feat(channel-donation-calculate): 채널 후원 정산 조회 기능을 추가한다

src/main/kotlin/kr/co/vividnext/sodalive/calculate/channelDonation/ChannelDonationSettlementCalculator.kt

@@ -0,0 +1,50 @@
+package kr.co.vividnext.sodalive.calculate.channelDonation
+
+import java.math.BigDecimal
+import java.math.RoundingMode
+
+data class ChannelDonationSettlementAmount(
+    val krw: Int,
+    val fee: Int,
+    val settlementAmount: Int,
+    val withholdingTax: Int,
+    val depositAmount: Int
+)
+
+object ChannelDonationSettlementCalculator {
+    private val KRW_PER_CAN = BigDecimal("100")
+    private val FEE_RATE = BigDecimal("0.066")
+    private val SETTLEMENT_RATE = BigDecimal("0.85")
+    private val WITHHOLDING_TAX_RATE = BigDecimal("0.033")
+
+    fun calculate(totalCan: Int): ChannelDonationSettlementAmount {
+        // 원화 = 캔 * 100
+        val krw = BigDecimal(totalCan).multiply(KRW_PER_CAN).setScale(0, RoundingMode.HALF_UP).toInt()
+
+        // 수수료 = 원화 * 6.6%
+        val fee = BigDecimal(krw).multiply(FEE_RATE).setScale(0, RoundingMode.HALF_UP).toInt()
+
+        // 정산금액 = (원화 - 수수료) * 85%
+        val settlementAmount = BigDecimal(krw - fee)
+            .multiply(SETTLEMENT_RATE)
+            .setScale(0, RoundingMode.HALF_UP)
+            .toInt()
+
+        // 원천세 = 정산금액 * 3.3%
+        val withholdingTax = BigDecimal(settlementAmount)
+            .multiply(WITHHOLDING_TAX_RATE)
+            .setScale(0, RoundingMode.HALF_UP)
+            .toInt()
+
+        // 입금액 = 정산금액 - 원천세
+        val depositAmount = settlementAmount - withholdingTax
+
+        return ChannelDonationSettlementAmount(
+            krw = krw,
+            fee = fee,
+            settlementAmount = settlementAmount,
+            withholdingTax = withholdingTax,
+            depositAmount = depositAmount
+        )
+    }
+}