"""Chart.js-ähnliche Payloads → PNG (Matplotlib). Von PDF- und Bundle-Rendering gemeinsam genutzt."""
from __future__ import annotations

import io
from typing import Any

import matplotlib

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


def _color_to_rgb(hex_or_rgba: str) -> tuple[float, float, float]:
    s = (hex_or_rgba or "#333333").strip()
    if s.startswith("#") and len(s) >= 7:
        try:
            r = int(s[1:3], 16) / 255.0
            g = int(s[3:5], 16) / 255.0
            b = int(s[5:7], 16) / 255.0
            return (r, g, b)
        except ValueError:
            pass
    return (0.12, 0.62, 0.46)


def chart_payload_to_png(payload: dict[str, Any], fig_width_in: float = 6.2, fig_height_in: float = 3.4) -> bytes:
    chart_type = payload.get("chart_type") or "line"
    data = payload.get("data") or {}
    labels = data.get("labels") or []
    datasets = data.get("datasets") or []

    fig, ax = plt.subplots(figsize=(fig_width_in, fig_height_in), dpi=120)
    ax.set_facecolor("#fafaf9")
    fig.patch.set_facecolor("#ffffff")

    if chart_type == "pie" and datasets:
        ds0 = datasets[0]
        values = ds0.get("data") or []
        colors = ds0.get("backgroundColor") or ["#1D9E75", "#378ADD", "#D85A30"]
        if labels and values and len(labels) == len(values):
            ax.pie(values, labels=labels, autopct="%1.0f%%", colors=colors[: len(values)], startangle=90)
            ax.axis("equal")
        else:
            ax.text(0.5, 0.5, "Keine Daten", ha="center", va="center", transform=ax.transAxes)

    elif chart_type in ("line", "bar", "scatter") and datasets:
        x = range(len(labels)) if labels else []
        for i, ds in enumerate(datasets):
            y = ds.get("data") or []
            if not y:
                continue
            lab = ds.get("label") or f"Serie {i + 1}"
            col = _color_to_rgb(str(ds.get("borderColor") or ds.get("backgroundColor") or "#1D9E75"))
            if chart_type == "bar":
                yv = y[: len(labels)] if labels else y
                bg = ds.get("backgroundColor")
                if isinstance(bg, list):
                    cols = [_color_to_rgb(str(c)) for c in bg[: len(yv)]]
                else:
                    cols = [_color_to_rgb(str(bg or "#1D9E75"))] * len(yv)
                ax.bar(list(range(len(yv))), yv, label=lab, color=cols[: len(yv)], alpha=0.88)
            else:
                ax.plot(
                    list(x)[: len(y)],
                    y,
                    label=lab,
                    color=col,
                    linewidth=1.6,
                    marker="o",
                    markersize=2,
                )
        if labels and chart_type != "bar":
            step = max(1, len(labels) // 8)
            ax.set_xticks(list(x)[::step])
            ax.set_xticklabels([labels[j] for j in range(0, len(labels), step)], rotation=25, fontsize=7)
        elif labels and chart_type == "bar":
            ax.set_xticks(list(x))
            ax.set_xticklabels(labels, rotation=30, fontsize=7)
        ax.legend(loc="upper right", fontsize=7)
        ax.grid(True, alpha=0.25)
        ax.set_xmargin(0.02)

    else:
        ax.text(0.5, 0.5, "Diagrammtyp nicht unterstützt oder leer", ha="center", va="center", transform=ax.transAxes)

    fig.tight_layout()
    buf = io.BytesIO()
    fig.savefig(buf, format="png", bbox_inches="tight", facecolor=fig.get_facecolor())
    plt.close(fig)
    buf.seek(0)
    return buf.read()