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# Source code for astroplan.periodic

    # Licensed under a 3-clause BSD style license - see LICENSE.rst
    from __future__ import (absolute_import, division, print_function,
                            unicode_literals)
    import numpy as np
    import astropy.units as u
    from astropy.time import Time

    __all__ = ['PeriodicEvent', 'EclipsingSystem']

    class PeriodicEvent(object):
        """
        A periodic event defined by an epoch and period.
        """
        @u.quantity_input(period=u.day, duration=u.day)
        def __init__(self, epoch, period, duration=None, name=None):
            """

            Parameters
            ----------
            epoch : `~astropy.time.Time`
                Time of event
            period : `~astropy.units.Quantity`
                Period of event
            duration : `~astropy.units.Quantity` (optional)
                Duration of event
            name : str (optional)
                Name of target/event
            """
            self.epoch = epoch
            self.period = period
            self.name = name
            self.duration = duration

        def phase(self, time):
            """
            Phase of periodic event, on interval [0, 1). For example, the phase
            could be an orbital phase for an eclipsing binary system.

            Parameters
            ----------
            time : `~astropy.time.Time`
                Evaluate the phase at this time or times

            Returns
            -------
            phase_array : `~numpy.ndarray`
                Phase at each ``time``, on range [0, 1)
            """
            return ((time - self.epoch).to(u.day).value %
                    self.period.to(u.day).value) / self.period.to(u.day).value

    class EclipsingSystem(PeriodicEvent):
        """
        Define parameters for an eclipsing system; useful for an eclipsing binary or
        transiting exoplanet.

        .. warning::
            There are currently two major caveats in the implementation of
            ``EclipsingSystem``. The secondary eclipse time approximation is
            only accurate when the orbital eccentricity is small, and the eclipse
            times are computed without any barycentric corrections. The current
            implementation should only be used forapproximate mid-eclipse times for
            low eccentricity orbits, with event durations longer than the
            barycentric correction error (<=16 minutes).
        """
        @u.quantity_input(period=u.day, duration=u.day)
        def __init__(self, primary_eclipse_time, orbital_period, duration=None,
                     name=None, eccentricity=None, argument_of_periapsis=None):
            """
            Parameters
            ----------
            primary_eclipse_time : `~astropy.time.Time`
                Time of primary eclipse
            orbital_period : `~astropy.units.Quantity`
                Orbital period of eclipsing system
            duration : `~astropy.units.Quantity` (optional)
                Duration of eclipse
            name : str (optional)
                Name of target/event
            eccentricity : float (optional)
                Orbital eccentricity. Default is `None`, which assumes circular
                orbit (e=0).
            argument_of_periapsis : float (optional)
                Argument of periapsis for the eclipsing system, in radians.
                Default is `None`, which assumes pi/2.
            """
            self.epoch = primary_eclipse_time
            self.period = orbital_period
            self.name = name
            self.duration = duration

            if eccentricity is None:
                eccentricity = 0
            self.eccentricity = eccentricity

            if argument_of_periapsis is None:
                argument_of_periapsis = np.pi/2
            self.argument_of_periapsis = argument_of_periapsis

        def in_primary_eclipse(self, time):
            """
            Returns `True` when ``time`` is during a primary eclipse.

            .. warning::
                Barycentric offsets are ignored in the current implementation.

            Parameters
            ----------
            time : `~astropy.time.Time`
                Time to evaluate

            Returns
            -------
            in_eclipse : `~numpy.ndarray` or bool
                `True` if ``time`` is during primary eclipse
            """
            phases = self.phase(time)
            return ((phases < float(self.duration/self.period)/2) |
                    (phases > 1 - float(self.duration/self.period)/2))

        def in_secondary_eclipse(self, time):
            r"""
            Returns `True` when ``time`` is during a secondary eclipse

            If the eccentricity of the eclipsing system is non-zero, then we compute
            the secondary eclipse time approximated to first order in eccentricity,
            as described in Winn (2010) Equation 33 [1]_:

            The time between the primary eclipse and secondary eclipse :math:`\delta t_c`
            is given by :math:`\delta t_c \approx 0.5 \left (\frac{4}{\pi} e \cos{\omega \right)`,
            where :math:`e` is the orbital eccentricity and :math:`\omega` is the
            angle of periapsis.

            .. warning::
                This approximation for the secondary eclipse time is only accurate
                when the orbital eccentricity is small; and barycentric offsets
                are ignored in the current implementation.

