"""E - 历史交锋切片: 交手史与胜负规律(h2h)。"""
from __future__ import annotations

from typing import TYPE_CHECKING

from sqlalchemy import select
from sqlalchemy.orm import selectinload

from src.db.base import AsyncSessionLocal
from src.db.models import Match
from src.llm.slices.common import MatchHeader, SliceResult

if TYPE_CHECKING:
    from sqlalchemy.ext.asyncio import AsyncSession


async def h2h_slice(header: MatchHeader, *, limit: int = 8, before=None, db: AsyncSession | None = None) -> SliceResult:
    """E - 历史交锋切片: 过去数年 + 近期交手数据,提取交手规律。before=match_date 用于回测。

    db: 可选共享 session,避免每个切片独立建连(见 context_builder 模块 docstring)。
    """
    if db is not None:
        h2h = await _get_h2h(db, header.home_team_id, header.away_team_id, before=before, limit=limit)
    else:
        async with AsyncSessionLocal() as new_db:
            h2h = await _get_h2h(new_db, header.home_team_id, header.away_team_id, before=before, limit=limit)
    lines = [f"── 历史交锋(近 {limit} 次) ──"]
    n_with_score = 0
    if h2h:
        # 从当前主队视角统计:判断当前主队在每场交锋中是主是客
        current_home_wins = current_home_draws = current_home_losses = 0
        for hm in h2h:
            d = hm.match_date.strftime("%Y-%m") if hm.match_date else "?"
            if hm.home_goals is not None:
                n_with_score += 1
                # 判断当前主队当时是主队还是客队
                if hm.home_team_id == header.home_team_id:
                    # 当前主队当时是主队
                    if hm.home_goals > hm.away_goals:
                        current_home_wins += 1
                    elif hm.home_goals == hm.away_goals:
                        current_home_draws += 1
                    else:
                        current_home_losses += 1
                else:
                    # 当前主队当时是客队(从客队视角看赛果)
                    if hm.away_goals > hm.home_goals:
                        current_home_wins += 1
                    elif hm.away_goals == hm.home_goals:
                        current_home_draws += 1
                    else:
                        current_home_losses += 1
                lines.append(f"  {d}: {hm.home_team.name} {hm.home_goals}-{hm.away_goals} {hm.away_team.name}")
            else:
                lines.append(f"  {d}: {hm.home_team.name} vs {hm.away_team.name} (无比分)")
        total = current_home_wins + current_home_draws + current_home_losses
        if total:
            lines.append(
                f"  总计 {total} 场(从当前主队 {header.home_name} 视角): "
                f"{current_home_wins}胜 {current_home_draws}平 {current_home_losses}负"
            )
    else:
        lines.append("  无数据")
    # has_data 以「有比分的交锋」为准:仅有对阵无比分时不足以支撑分析
    return SliceResult(text="\n".join(lines), has_data=n_with_score > 0, n_records=n_with_score)


async def _get_h2h(db, home_id: int, away_id: int, before, *, limit: int = 5) -> list[Match]:
    """两队交锋史。需预加载 home_team / away_team(切片输出队名)。"""
    stmt = (
        select(Match)
        .options(
            selectinload(Match.home_team),
            selectinload(Match.away_team),
        )
        .where(Match.match_status == "finished")
        .where(Match.home_goals.is_not(None))
        .where(
            ((Match.home_team_id == home_id) & (Match.away_team_id == away_id))
            | ((Match.home_team_id == away_id) & (Match.away_team_id == home_id))
        )
        .order_by(Match.match_date.desc())
        .limit(limit)
    )
    if before is not None:
        stmt = stmt.where(Match.match_date < before)
    result = await db.execute(stmt)
    return list(result.scalars().all())