"""申购服务：风险匹配校验 + 余额扣减 + 持仓加仓（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_customer_profile import FinCustomerProfileRepo
from repositories.fin_holdings import FinHoldingsRepo
from repositories.fin_product import FinProductRepo
from schemas.holdings import HoldingResp
from schemas.purchase import PurchaseResp
from utils.exceptions import (
    ForbiddenError,
    NotFoundError,
    NotSuitableError,
    ParamError,
)

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

# 风险等级 → 序号。兼容两套口径：R1~R5 与 保守~激进（同一映射）。
_RISK_RANK = {
    "R1": 1, "R2": 2, "R3": 3, "R4": 4, "R5": 5,
    "保守": 1, "稳健": 2, "平衡": 3, "进取": 4, "激进": 5,
}


def _risk_rank(level: str | None) -> int | None:
    """客户画像 / 产品的风险等级统一转序号；未知返回 None。"""
    if not level:
        return None
    return _RISK_RANK.get(level.strip())


async def purchase(
    db: AsyncSession, user: SysUser, product_id: int, amount: Decimal
) -> PurchaseResp:
    """申购基金：校验通过后扣减余额并加仓，全程单事务。

    - 仅客户可申购；
    - 产品须在售且净值非空；
    - 客户风险等级序号 >= 产品风险等级序号，否则 1005 拦截；
    - 余额不足拦截；扣款 + 加仓要么都成、要么都回滚。
    """
    if user.user_type != "CUSTOMER":
        raise ForbiddenError("仅客户账号可申购")

    amount = amount.quantize(_MONEY, rounding=ROUND_HALF_UP)

    product = await FinProductRepo(db).get(product_id)
    if product is None:
        raise NotFoundError("产品不存在")
    if product.status != "在售":
        raise ParamError("产品不在售")
    if product.nav is None:
        raise ParamError("产品暂无净值，无法申购")

    profile = await FinCustomerProfileRepo(db).get_by_customer_id(user.id)
    customer_rank = _risk_rank(profile.risk_level if profile else None)
    if customer_rank is None:
        raise NotSuitableError("客户无风险等级，无法申购")
    product_rank = _risk_rank(product.risk_level)
    if product_rank is None or customer_rank < product_rank:
        raise NotSuitableError()

    shares = (amount / product.nav).quantize(_SHARES, rounding=ROUND_HALF_UP)

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

    try:
        if not await account_repo.deduct_balance(user.id, amount):
            raise ParamError("可用余额不足")
        await holdings_repo.upsert(user.id, product_id, shares, amount)
        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 PurchaseResp(
        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,
        ),
    )