Source code for sunkit_spex.legacy.constants

"""
Class and code to easily switch between astropy constants and values taken directly from SSW for
comparison.
"""

from astropy import constants as const

__all__ = ["Constants"]

CONSTANTS = {
    "idl": {
        "mc2": 510.98,  # electron rest mass keV
        "clight": 2.9979e10,  # cm s^-1
        "au": 1.496e13,  # cm
        "r0": 2.8179e-13,  # classical electron radius cm
        "alpha": 7.29735308e-3,  # alpha
        "twoar02": 1.15893512e-27,  # 2 * alpha * r0^2
    },
    "astropy": {
        "mc2": (const.m_e * const.c**2).to("keV").value,
        "clight": const.c.cgs.value,
        "au": const.au.cgs.value,
        "r0": (const.a0 * const.alpha**2).cgs.value,
        "alpha": const.alpha.cgs.value,
        "twoar02": 2.0 * const.alpha.cgs.value * (const.a0 * const.alpha**2).cgs.value ** 2,
    },
}


class Singleton(type):
    """
    A singleton metaclass
    """

    _instances = {}

    def __call__(cls, *args, **kwargs):
        if cls not in cls._instances:
            cls._instances[cls] = super().__call__(*args, **kwargs)
        return cls._instances[cls]




class Constants(metaclass=Singleton):
    """
    Centralised constant representation
    """

    def __init__(self, ref="idl"):
        """

        Parameters
        ----------
        ref
        """
        self.ref = ref



    def get_constant(self, name):
        """
        Return the value of the constant.
        Parameters
        ----------
        name : str
            Name of constant

        Returns
        -------
        float
            Value of constant
        """
        if self.ref not in ["astropy", "idl"]:
            raise ValueError(f"Valid values for ref are astropy or idl not {self.ref}.")

        if name not in CONSTANTS[self.ref].keys():
            raise ValueError(f"Valid names are {CONSTANTS[self.ref].keys()} or idl not {name}.")

        return CONSTANTS[self.ref][name]