"""
Vektorisierung: PNG → Pfade via potrace.
Zerlegt das Bitmap in Konturen, die dann als SVG-Pfade manipuliert werden können.
"""
from __future__ import annotations

import numpy as np

try:
    import potracer
    HAS_POTRACER = True
except ImportError:
    HAS_POTRACER = False

from svgpathtools import Path as SvgPath, CubicBezier, Line
from core.logo_model import GlyphGroup


def _rgba_to_bitmap(pixels: np.ndarray, threshold: int = 128) -> np.ndarray:
    """Konvertiert RGBA in ein Schwarz/Weiß-Bitmap für potrace."""
    gray = np.mean(pixels[:, :, :3], axis=2)
    alpha = pixels[:, :, 3] / 255.0
    effective = gray * alpha + 255 * (1 - alpha)
    return (effective < threshold).astype(np.uint8)


def _curve_to_svg_segment(segment):
    """Konvertiert ein potrace-Kurvensegment in ein svgpathtools-Segment."""
    tag = segment.tag
    c = segment.c
    end = segment.end_point

    if tag == potracer.CORNER:
        return [
            Line(complex(c[0][0], c[0][1]), complex(c[1][0], c[1][1])),
            Line(complex(c[1][0], c[1][1]), complex(end[0], end[1])),
        ]
    else:
        start_pt = complex(c[0][0], c[0][1])
        cp1 = complex(c[0][0], c[0][1])
        cp2 = complex(c[1][0], c[1][1])
        end_pt = complex(end[0], end[1])
        return [CubicBezier(start_pt, cp1, cp2, end_pt)]


def trace_to_paths(
    pixels: np.ndarray,
    threshold: int = 128,
    turd_size: int = 2,
    alpha_max: float = 1.0,
) -> list[GlyphGroup]:
    """
    Hauptfunktion: Konvertiert ein RGBA-Bild in eine Liste von GlyphGroups.
    Jede zusammenhängende Kontur wird eine eigene Gruppe.
    """
    if not HAS_POTRACER:
        raise ImportError(
            "potracer ist nicht installiert. "
            "Bitte 'pip install potracer' ausführen."
        )

    bitmap = _rgba_to_bitmap(pixels, threshold)
    bmp = potracer.Bitmap(bitmap)
    path_result = bmp.trace(
        turdsize=turd_size,
        alphamax=alpha_max,
    )

    groups: list[GlyphGroup] = []
    for i, curve in enumerate(path_result):
        svg_segments = []
        for segment in curve.segments:
            svg_segments.extend(_curve_to_svg_segment(segment))

        if not svg_segments:
            continue

        svg_path = SvgPath(*svg_segments)
        bbox = svg_path.bbox()  # xmin, xmax, ymin, ymax

        group = GlyphGroup(
            label=f"Pfad_{i}",
            paths=[svg_path],
            bbox=(bbox[0], bbox[2], bbox[1] - bbox[0], bbox[3] - bbox[2]),
        )
        groups.append(group)

    return groups