import galsim
import sep
import numpy as np
from scipy.interpolate import interp1d
import pylab as pl
import os
import sys


class PSFModel(object):
    def __init__(self, sigSpin=0., psfRa=0.15):
        # TODO: what are the nesseary fields in PSFModel class?
        pass

    def PSFspin(self, psf, sigSpin, sigGauss, dx, dy):
        """
        The PSF profile at a given image position relative to the axis center

        Parameters:
        theta : spin angles in a given exposure in unit of [arcsecond]
        dx, dy: relative position to the axis center in unit of [pixels]

        Return:
        Spinned PSF: g1, g2 and axis ratio 'a/b'
        """
        a2Rad = np.pi/(60.0*60.0*180.0)

        ff = sigGauss * 0.107 * (1000.0/10.0)  # in unit of [pixels]
        rc = np.sqrt(dx*dx + dy*dy)
        cpix = rc*(sigSpin*a2Rad)

        beta = (np.arctan2(dy, dx) + np.pi/2)
        ell = cpix**2/(2.0*ff**2+cpix**2)
        # ell *= 10.0
        qr = np.sqrt((1.0+ell)/(1.0-ell))

        # psfShape = galsim.Shear(e=ell, beta=beta)
        # g1, g2 = psfShape.g1, psfShape.g2
        # qr = np.sqrt((1.0+ell)/(1.0-ell))

        # return ell, beta, qr
        PSFshear = galsim.Shear(e=ell, beta=beta*galsim.radians)
        return psf.shear(PSFshear), PSFshear