from __future__ import annotations

from dataclasses import dataclass, field
from statistics import mean

from .candle_rows import rows_to_hlc


@dataclass
class BtcDailyGateResult:
    """BTC 日线辅助门控（非产品主线）：下跌不扫山寨，其它仍扫 —— 仅 downtrend 时关闭本轮 alt K 线请求。"""

    allow_alt_scan: bool
    regime: str  # sideways | downtrend | neutral_or_up | unknown
    reason: str
    metrics: dict = field(default_factory=dict)


def evaluate_btc_daily_gate(
    btc_1d_rows: list[list[str]],
    *,
    sideways_lookback_days: int = 14,
    sideways_max_range_pct: float = 10.0,
    min_bars: int = 30,
) -> BtcDailyGateResult:
    """
    原则：下跌不扫，其它都扫。

    - 下跌（唯一不扫）：非横盘，且收盘低于近 20 日收盘均线，且该均线相对前一段走低。
    - 其余（横盘、上涨、宽幅震荡、数据不足 unknown 等）：一律允许扫山寨。
    """
    ah, al, ac = rows_to_hlc(btc_1d_rows)

    if len(ac) < min_bars:
        return BtcDailyGateResult(
            allow_alt_scan=True,
            regime="unknown",
            reason=f"insufficient_1d_bars have={len(ac)} need>={min_bars}, gate skipped",
            metrics={"have": len(ac), "min_bars": min_bars},
        )

    lb = max(5, min(sideways_lookback_days, len(ah) - 1))
    window_h = ah[-lb:]
    window_l = al[-lb:]
    range_high = max(window_h)
    range_low = min(window_l)
    mid = (range_high + range_low) / 2 if range_high > range_low else 0.0
    range_pct = ((range_high - range_low) / mid) * 100 if mid > 0 else 999.0

    sma_curr = mean(ac[-20:])
    sma_prev = mean(ac[-26:-6]) if len(ac) >= 26 else sma_curr

    last_close = ac[-1]
    is_sideways = range_pct <= sideways_max_range_pct

    if is_sideways:
        return BtcDailyGateResult(
            allow_alt_scan=True,
            regime="sideways",
            reason="btc_daily_sideways",
            metrics={
                "range_lookback_days": lb,
                "range_pct": round(range_pct, 4),
                "sideways_max_range_pct": sideways_max_range_pct,
                "last_close": last_close,
                "sma20": round(sma_curr, 6),
                "sma20_prev_block": round(sma_prev, 6),
            },
        )

    is_downtrend = last_close < sma_curr and sma_curr < sma_prev
    if is_downtrend:
        return BtcDailyGateResult(
            allow_alt_scan=False,
            regime="downtrend",
            reason="btc_daily_downtrend_below_falling_sma20",
            metrics={
                "range_lookback_days": lb,
                "range_pct": round(range_pct, 4),
                "sideways_max_range_pct": sideways_max_range_pct,
                "last_close": last_close,
                "sma20": round(sma_curr, 6),
                "sma20_prev_block": round(sma_prev, 6),
            },
        )

    return BtcDailyGateResult(
        allow_alt_scan=True,
        regime="neutral_or_up",
        reason="btc_not_sideways_not_downtrend_gate_open",
        metrics={
            "range_lookback_days": lb,
            "range_pct": round(range_pct, 4),
            "last_close": last_close,
            "sma20": round(sma_curr, 6),
            "sma20_prev_block": round(sma_prev, 6),
        },
    )