"""
This is a software implementation of an approximation of the Szilagyi Waterspout Index. The calculated values of the SWI
are continuous. The wind-speed at 850 hPa is ignored as the nomogram dictates it as a simple on/off criterion.

There is only one function provided, so the use should be straight-forward. For example::

	>>> import szilagyi
	>>> round(szilagyi.calculate_swi(10.5, 24100), 3)
	0.811
	>>> round(szilagyi.calculate_swi(7, 12500), 3)
	-4.88
"""

from ._nomogram import calculate_swi as _calculate_swi
from ._nomogram import MAX_TEMPERATURE_DIFFERENCE, MAX_CONVECTIVE_CLOUD_DEPTH


def calculate_swi(temperature_difference, convective_cloud_depth):
	"""
	Calculates the Szilagyi Waterspout Index for *temperature_difference* and *convective_cloud_depth*. These are
	expected to be expressed in Celsius degrees and feet, respectively.

	Function will raise ValueError if one of the values is not in range of the original nomogram. The maximum values are
	available as MAX_TEMPERATURE_DIFFERENCE and MAX_CONVECTIVE_CLOUD_DEPTH constants.
	"""
	if temperature_difference < 0 or temperature_difference > MAX_TEMPERATURE_DIFFERENCE:
		raise ValueError(f"temperature_difference must be within <0, {MAX_TEMPERATURE_DIFFERENCE}> range")
	if convective_cloud_depth < 0 or convective_cloud_depth > MAX_CONVECTIVE_CLOUD_DEPTH:
		raise ValueError(f"convective_cloud_depth must be within <0, {MAX_CONVECTIVE_CLOUD_DEPTH}> range")
	return _calculate_swi(temperature_difference, convective_cloud_depth)