"""
Basic utility functions for relationships between various profile related parameters.
"""
import numpy as np
import unyt as u

from cluster_generator.utils import mue



[docs]
def f_gas(M500, hubble=0.7):
    """
    Use the relationship between M500 and f_gas = Mgas/Mtot
    within r500 from Vikhlinin, A., et al. 2009, ApJ,
    692, 1033 (https://ui.adsabs.harvard.edu/abs/2009ApJ...692.1033V/).

    Parameters
    ----------
    M500 : float
        The M500 of the cluster in units of Msun.
    hubble : float, optional
        The Hubble parameter in units of 100 km/s/Mpc.
        Default: 0.7

    Returns
    -------
    f_gas at r500

    """
    m = M500 * 1.0e-15 / hubble
    return ((0.72 / hubble) ** 1.5) * (0.125 + 0.037 * np.log10(m))




[docs]
def m_bcg(M500):
    """
    Compute the total BCG mass given an :math:`M_{500}` value.

    Parameters
    ----------
    M500: float or :py:class:`unyt.array.unyt_quantity`
        The :math:`M_{500}` value of the BCG.

    Returns
    -------
    The total mass of the BCG.

    """
    x = np.log10(M500) - 14.5
    y = 0.39 * x + 12.15
    return 10**y




[docs]
def m_sat(M500):
    """
    TODO: Fact check!

    Parameters
    ----------
    M500: float or :py:class:`unyt.array.unyt_quantity`
        The :math:`M_{500}` value of the satellite.

    Returns
    -------
    The total mass of the satellite.

    """
    x = np.log10(M500) - 14.5
    y = 0.87 * x + 12.42
    return 10**y




[docs]
def rho_scale_hern(M, rs):
    """
    Returns the correct scale density for a total density and scale length.

    Parameters
    ----------
    M: float
        The total mass
    rs: float
        The scale radius

    Returns
    -------
    float
    """
    return M / (2 * np.pi * rs**3)




[docs]
def r_bcg(r200):
    """
    Compute the BCG radius given some r200 value.

    Parameters
    ----------
    r200: float
        The r200 value.

    Returns
    -------
    The BCG radius.

    """
    x = np.log10(r200) - 1.0
    y = 0.95 * x - 0.3
    return 10**y




[docs]
def convert_ne_to_density(ne):
    """
    Convert the electron density to a true density given the mean molecular mass parameter is
    the standard ~1.6.

    Parameters
    ----------
    ne: :py:class:`unyt.array.unyt_array` or :py:class:`unyt.array.unyt_quantity`
        The electron density array.

    Returns
    -------
    :py:class:`unyt.array.unyt_array` or :py:class:`unyt.array.unyt_quantity`
        The resulting conversion

    """
    ne = ne * u.cm**-3
    return ne.to_value("Msun/kpc**3", "number_density", mu=mue)