            Parameters
            ----------
            time : `~astropy.time.Time`
                Time to evaluate

            Returns
            -------
            in_eclipse : `~numpy.ndarray` or bool
                `True` if ``time`` is during secondary eclipse

            References
            ----------
            .. [1] Winn (2010) https://arxiv.org/abs/1001.2010
            """
            if self.eccentricity < 1e-5:
                secondary_eclipse_phase = 0.5
            else:
                secondary_eclipse_phase = 0.5 * (1 + 4/np.pi * self.eccentricity *
                                                 np.cos(self.argument_of_periapsis))
            phases = self.phase(time)
            return ((phases < secondary_eclipse_phase + float(self.duration/self.period)/2) &
                    (phases > secondary_eclipse_phase - float(self.duration/self.period)/2))

        def out_of_eclipse(self, time):
            """
            Returns `True` when ``time`` is not during primary or secondary eclipse.

            .. warning::
                Barycentric offsets are ignored in the current implementation.

            Parameters
            ----------
            time : `~astropy.time.Time`
                Time to evaluate

            Returns
            -------
            in_eclipse : `~numpy.ndarray` or bool
                `True` if ``time`` is not during primary or secondary eclipse
            """
            return np.logical_not(np.logical_or(self.in_primary_eclipse(time),
                                                self.in_secondary_eclipse(time)))

        def next_primary_eclipse_time(self, time, n_eclipses=1):
            """
            Time of the next primary eclipse after ``time``.

            .. warning::
                Barycentric offsets are ignored in the current implementation.

            Parameters
            ----------
            time : `~astropy.time.Time`
                Find the next primary eclipse after ``time``
            n_eclipses : int (optional)
                Return the times of eclipse for the next ``n_eclipses`` after
                ``time``. Default is 1.

            Returns
            -------
            primary_eclipses : `~astropy.time.Time`
                Times of the next ``n_eclipses`` primary eclipses after ``time``
            """
            eclipse_times = ((1-self.phase(time)) * self.period + time +
                             np.arange(n_eclipses) * self.period)
            return eclipse_times

        def next_secondary_eclipse_time(self, time, n_eclipses=1):
            """
            Time of the next secondary eclipse after ``time``.

            .. warning::
                Barycentric offsets are ignored in the current implementation.

            Parameters
            ----------
            time : `~astropy.time.Time`
                Find the next secondary eclipse after ``time``
            n_eclipses : int (optional)
                Return the times of eclipse for the next ``n_eclipses`` after
                ``time``. Default is 1.

            Returns
            -------
            secondary_eclipses : `~astropy.time.Time`
                Times of the next ``n_eclipses`` secondary eclipses after ``time``
            """
            phase = self.phase(time)
            if phase >= 0.5:
                next_eclipse_phase = 1.5
            else:
                next_eclipse_phase = 0.5
            eclipse_times = ((next_eclipse_phase - phase) * self.period + time +
                             np.arange(n_eclipses) * self.period)
            return eclipse_times

        def next_primary_ingress_egress_time(self, time, n_eclipses=1):
            """
            Calculate the times of ingress and egress for the next ``n_eclipses``
            primary eclipses after ``time``

            .. warning::
                Barycentric offsets are ignored in the current implementation.

            Parameters
            ----------
            time : `~astropy.time.Time`
                Find the next primary ingress and egress after ``time``
            n_eclipses : int (optional)
                Return the times of eclipse for the next ``n_eclipses`` after
                ``time``. Default is 1.

            Returns
            -------
            primary_eclipses : `~astropy.time.Time` of shape (``n_eclipses``, 2)
                Times of ingress and egress for the next ``n_eclipses`` primary
                eclipses after ``time``
            """
            next_mid_eclipses = self.next_primary_eclipse_time(time, n_eclipses=n_eclipses)
            next_ingresses = next_mid_eclipses - self.duration/2
            next_egresses = next_mid_eclipses + self.duration/2

            ing_egr = np.vstack([next_ingresses.utc.jd, next_egresses.utc.jd]).T

            return Time(ing_egr, format='jd', scale='utc')

        def next_secondary_ingress_egress_time(self, time, n_eclipses=1):
            """
            Calculate the times of ingress and egress for the next ``n_eclipses``
            secondary eclipses after ``time``

            .. warning::
                Barycentric offsets are ignored in the current implementation.

            Parameters
            ----------
            time : `~astropy.time.Time`
                Find the next secondary ingress and egress after ``time``
            n_eclipses : int (optional)
                Return the times of eclipse for the next ``n_eclipses`` after
                ``time``. Default is 1.

            Returns
            -------
            secondary_eclipses : `~astropy.time.Time` of shape (``n_eclipses``, 2)
                Times of ingress and egress for the next ``n_eclipses`` secondary
                eclipses after ``time``.
            """
            next_mid_eclipses = self.next_secondary_eclipse_time(time, n_eclipses=n_eclipses)
            next_ingresses = next_mid_eclipses - self.duration/2
            next_egresses = next_mid_eclipses + self.duration/2

            ing_egr = np.vstack([next_ingresses.utc.jd, next_egresses.utc.jd]).T

            return Time(ing_egr, format='jd', scale='utc')