__author__ = 'sibirrer'

import numpy as np
from scipy.interpolate import interp1d
import lenstronomy.GalKin.velocity_util as vel_util
from lenstronomy.GalKin.cosmo import Cosmo
from lenstronomy.GalKin.anisotropy import Anisotropy
from lenstronomy.LensModel.Profiles.spp import SPP
import lenstronomy.Util.constants as const
import math

__all__ = ['AnalyticKinematics']


class AnalyticKinematics(Anisotropy):
    """
    class to compute eqn 20 in Suyu+2010 with a Monte-Carlo from rendering from the
    light profile distribution and displacing them with a Gaussian seeing convolution.

    This class assumes spherical symmetry in light and mass distribution and
        - a Hernquist light profile (parameterised by the half-light radius)
        - a power-law mass profile (parameterized by the Einstein radius and logarithmic slop)

    The analytic equations for the kinematics in this approximation are presented e.g. in Suyu et al. 2010 and
    the spectral rendering approach to compute the seeing convolved slit measurement is presented in Birrer et al. 2016.
    The stellar anisotropy is parameterised based on Osipkov 1979; Merritt 1985.

    WARNING!!! Only supports Osipkov-Merritt anisotropy for now!

    All units are meant to be in angular arc seconds. The physical units are fold in through the angular diameter
    distances

    """
    def __init__(self, kwargs_cosmo, interpol_grid_num=100, log_integration=False, max_integrate=100,
                 min_integrate=0.001):
        """

        :param kwargs_cosmo: keyword argument with angular diameter distances entering the Galkin.cosmo class
        :param interpol_grid_num: number of interpolations in radius to compute radial velocity dispersion
        :param log_integration: perform numerical integration in logarithmic space
        :param max_integrate: maximum radius of integration (in projected arc seconds)
        :param min_integrate: minimum drawing/calculation of velocity dispersion (in projected arc seconds)
        """

        self._interp_grid_num = interpol_grid_num
        self._log_int = log_integration
        self._max_integrate = max_integrate  # maximal integration (and interpolation) in units of arcsecs
        self._min_integrate = min_integrate  # min integration (and interpolation) in units of arcsecs
        self._max_interpolate = max_integrate  # we chose to set the interpolation range to the integration range
        self._min_interpolate = min_integrate  # we chose to set the interpolation range to the integration range

        self._cosmo = Cosmo(**kwargs_cosmo)
        self._spp = SPP()
        Anisotropy.__init__(self, anisotropy_type='OM')

    def _rho0_r0_gamma(self, theta_E, gamma):
        # equation (14) in Suyu+ 2010
        return -1 * math.gamma(gamma/2) / (np.sqrt(np.pi)*math.gamma((gamma-3)/2.)) * theta_E ** gamma / \
               self._cosmo.arcsec2phys_lens(theta_E) * self._cosmo.epsilon_crit * const.M_sun / const.Mpc ** 3

    @staticmethod
    def draw_light(kwargs_light):
        """

        :param kwargs_light: keyword argument (list) of the light model
        :return: 3d radius (if possible), 2d projected radius, x-projected coordinate, y-projected coordinate
        """
        if 'a' not in kwargs_light:
            kwargs_light['a'] = 0.551 * kwargs_light['r_eff']
        a = kwargs_light['a']
        r = vel_util.draw_hernquist(a)
        R, x, y = vel_util.project2d_random(r)
        return r, R, x, y

    def _sigma_s2(self, r, R, r_ani, a, gamma, rho0_r0_gamma):
        """
        projected velocity dispersion
        :param r: 3d radius of the light tracer particle
        :param R: 2d projected radius of the light tracer particle
        :param r_ani: anisotropy radius
        :param a: scale of the Hernquist light profile
        :param gamma: power-law slope of the mass profile
        :param rho0_r0_gamma: combination of Einstein radius and power-law slope as equation (14) in Suyu+ 2010
        :return: projected velocity dispersion
        """
        beta = self.beta_r(r, **{'r_ani': r_ani})
        return (1 - beta * R**2/r**2) * self._sigma_r2_interp(r, a, gamma, rho0_r0_gamma, r_ani)

    def sigma_s2(self, r, R, kwargs_mass, kwargs_light, kwargs_anisotropy):
        """
        returns unweighted los velocity dispersion for a specified projected radius, with weight 1

