"""服务端生成日K+成交量 PNG，供大模型视觉解读。"""

import io
from datetime import datetime

from .kline_store import get_daily_candles


async def render_daily_chart_png_async(symbol: str, limit: int = 300) -> bytes:
    import matplotlib

    matplotlib.use("Agg")
    import matplotlib.pyplot as plt
    import matplotlib.dates as mdates

    candles, _ = await get_daily_candles(symbol, limit)
    if not candles:
        raise ValueError(f"no klines for {symbol}")

    times = [datetime.fromtimestamp(c["time"] / 1000) for c in candles]
    opens = [c["open"] for c in candles]
    highs = [c["high"] for c in candles]
    lows = [c["low"] for c in candles]
    closes = [c["close"] for c in candles]
    vols = [c.get("quote_volume") or c.get("volume") or 0 for c in candles]

    fig, (ax1, ax2) = plt.subplots(
        2, 1, figsize=(12, 7), gridspec_kw={"height_ratios": [3, 1]}, facecolor="#0d1118"
    )
    fig.subplots_adjust(hspace=0.08)

    for i in range(len(candles)):
        t = times[i]
        o, h, l, cl = opens[i], highs[i], lows[i], closes[i]
        color = "#0ecb81" if cl >= o else "#f6465d"
        ax1.plot([t, t], [l, h], color=color, linewidth=0.8)
        ax1.add_patch(
            plt.Rectangle(
                (mdates.date2num(t) - 0.3, min(o, cl)),
                0.6,
                abs(cl - o) or 0.001,
                facecolor=color,
                edgecolor=color,
            )
        )
    ax1.set_facecolor("#0d1118")
    ax1.tick_params(colors="#8b9cb3")
    ax1.set_title(f"{symbol} 日K + 成交量", color="#e7ecf3", fontsize=14)
    ax1.grid(True, alpha=0.2)

    colors_vol = ["#0ecb81" if closes[i] >= opens[i] else "#f6465d" for i in range(len(candles))]
    ax2.bar(times, vols, color=colors_vol, alpha=0.7, width=0.8)
    ax2.set_facecolor("#0d1118")
    ax2.tick_params(colors="#8b9cb3")
    ax2.set_ylabel("成交额", color="#8b9cb3")
    ax2.grid(True, alpha=0.2)

    for ax in (ax1, ax2):
        ax.xaxis.set_major_formatter(mdates.DateFormatter("%m-%d"))
    fig.autofmt_xdate()

    buf = io.BytesIO()
    fig.savefig(buf, format="png", dpi=120, facecolor="#0d1118")
    plt.close(fig)
    buf.seek(0)
    return buf.read()