"""K 线数据访问（从库读）。

写入由 DataProvider 适配器负责（阶段1 接 Tushare/AKShare）。
MVP 的数据由 synthetic.seed_if_empty 灌入。
"""
from __future__ import annotations

from datetime import datetime

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from ..models import Candle


async def get_candles(
    session: AsyncSession,
    symbol: str,
    timeframe: str = "1d",
    start: datetime | None = None,
    end: datetime | None = None,
    limit: int = 5000,
) -> list[Candle]:
    stmt = select(Candle).where(
        Candle.symbol == symbol,
        Candle.timeframe == timeframe,
    )
    if start is not None:
        stmt = stmt.where(Candle.ts >= start)
    if end is not None:
        stmt = stmt.where(Candle.ts <= end)
    stmt = stmt.order_by(Candle.ts.asc()).limit(limit)
    result = await session.execute(stmt)
    return list(result.scalars().all())