# core/tools/build_glucose_plot.py
from __future__ import annotations

import io
from datetime import datetime, timedelta
from typing import List, Dict, Any, Tuple

import matplotlib
matplotlib.use("Agg")  # Headless für HF
import matplotlib.pyplot as plt

from core.tools.nightscout import get_sgv_entries


def _parse_entries(entries: List[Dict[str, Any]]) -> Tuple[List[datetime], List[int]]:
    times: List[datetime] = []
    values: List[int] = []

    for e in entries or []:
        sgv = e.get("sgv")
        ts = e.get("date")  # ms epoch
        if sgv is None or ts is None:
            continue
        try:
            times.append(datetime.utcfromtimestamp(float(ts) / 1000.0))
            values.append(int(float(sgv)))
        except Exception:
            continue

    return times, values


def build_glucose_plot_png(hours: int = 3) -> bytes:
    """
    PNG Glukoseverlauf der letzten `hours`.

    Zielbereich: 80–180 (grün)
    Zonen:
      < 80        rot
      80–95       gelb
      95–180      grün
      180–250     gelb
      > 250       rot
    """
    # ---- Nightscout Daten ----
    entries: List[Dict[str, Any]] = get_sgv_entries(hours=hours)  # <<< WICHTIG: hours=..., nicht since_hours
    if not entries:
        raise RuntimeError("No Nightscout data available")

    times, values = _parse_entries(entries)
    if not times:
        raise RuntimeError("No valid SGV points")

    # ---- Plot ----
    fig, ax = plt.subplots(figsize=(9, 4.8))

    # Achsenhintergrund explizit weiß (verhindert "alles blau" durch Styles)
    ax.set_facecolor("white")
    fig.patch.set_facecolor("white")

    # Y-Limits so, dass alle Zonen sichtbar sind
    ymin = min(40, min(values) - 20)
    ymax = max(300, max(values) + 20)
    ax.set_ylim(ymin, ymax)

    # Deutlichere Farben + höheres Alpha (Telegram komprimiert!)
    RED = "#ff6b6b"
    YELLOW = "#ffd166"
    GREEN = "#2ecc71"

    # Zonen (zorder klein -> liegen "hinten")
    ax.axhspan(ymin, 80,   facecolor=RED,    alpha=0.35, zorder=0)
    ax.axhspan(80, 95,    facecolor=YELLOW, alpha=0.35, zorder=0)
    ax.axhspan(95, 180,   facecolor=GREEN,  alpha=0.28, zorder=0)
    ax.axhspan(180, 250,  facecolor=YELLOW, alpha=0.35, zorder=0)
    ax.axhspan(250, ymax, facecolor=RED,    alpha=0.35, zorder=0)

    # Zielbereich als dünne Kontur (hilft visuell)
    ax.axhline(80,  linewidth=1, alpha=0.4, zorder=1)
    ax.axhline(180, linewidth=1, alpha=0.4, zorder=1)

    # Verlauf (zorder hoch -> immer sichtbar oben)
    ax.plot(times, values, linewidth=2.2, marker="o", markersize=3.2, zorder=5)

    ax.set_ylabel("mg/dL")
    ax.set_title(f"Glukoseverlauf – letzte {hours}h (Ziel: 80–180)")
    ax.grid(True, alpha=0.25, zorder=2)
    fig.autofmt_xdate()

    buf = io.BytesIO()
    plt.tight_layout()
    plt.savefig(buf, format="png", dpi=140)
    plt.close(fig)
    buf.seek(0)
    return buf.read()