RefundAvailability.kt

/*
 * This file is part of GNU Taler
 * (C) 2026 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.merchantpos.refund

import net.taler.common.Amount
import net.taler.common.ExternalPayment
import net.taler.merchantlib.OrderHistoryEntry
import net.taler.merchantpos.checkout.Checkout

internal fun OrderHistoryEntry.talerRefundRemaining(): Amount
{
    val zero = Amount.zero(amount.currency)
    if (!paid ||
        !refundable ||
        hasPendingRefund)
    {
        return zero
    }
    val refunded = refundAmount ?: if (refunded) amount else zero
    return if (refunded >= amount) zero else amount - refunded
}

/** Count a locally recorded refund only once when it also appears on the backend. */
internal fun OrderHistoryEntry.externalRefundRemaining(
    payment: ExternalPayment,
    checkout: Checkout?,
): Amount
{
    val zero = Amount.zero(payment.amount.currency)
    val refunds =
        refundsExternal
            .filter {
                it.paymentId == payment.id ||
                    (it.paymentId == null && it.method == payment.method)
            }.associate { it.id to it.amount }
            .toMutableMap()
    checkout?.refunds?.filter { it.paymentId == payment.id }?.forEach {
        refunds[it.id] = maxOf(refunds[it.id] ?: zero, it.amount)
    }
    val returned = refunds.values.fold(zero) { sum, value -> sum + value }
    return if (returned >= payment.amount) zero else payment.amount - returned
}