"""
Split a DXF drawing by layer
============================

Use the ``.cad`` accessor to fan a single :class:`pyvista.PolyData`
back out into a :class:`pyvista.MultiBlock` keyed by layer name. Each
block contains only the cells originally drawn on that layer.

This example uses a real multi-layer DXF from the ezdxf project (MIT)
with entities on layers ``0``, ``BLUE``, ``RED``, so the layer split
is non-trivial, exactly what you face on a real PCB or architectural
DXF.
"""

# %%

import pandas as pd
import pyvista as pv

import pyvista_cad
from pyvista_cad.examples import downloads

# %%
# Read the real drawing.

drawing = pyvista_cad.read_dxf(downloads.dxf_drawing_path())
drawing

# %%
# Split by layer. Each child :class:`~pyvista.PolyData` keeps the
# ``cad.layer`` cell-data array so further reshuffles round-trip.

by_layer = drawing.cad.split_by_layer()
pd.DataFrame(
    [
        {'layer': name, 'cells': block.n_cells}
        for name, block in zip(by_layer.keys(), by_layer)
        if block is not None
    ]
)

# %%
# Render each layer with its own color so the drawing's logical
# structure is immediately visible.

pl = pv.Plotter()
palette = ['steelblue', 'indianred', 'goldenrod', 'mediumseagreen', 'orchid', 'slategray']
for i, (name, block) in enumerate(zip(by_layer.keys(), by_layer)):
    if block is None or block.n_cells == 0:
        continue
    pl.add_mesh(block, color=palette[i % len(palette)], line_width=2, label=str(name))
pl.add_legend()
pl.view_xy()
pl.show()