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,
        )