feat: add mpre endpoints

src/application/services/payment_quote_service.py

@@ -0,0 +1,53 @@
+from __future__ import annotations
+from dataclasses import dataclass
+from datetime import datetime,timezone
+from decimal import Decimal,ROUND_UP
+from src.application.contracts import ICache,ILogger
+from src.application.domain.exceptions import ServiceUnavailableException
+from src.infrastructure.config import settings
+
+
+@dataclass(slots=True)
+class PaymentQuote:
+    usdt_amount: Decimal
+    usdt_exchange_rate: Decimal
+    gas_fee: Decimal
+    service_fee: Decimal
+    total_price: Decimal
+    service_fee_rate: Decimal
+    created_at: datetime
+
+
+class PaymentQuoteService:
+    def __init__(self, *, remote_cache: ICache, logger: ILogger):
+        self._remote_cache = remote_cache
+        self._logger = logger
+
+
+    async def get_quote(self, usdt_amount: Decimal) -> PaymentQuote:
+        rate_raw = await self._remote_cache.hget('tradex:rub:rate','value')
+        gas_raw = await self._remote_cache.hget('gwei:eth:last','normal_rub')
+        self._logger.info(f'Actual market values: rate={rate_raw}, gas={gas_raw}')
+
+        if rate_raw is None:
+            self._logger.error('Exchange rate unavailable')
+            raise ServiceUnavailableException(message='Exchange rate unavailable')
+
+        if gas_raw is None:
+            self._logger.error('Exchange gas unavailable')
+            raise ServiceUnavailableException(message='Exchange gas unavailable')
+
+        gas_fee = Decimal(gas_raw).quantize(Decimal('0.00'), rounding=ROUND_UP)
+        usdt_exchange_rate = Decimal(rate_raw).quantize(Decimal('0.00'), rounding=ROUND_UP)
+        service_fee = (usdt_amount * usdt_exchange_rate * settings.PAYMENT_SERVICE_FEE_RATE).quantize(Decimal('0.01'))
+        total_price = (usdt_amount * usdt_exchange_rate + service_fee + gas_fee).quantize(Decimal('0.01'))
+
+        return PaymentQuote(
+            usdt_amount=usdt_amount,
+            usdt_exchange_rate=usdt_exchange_rate,
+            gas_fee=gas_fee,
+            service_fee=service_fee,
+            total_price=total_price,
+            service_fee_rate=settings.PAYMENT_SERVICE_FEE_RATE,
+            created_at=datetime.now(timezone.utc),
+        )