        :param r: 3d radius (not needed for this calculation)
        :param R: 2d projected radius (in angular units of arcsec)
        :param kwargs_mass: mass model parameters (following lenstronomy lens model conventions)
        :param kwargs_light: deflector light parameters (following lenstronomy light model conventions)
        :param kwargs_anisotropy: anisotropy parameters, may vary according to anisotropy type chosen.
            We refer to the Anisotropy() class for details on the parameters.
        :return: line-of-sight projected velocity dispersion at projected radius R from 3d radius r
        """
        a, gamma, rho0_r0_gamma, r_ani = self._read_out_params(kwargs_mass, kwargs_light, kwargs_anisotropy)
        return self._sigma_s2(r, R, r_ani, a, gamma, rho0_r0_gamma), 1

    def sigma_r2(self, r, kwargs_mass, kwargs_light, kwargs_anisotropy):
        """
        equation (19) in Suyu+ 2010

        :param r: 3d radius
        :param kwargs_mass: mass profile keyword arguments
        :param kwargs_light: light profile keyword arguments
        :param kwargs_anisotropy: anisotropy keyword arguments
        :return: velocity dispersion in [m/s]
        """
        a, gamma, rho0_r0_gamma, r_ani = self._read_out_params(kwargs_mass, kwargs_light, kwargs_anisotropy)
        return self._sigma_r2(r, a, gamma, rho0_r0_gamma, r_ani)

    def _read_out_params(self, kwargs_mass, kwargs_light, kwargs_anisotropy):
        """
        reads the relevant parameters out of the keyword arguments and transforms them to the conventions used in this
        class

        :param kwargs_mass: mass profile keyword arguments
        :param kwargs_light: light profile keyword arguments
        :param kwargs_anisotropy: anisotropy keyword arguments
        :return: a (Rs of Hernquist profile), gamma, rho0_r0_gamma, r_ani
        """
        if 'a' not in kwargs_light:
            kwargs_light['a'] = 0.551 * kwargs_light['r_eff']
        if 'rho0_r0_gamma' not in kwargs_mass:
            kwargs_mass['rho0_r0_gamma'] = self._rho0_r0_gamma(kwargs_mass['theta_E'], kwargs_mass['gamma'])
        a = kwargs_light['a']
        gamma = kwargs_mass['gamma']
        rho0_r0_gamma = kwargs_mass['rho0_r0_gamma']
        r_ani = kwargs_anisotropy['r_ani']
        return a, gamma, rho0_r0_gamma, r_ani

    def _sigma_r2(self, r, a, gamma, rho0_r0_gamma, r_ani):
        """
        equation (19) in Suyu+ 2010
        """
        # first term
        prefac1 = 4*np.pi * const.G * a**(-gamma) * rho0_r0_gamma / (3-gamma)
        prefac2 = r * (r + a)**3/(r**2 + r_ani**2)
        # TODO check whether interpolation functions can speed this up
        hyp1 = vel_util.hyp_2F1(a=2+gamma, b=gamma, c=3+gamma, z=1./(1+r/a))
        hyp2 = vel_util.hyp_2F1(a=3, b=gamma, c=1+gamma, z=-a/r)
        fac = r_ani**2/a**2 * hyp1 / ((2+gamma) * (r/a + 1)**(2+gamma)) + hyp2 / (gamma*(r/a)**gamma)
        return prefac1 * prefac2 * fac * (const.arcsec * self._cosmo.dd * const.Mpc) ** 2

    def _sigma_r2_interp(self, r, a, gamma, rho0_r0_gamma, r_ani):
        """

        :param r:
        :param a:
        :param gamma:
        :param rho0_r0_gamma:
        :param r_ani:
        :return:
        """
        if not hasattr(self, '_interp_sigma_r2'):
            min_log = np.log10(self._min_integrate)
            max_log = np.log10(self._max_integrate)
            r_array = np.logspace(min_log, max_log, self._interp_grid_num)
            I_R_sigma2_array = []
            for r_i in r_array:
                I_R_sigma2_array.append(self._sigma_r2(r_i, a, gamma, rho0_r0_gamma, r_ani))
            self._interp_sigma_r2 = interp1d(np.log(r_array), np.array(I_R_sigma2_array), fill_value="extrapolate")
        return self._interp_sigma_r2(np.log(r))

    def grav_potential(self, r, kwargs_mass):
        """
        Gravitational potential in SI units

        :param r: radius (arc seconds)
        :param kwargs_mass:
        :return: gravitational potential
        """
        theta_E = kwargs_mass['theta_E']
        gamma = kwargs_mass['gamma']
        mass_dimless = self._spp.mass_3d_lens(r, theta_E, gamma)
        mass_dim = mass_dimless * const.arcsec ** 2 * self._cosmo.dd * self._cosmo.ds / self._cosmo.dds * const.Mpc * \
            const.c ** 2 / (4 * np.pi * const.G)
        grav_pot = -const.G * mass_dim / (r * const.arcsec * self._cosmo.dd * const.Mpc)
        return grav_pot

    def delete_cache(self):
        """
        deletes temporary cache tight to a specific model

        :return:
        """
        if hasattr(self, '_interp_sigma_r2'):
            del self._interp_sigma_r2
