# 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, see <http://www.gnu.org/licenses/>.
#
# Copyright(C) 2013-2018 Max-Planck-Society
#
# NIFTy is being developed at the Max-Planck-Institut fuer Astrophysik
# and financially supported by the Studienstiftung des deutschen Volkes.

from __future__ import absolute_import, division, print_function

from .. import dobj
from ..compat import *
from ..domain_tuple import DomainTuple
from ..field import Field
from ..utilities import hartley, infer_space
from .linear_operator import LinearOperator


class QHTOperator(LinearOperator):
    """
    Does a Hartley transform on LogRGSpace

    This operator takes a field on a LogRGSpace and transforms it
    according to the Hartley transform. The zero modes are not transformed
    because they are infinitely far away.

    Parameters
    ----------
    domain : domain, tuple of domains or DomainTuple
        The full input domain
    space : int
        The index of the domain on which the operator acts.
        domain[space] must be a harmonic LogRGSpace.
    target : LogRGSpace
        The target codomain of domain[space]
        Must be a nonharmonic LogRGSpace.
    """
    def __init__(self, domain, target, space=0):
        self._domain = DomainTuple.make(domain)
        self._space = infer_space(self._domain, space)

        from ..domains.log_rg_space import LogRGSpace
        if not isinstance(self._domain[self._space], LogRGSpace):
            raise ValueError("Domain[space] has to be a LogRGSpace!")
        if not isinstance(target, LogRGSpace):
            raise ValueError("Target has to be a LogRGSpace!")

        if not self._domain[self._space].harmonic:
            raise TypeError(
                "QHTOperator only works on a harmonic space")
        if target.harmonic:
            raise TypeError("Target is not a codomain of domain")

        self._target = [dom for dom in self._domain]
        self._target[self._space] = target
        self._target = DomainTuple.make(self._target)

    @property
    def domain(self):
        return self._domain

    @property
    def target(self):
        return self._target

    def apply(self, x, mode):
        self._check_input(x, mode)
        dom = self._domain[self._space]
        x = x.val * dom.scalar_dvol()
        n = self._domain.axes[self._space]
        rng = n if mode == self.TIMES else reversed(n)
        ax = dobj.distaxis(x)
        globshape = x.shape
        for i in rng:
            sl = (slice(None),)*i + (slice(1, None),)
            if i == ax:
                x = dobj.redistribute(x, nodist=(ax,))
            tmp = dobj.local_data(x)
            tmp[sl] = hartley(tmp[sl], axes=(i,))
            if i == ax:
                x = dobj.redistribute(x, dist=ax)
        return Field(self._tgt(mode), val=x)

    @property
    def capability(self):
        return self.TIMES | self.ADJOINT_TIMES