"""Example of a composable curve deformation loaded with --plugin."""
import math
from spatial_lab.kernel import register_operator

@register_operator('wave-z', version=1, inputs=('path',),
                   description='Displace a curve along world Z by a sinusoid of world X.')
def wave_z(context, params, inputs):
    path = inputs['path']
    if path['kind'] != 'curve':
        raise ValueError('wave-z requires a curve')
    amplitude = context.number(params.get('amplitude', 1))
    wavelength = context.number(params.get('wavelength', 6))
    if wavelength <= 0:
        raise ValueError('wavelength must be positive')
    points = [[x, y, z + amplitude * math.sin(math.tau * x / wavelength)]
              for x, y, z in path['points']]
    return {'kind': 'curve', 'points': points, 'closed': path['closed']}