# Copyright (C) 2012  Alex Nitz
#
#
# This program is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the
# Free Software Foundation; either version 3 of the License, or (at your
# option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
# Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.


#
# =============================================================================
#
#                                   Preamble
#
# =============================================================================
#
"""This module provides utilities for calculating detector responses.
"""
import lalsimulation
import numpy as np
import lal
from math import cos, sin
from pycbc.types import TimeSeries


class Detector(object):
    """A gravitaional wave detector
    """
    def __init__(self, detector_name):
        self.name = str(detector_name)
        self.frDetector =  lalsimulation.DetectorPrefixToLALDetector(self.name)
        self.response = self.frDetector.response
        self.location = self.frDetector.location

    def light_travel_time_to_detector(self, det):
        """ Return the light travel time from this detector
        
        Parameters
        ----------
        detector: Detector
            The other detector to determine the light travel time to.
        
        Returns
        -------
        time: float
            The light travel time in seconds
        """
        return lal.LightTravelTime(self.frDetector, det.frDetector) * 1e-9

    def antenna_pattern(self, right_ascension, declination, polarization, t_gps):
        """Return the detector response.
        """
        gmst = lal.GreenwichMeanSiderealTime(t_gps)
        return tuple(lal.ComputeDetAMResponse(self.response, 
                     right_ascension, declination, polarization, gmst))
                     
    def time_delay_from_earth_center(self, right_ascension, declination, t_gps):
        """Return the time delay from the earth center
        """
        return lal.TimeDelayFromEarthCenter(self.location, right_ascension, declination, t_gps) 

    def project_wave(self, hp, hc, longitude, latitude, polarization):
        """Return the strain of a wave with given amplitudes and angles as
        measured by the detector.
        """
        h_lal = lalsimulation.SimDetectorStrainREAL8TimeSeries(
                hp.astype(np.float64).lal(), hc.astype(np.float64).lal(),
                longitude, latitude, polarization, self.frDetector)
        return TimeSeries(
                h_lal.data.data, delta_t=h_lal.deltaT, epoch=h_lal.epoch,
                dtype=np.float64, copy=False)


def overhead_antenna_pattern(right_ascension, declination, polarization):
    """Return the detector response where (0, 0) indicates an overhead source
    """
    f_plus = - (1.0/2.0) * (1.0 + cos(declination)*cos(declination)) * cos (2.0 * right_ascension) * cos (2.0 * polarization) - cos(declination) * sin(2.0*right_ascension) * sin (2.0 * polarization)
    f_cross=  (1.0/2.0) * (1.0 + cos(declination)*cos(declination)) * cos (2.0 * right_ascension) * sin (2.0* polarization) - cos (declination) * sin(2.0*right_ascension) * cos (2.0 * polarization)
    return f_plus, f_cross