or 1 USD, depending on currency, not 1 cent. + */ + val value: Long, + + /** + * Unsigned 32 bit fractional value to be added to value representing + * an additional currency fraction, in units of one hundred millionth (1e-8) + * of the base currency value. For example, a fraction + * of 50_000_000 would correspond to 50 cents. + */ + val fraction: Int, + + /** + * Currency specification for amount + */ + val spec: CurrencySpecification? = null, +) : Comparable<Amount> { + + public companion object { + + private const val FRACTIONAL_BASE: Int = 100000000 // 1e8 + + private val REGEX_CURRENCY = Regex("""^[-_*A-Za-z0-9]{1,12}$""") + public val MAX_VALUE: Long = 2.0.pow(52).toLong() + private const val MAX_FRACTION_LENGTH = 8 + public const val MAX_FRACTION: Int = 99_999_999 + + public fun zero(currency: String): Amount { + return Amount(checkCurrency(currency), 0, 0) + } + + public fun fromJSONString(str: String): Amount { + val split = str.split(":") + if (split.size != 2) throw AmountParserException("Invalid Amount Format") + return fromString(split[0], split[1]) + } + + public fun fromString(currency: String, str: String): Amount { + // value + val valueSplit = str.split(".") + val value = checkValue(valueSplit[0].toLongOrNull()) + // fraction + val fraction: Int = if (valueSplit.size > 1) { + val fractionStr = valueSplit[1] + if (fractionStr.length > MAX_FRACTION_LENGTH) + throw AmountParserException("Fraction $fractionStr too long") + checkFraction(fractionStr.getFraction()) + } else 0 + return Amount(checkCurrency(currency), value, fraction) + } + + public fun isValidAmountStr(str: String): Boolean { + if (str.count { it == '.' } > 1) return false + val split = str.split(".") + try { + checkValue(split[0].toLongOrNull()) + } catch (e: AmountParserException) { + return false + } + // also check fraction, if it exists + if (split.size > 1) { + val fractionStr = split[1] + if (fractionStr.length > MAX_FRACTION_LENGTH) return false + val fraction = fractionStr.getFraction() ?: return false + return fraction <= MAX_FRACTION + } + return true + } + + private fun String.getFraction(): Int? { + return "0.$this".toDoubleOrNull() + ?.times(FRACTIONAL_BASE) + ?.roundToInt() + } + + public fun min(currency: String): Amount = Amount(currency, 0, 1) + public fun max(currency: String): Amount = Amount(currency, MAX_VALUE, MAX_FRACTION) + + + internal fun checkCurrency(currency: String): String { + if (!REGEX_CURRENCY.matches(currency)) + throw AmountParserException("Invalid currency: $currency") + return currency + } + + internal fun checkValue(value: Long?): Long { + if (value == null || value > MAX_VALUE) + throw AmountParserException("Value $value greater than $MAX_VALUE") + return value + } + + internal fun checkFraction(fraction: Int?): Int { + if (fraction == null || fraction > MAX_FRACTION) + throw AmountParserException("Fraction $fraction greater than $MAX_FRACTION") + return fraction + } + + } + + public val amountStr: String + get() = if (fraction == 0) "$value" else { + var f = fraction + var fractionStr = "" + while (f > 0) { + fractionStr += f / (FRACTIONAL_BASE / 10) + f = (f * 10) % FRACTIONAL_BASE + } + "$value.$fractionStr" + } + + public operator fun plus(other: Amount): Amount { + check(currency == other.currency) { "Can only subtract from same currency" } + val resultValue = + value + other.value + floor((fraction + other.fraction).toDouble() / FRACTIONAL_BASE).toLong() + if (resultValue > MAX_VALUE) + throw AmountOverflowException() + val resultFraction = (fraction + other.fraction) % FRACTIONAL_BASE + return Amount(currency, resultValue, resultFraction) + } + + public operator fun times(factor: Int): Amount { + // TODO consider replacing with a faster implementation + if (factor == 0) return zero(currency) + var result = this + for (i in 1 until factor) result += this + return result + } + + public fun withCurrency(currency: String): Amount { + return Amount(checkCurrency(currency), this.value, this.fraction) + } + + fun withSpec(spec: CurrencySpecification?) = copy(spec = spec) + + public operator fun minus(other: Amount): Amount { + check(currency == other.currency) { "Can only subtract from same currency" } + var resultValue = value + var resultFraction = fraction + if (resultFraction < other.fraction) { + if (resultValue < 1L) + throw AmountOverflowException() + resultValue-- + resultFraction += FRACTIONAL_BASE + } + check(resultFraction >= other.fraction) + resultFraction -= other.fraction + if (resultValue < other.value) + throw AmountOverflowException() + resultValue -= other.value + return Amount(currency, resultValue, resultFraction) + } + + public fun isZero(): Boolean { + return value == 0L && fraction == 0 + } + + public fun toJSONString(): String { + return "$currency:$amountStr" + } + + override fun toString() = toString( + showSymbol = true, + negative = false, + ) + + fun toString( + showSymbol: Boolean = true, + negative: Boolean = false, + symbols: DecimalFormatSymbols = DecimalFormat().decimalFormatSymbols, + ): String { + // We clone the object to safely/cleanly modify it + val s = symbols.clone() as DecimalFormatSymbols + val amount = (if (negative) "-$amountStr" else amountStr).toBigDecimal() + + // No currency spec, so we render normally + if (spec == null) { + val format = NumberFormat.getInstance() + format.maximumFractionDigits = MAX_FRACTION_LENGTH + format.minimumFractionDigits = 0 + if (Build.VERSION.SDK_INT >= 34) { + s.groupingSeparator = s.monetaryGroupingSeparator + } + s.decimalSeparator = s.monetaryDecimalSeparator + (format as DecimalFormat).decimalFormatSymbols = s + + val fmt = format.format(amount) + return if (showSymbol) "$fmt $currency" else fmt + } + + // There is currency spec, so we can do things right + val format = NumberFormat.getCurrencyInstance() + format.maximumFractionDigits = spec.numFractionalNormalDigits + format.minimumFractionDigits = spec.numFractionalTrailingZeroDigits + s.currencySymbol = spec.symbol ?: "" + (format as DecimalFormat).decimalFormatSymbols = s + + val fmt = format.format(amount) + return if (showSymbol) { + // If no symbol, then we use the currency string + if (spec.symbol != null) fmt else "$fmt $currency" + } else { + // We should do better than manually removing the symbol here + fmt.replace(s.currencySymbol, "").trim() + } + } + + override fun compareTo(other: Amount): Int { + check(currency == other.currency) { "Can only compare amounts with the same currency" } + when { + value == other.value -> { + if (fraction < other.fraction) return -1 + if (fraction > other.fraction) return 1 + return 0 + } + value < other.value -> return -1 + else -> return 1 + } + } + +} + +@Suppress("EXPERIMENTAL_API_USAGE") +@Serializer(forClass = Amount::class) +internal object KotlinXAmountSerializer : KSerializer<Amount> { + override fun serialize(encoder: Encoder, value: Amount) { + encoder.encodeString(value.toJSONString()) + } + + override fun deserialize(decoder: Decoder): Amount { + return Amount.fromJSONString(decoder.decodeString()) + } +} |