"""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 _safe_float_series(raw: list, n: int) -> list[float]:
    out: list[float] = []
    for i in range(n):
        if i >= len(raw):
            out.append(0.0)
            continue
        v = raw[i]
        try:
            out.append(float(v) if v is not None else 0.0)
        except (TypeError, ValueError):
            out.append(0.0)
    return out


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) >= 9:
        s = s[:7]
    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 == "dual_axis_line" and datasets and labels:
        ax2 = ax.twinx()
        x = list(range(len(labels)))
        step = max(1, len(labels) // 8)
        h1, l1 = [], []
        h2, l2 = [], []
        for i, ds in enumerate(datasets):
            y_raw = ds.get("data") or []
            if not y_raw:
                continue
            y = _safe_float_series(y_raw, len(labels))
            lab = ds.get("label") or f"Serie {i + 1}"
            col = _color_to_rgb(str(ds.get("borderColor") or ds.get("backgroundColor") or "#333333"))
            y_axis = str(ds.get("yAxisID") or "").lower()
            use_right = y_axis in ("right", "weight", "y1")
            use_left = not use_right
            target = ax if use_left else ax2
            linestyle = "--" if ds.get("borderDash") else "-"
            (ln,) = target.plot(
                x[: len(y)],
                y,
                label=lab,
                color=col,
                linewidth=1.8,
                linestyle=linestyle,
                marker="o",
                markersize=2 if linestyle == "-" else 0,
            )
            if use_left:
                h1.append(ln)
                l1.append(lab)
            else:
                h2.append(ln)
                l2.append(lab)
        ax.set_xticks(x[::step])
        ax.set_xticklabels([labels[j] for j in range(0, len(labels), step)], rotation=25, fontsize=7)
        ax.grid(True, alpha=0.25)
        ax.set_xmargin(0.02)
        leg = h1 + h2
        leg_l = l1 + l2
        if leg:
            ax.legend(leg, leg_l, loc="upper right", fontsize=7)

    elif chart_type == "bar" and datasets and labels:
        n = len(labels)
        x = list(range(n))
        stack_keys_nonnull = [ds.get("stack") for ds in datasets if (ds.get("data") or []) != []]
        use_stacked = (
            len(datasets) >= 2
            and len(stack_keys_nonnull) == len(datasets)
            and all(sk for sk in stack_keys_nonnull)
            and len(set(stack_keys_nonnull)) == 1
        )
        if use_stacked:
            bottom = [0.0] * n
            for ds in datasets:
                y_raw = ds.get("data") or []
                yv = _safe_float_series(y_raw, n)
                lab = ds.get("label") or "Serie"
                col = _color_to_rgb(str(ds.get("backgroundColor") or ds.get("borderColor") or "#1D9E75"))
                ax.bar(x, yv, bottom=bottom, label=lab, color=col, alpha=0.9, width=0.72)
                bottom = [bottom[i] + yv[i] for i in range(n)]
            ax.set_xticks(x)
            ax.set_xticklabels(labels, rotation=30, fontsize=7)
        else:
            width = 0.8 / max(len(datasets), 1)
            for i, ds in enumerate(datasets):
                y_raw = ds.get("data") or []
                yv = _safe_float_series(y_raw, n)
                offset = (i - len(datasets) / 2 + 0.5) * width
                xpos = [xj + offset for xj in x]
                lab = ds.get("label") or f"Serie {i + 1}"
                col = _color_to_rgb(str(ds.get("backgroundColor") or ds.get("borderColor") or "#1D9E75"))
                ax.bar(xpos, yv, width=width * 0.9, label=lab, color=col, alpha=0.88)
            ax.set_xticks(x)
            ax.set_xticklabels(labels, rotation=30, fontsize=7)
        ax.legend(loc="upper right", fontsize=7)
        ax.grid(True, axis="y", alpha=0.25)
        ax.set_xmargin(0.02)

    elif chart_type in ("line", "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"))
            ls = "--" if ds.get("borderDash") else "-"
            ax.plot(
                list(x)[: len(y)],
                y,
                label=lab,
                color=col,
                linewidth=1.6,
                linestyle=ls,
                marker="o",
                markersize=2,
            )
        if labels:
            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)
        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()