feat: add withdraw

src/application/services/sbp_withdrawal_quote_service.py

@@ -0,0 +1,64 @@
+from __future__ import annotations
+from dataclasses import dataclass
+from decimal import Decimal,ROUND_DOWN,ROUND_UP
+from src.application.contracts import ICache,ILogger
+from src.application.domain.exceptions import OrderTotalOutOfRangeException,ServiceUnavailableException
+
+MIN_SBP_WITHDRAWAL_USDT: Decimal=Decimal('100')
+MAX_SBP_WITHDRAWAL_USDT: Decimal=Decimal('5000')
+
+_FEE_TIERS: tuple[tuple[Decimal,Decimal,Decimal],...]=(
+    (Decimal('100'),Decimal('2000'),Decimal('0.08')),
+    (Decimal('2000.01'),Decimal('4000'),Decimal('0.06')),
+    (Decimal('4000.01'),Decimal('5000'),Decimal('0.04')),
+)
+
+
+@dataclass(slots=True)
+class SbpWithdrawalQuote:
+    usdt_amount: Decimal
+    rub_amount: Decimal
+    usdt_exchange_rate: Decimal
+    service_fee_rate: Decimal
+    service_fee_usdt: Decimal
+
+
+class SbpWithdrawalQuoteService:
+    def __init__(self,*,remote_cache: ICache,logger: ILogger):
+        self._remote_cache=remote_cache
+        self._logger=logger
+
+
+    async def _load_rate(self) -> Decimal:
+        rate_raw=await self._remote_cache.hget('tradex:rub:rate','value')
+        self._logger.info(f'Actual market value for SBP withdrawal: rate={rate_raw}')
+        if rate_raw is None:
+            raise ServiceUnavailableException(message='Exchange rate unavailable')
+        return Decimal(rate_raw).quantize(Decimal('0.00'),rounding=ROUND_UP)
+
+
+    @staticmethod
+    def _fee_rate(usdt_amount: Decimal) -> Decimal:
+        for lo,hi,rate in _FEE_TIERS:
+            if lo<=usdt_amount<=hi:
+                return rate
+        raise OrderTotalOutOfRangeException(message='Withdrawal amount is out of range')
+
+
+    async def get_quote(self,usdt_amount: Decimal) -> SbpWithdrawalQuote:
+        if usdt_amount<MIN_SBP_WITHDRAWAL_USDT:
+            raise OrderTotalOutOfRangeException(message='Withdrawal amount is below minimum allowed amount')
+        if usdt_amount>MAX_SBP_WITHDRAWAL_USDT:
+            raise OrderTotalOutOfRangeException(message='Withdrawal amount exceeds maximum allowed amount')
+        rate=await self._load_rate()
+        fee_rate=self._fee_rate(usdt_amount)
+        service_fee=(usdt_amount*fee_rate).quantize(Decimal('0.01'))
+        payout_usdt=(usdt_amount-service_fee).quantize(Decimal('0.01'))
+        rub_amount=(payout_usdt*rate).quantize(Decimal('1'),rounding=ROUND_DOWN)
+        return SbpWithdrawalQuote(
+            usdt_amount=usdt_amount,
+            rub_amount=rub_amount,
+            usdt_exchange_rate=rate,
+            service_fee_rate=fee_rate,
+            service_fee_usdt=service_fee,
+        )