"""Region image of a converted drawing (DXF) for the "도면 보기" links of the candidate tables (stage C, 2026-10-19).

The same drawing code as the reading aid Code/울산P1판독/dxftools.render, parameterised by a DXF path. Entities that touch the region are drawn
black on white; Korean text shows as boxes (no font mapping), numbers are readable.
"""
import ezdxf
from ezdxf import bbox


def _in_region(e, x0, y0, x1, y1):
    try:
        b = bbox.extents([e], fast=True)
    except Exception:
        return False
    return b.has_data and b.extmax.x >= x0 and b.extmin.x <= x1 and b.extmax.y >= y0 and b.extmin.y <= y1


def render(dxf_path, cx, cy, half, out_png, px=1400, mark=True):
    """PNG of the square [cx-half, cx+half] x [cy-half, cy+half]; a ring marks the point (cx, cy)."""
    import matplotlib
    matplotlib.use("Agg")
    import matplotlib.pyplot as plt
    from ezdxf.addons.drawing import Frontend, RenderContext
    from ezdxf.addons.drawing.config import BackgroundPolicy, ColorPolicy, Configuration
    from ezdxf.addons.drawing.matplotlib import MatplotlibBackend
    doc = ezdxf.readfile(dxf_path)
    x0, x1, y0, y1 = cx - half, cx + half, cy - half, cy + half
    keep = [e for e in doc.modelspace() if _in_region(e, x0, y0, x1, y1)]
    fig = plt.figure(figsize=(px / 100, px / 100), dpi=100)
    ax = fig.add_axes([0, 0, 1, 1])
    cfg = Configuration(background_policy=BackgroundPolicy.WHITE, color_policy=ColorPolicy.BLACK)
    Frontend(RenderContext(doc), MatplotlibBackend(ax), config=cfg).draw_entities(keep)
    if mark:
        ax.add_patch(plt.Circle((cx, cy), half * 0.04, fill=False, color="red", linewidth=2))
    ax.set_xlim(x0, x1)
    ax.set_ylim(y0, y1)
    ax.set_aspect("equal")
    ax.axis("off")
    fig.savefig(out_png, facecolor="white")
    plt.close(fig)
    return out_png