"""fin_account 仓储：按客户 ID 取资金账户 + 余额加减（原子 UPDATE）。

注：本表主键为 customer_id（非 id），故不复用 BaseRepository.delete/count 中的 id 约定。
余额增减用原子 UPDATE（balance = balance ± delta）防并发丢更新，不依赖乐观锁重试。
"""
from __future__ import annotations

from decimal import Decimal

from sqlalchemy import select, update

from model.fin_account import FinAccount
from repositories.base import BaseRepository


class FinAccountRepo(BaseRepository):
    model = FinAccount

    async def get_by_customer_id(self, customer_id: int) -> FinAccount | None:
        return await self.db.scalar(
            select(FinAccount).where(FinAccount.customer_id == customer_id)
        )

    async def create(self, customer_id: int, balance: Decimal) -> FinAccount:
        """开资金户（充值时账户不存在则自动开户入账）。"""
        account = FinAccount(customer_id=customer_id, balance=balance)
        self.db.add(account)
        await self.db.commit()
        await self.db.refresh(account)
        return account

    async def add_balance(self, customer_id: int, delta: Decimal) -> FinAccount:
        """入账：balance += delta，原子自增后回读最新余额。"""
        await self.db.execute(
            update(FinAccount)
            .where(FinAccount.customer_id == customer_id)
            .values(
                balance=FinAccount.balance + delta,
                version=FinAccount.version + 1,
            )
        )
        await self.db.commit()
        return await self.get_by_customer_id(customer_id)

    async def subtract_balance(
        self, customer_id: int, delta: Decimal
    ) -> FinAccount | None:
        """出账：balance -= delta，可用余额（balance - frozen_amount）不足时返回 None。"""
        result = await self.db.execute(
            update(FinAccount)
            .where(
                FinAccount.customer_id == customer_id,
                FinAccount.balance - FinAccount.frozen_amount >= delta,
            )
            .values(
                balance=FinAccount.balance - delta,
                version=FinAccount.version + 1,
            )
        )
        await self.db.commit()
        if result.rowcount == 0:
            return None
        return await self.get_by_customer_id(customer_id)

    async def deduct_balance(self, customer_id: int, delta: Decimal) -> bool:
        """申购事务内扣款：balance -= delta（可用余额不足则不动）。

        不 commit，由 service 层事务统一提交，保证「扣款 + 加仓」原子性。
        可用余额（balance - frozen_amount）不足时返回 False。
        """
        result = await self.db.execute(
            update(FinAccount)
            .where(
                FinAccount.customer_id == customer_id,
                FinAccount.balance - FinAccount.frozen_amount >= delta,
            )
            .values(
                balance=FinAccount.balance - delta,
                version=FinAccount.version + 1,
            )
        )
        return result.rowcount > 0

    async def credit_balance(self, customer_id: int, delta: Decimal) -> bool:
        """赎回事务内入账：balance += delta。

        不 commit，由 service 层事务统一提交，保证「减仓 + 入账」原子性。
        """
        result = await self.db.execute(
            update(FinAccount)
            .where(FinAccount.customer_id == customer_id)
            .values(
                balance=FinAccount.balance + delta,
                version=FinAccount.version + 1,
            )
        )
        return result.rowcount > 0