"""A 股撮合纯函数（match_session / 费率 / 100 股 / 封板）。

match_bar 必须是 raw 价格（spec §3.3 / §6.2）。所有费率来自 AccountConfig。
拒单返回 PaperReject；成交返回 PaperTrade。
资金检查由 Account 在 apply 前负责（matcher 不看资金）。
"""
import pandas as pd

from .limit import is_locked_for_buy_symbol, is_locked_for_sell_symbol
from .models import (
    AccountConfig,
    MatchSession,
    OrderSide,
    PaperOrder,
    PaperReject,
    PaperTrade,
)

MIN_LOT = 100


def cross_order(
    order: PaperOrder,
    match_bar: pd.Series,
    prev_close_raw: float,
    cfg: AccountConfig,
    is_st: bool = False,
) -> PaperTrade | PaperReject:
    """单笔订单撮合。

    步骤：
      1. 涨跌停封板拒单（raw，按板块幅度）
      2. 成交价（NEXT_OPEN=bar.open / CURRENT_CLOSE=bar.close）
      3. 限价单触价检查
      4. 100 股取整（买入向下取整；卖出允许零股）
      5. 费用（佣金 min 5 元 / 印花税仅卖 / 过户费单边）
    """
    symbol = order.symbol
    bar_date = str(match_bar.get("date", ""))

    # 1. 涨跌停封板拒单（raw）
    if order.side == OrderSide.BUY and is_locked_for_buy_symbol(
        match_bar, symbol, prev_close_raw, cfg, is_st
    ):
        return PaperReject(order.strategy_id, symbol, "limit_up_locked", bar_date)
    if order.side == OrderSide.SELL and is_locked_for_sell_symbol(
        match_bar, symbol, prev_close_raw, cfg, is_st
    ):
        return PaperReject(order.strategy_id, symbol, "limit_down_locked", bar_date)

    # 2. 成交价（按 match_session）
    if order.match_session == MatchSession.NEXT_OPEN:
        fill_price = match_bar["open"]
    elif order.match_session == MatchSession.CURRENT_CLOSE:
        fill_price = match_bar["close"]
    else:
        return PaperReject(
            order.strategy_id, symbol, "unsupported_match_session", bar_date
        )

    # 3. 限价单触价
    if not order.is_market:
        if order.side == OrderSide.BUY and fill_price > order.price:
            return PaperReject(order.strategy_id, symbol, "limit_not_touched", bar_date)
        if order.side == OrderSide.SELL and fill_price < order.price:
            return PaperReject(order.strategy_id, symbol, "limit_not_touched", bar_date)

    # 4. 100 股取整（买入向下取整；卖出不取整，允许零股退出）
    volume = order.volume
    if order.side == OrderSide.BUY:
        volume = (volume // MIN_LOT) * MIN_LOT
        if volume < MIN_LOT:
            return PaperReject(order.strategy_id, symbol, "volume_below_min_lot", bar_date)

    # 5. 费用
    gross = volume * fill_price
    commission = max(gross * cfg.rate, cfg.min_commission)
    stamp_duty = gross * cfg.stamp_duty_rate if order.side == OrderSide.SELL else 0.0
    transfer_fee = gross * cfg.transfer_fee_rate   # 单边；Account 算双向 ×2

    return PaperTrade(
        strategy_id=order.strategy_id,
        symbol=symbol,
        side=order.side,
        price=fill_price,
        volume=volume,
        commission=commission,
        stamp_duty=stamp_duty,
        transfer_fee=transfer_fee,
        bar_date=bar_date,
        match_session=order.match_session,
    )