"""赎回服务：校验持仓 → 减仓 + 余额入账（单事务原子）。"""
from __future__ import annotations

from decimal import ROUND_HALF_UP, Decimal

from sqlalchemy.ext.asyncio import AsyncSession

from model.sys_user import SysUser
from repositories.fin_account import FinAccountRepo
from repositories.fin_holdings import FinHoldingsRepo
from repositories.fin_product import FinProductRepo
from schemas.holdings import HoldingResp
from schemas.redeem import RedeemResp
from utils.exceptions import ForbiddenError, NotFoundError, ParamError

_MONEY = Decimal("0.01")
_SHARES = Decimal("0.0001")


async def redeem(
    db: AsyncSession, user: SysUser, product_id: int, shares: Decimal
) -> RedeemResp:
    """赎回基金：校验通过后减仓并按净值入账，全程单事务。

    - 仅客户可赎回；
    - 产品须存在且净值非空；
    - 持仓须存在且份额 > 0，赎回份额不得超过持仓份额；
    - 减仓（归 0 时置'已清仓'）+ 入账要么都成、要么都回滚。
    """
    if user.user_type != "CUSTOMER":
        raise ForbiddenError("仅客户账号可赎回")

    shares = shares.quantize(_SHARES, rounding=ROUND_HALF_UP)
    if shares <= 0:
        raise ParamError("赎回份额须大于 0")

    product = await FinProductRepo(db).get(product_id)
    if product is None:
        raise NotFoundError("产品不存在")
    if product.nav is None:
        raise ParamError("产品暂无净值，无法赎回")

    account_repo = FinAccountRepo(db)
    holdings_repo = FinHoldingsRepo(db)

    holding = await holdings_repo.get_by_customer_product(user.id, product_id)
    if holding is None or holding.shares <= 0:
        raise ParamError("无可赎回份额")
    if holding.shares < shares:
        raise ParamError("可赎回份额不足")

    credited = (shares * product.nav).quantize(_MONEY, rounding=ROUND_HALF_UP)
    if credited <= 0:
        raise ParamError("赎回金额过低")

    try:
        if not await holdings_repo.redeem(user.id, product_id, shares):
            raise ParamError("可赎回份额不足")
        await account_repo.credit_balance(user.id, credited)
        await db.commit()
    except Exception:
        await db.rollback()
        raise

    account = await account_repo.get_by_customer_id(user.id)
    holding = await holdings_repo.get_by_customer_product(user.id, product_id)
    return RedeemResp(
        balance=account.balance,
        holding=HoldingResp(
            id=holding.id,
            customer_id=holding.customer_id,
            product_id=holding.product_id,
            shares=holding.shares,
            cost_amount=holding.cost_amount,
            current_value=holding.current_value,
            profit_loss=holding.profit_loss,
            profit_ratio=holding.profit_ratio,
            status=holding.status,
        ),
    )