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r"""

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Interface for elements which provide a Fourier expansion.

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AUTHOR :

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    -- Martin Raum (2009 - 08 - 03) Initial version

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"""

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#===============================================================================

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# 

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# Copyright (C) 2009 Martin Raum

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# 

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# This program is free software; you can redistribute it and/or

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# modify it under the terms of the GNU General Public License

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# as published by the Free Software Foundation; either version 3

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# of the License, or (at your option) any later version.

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# 

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# This program is distributed in the hope that it will be useful, 

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# but WITHOUT ANY WARRANTY; without even the implied warranty of

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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

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# General Public License for more details.

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# 

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# You should have received a copy of the GNU General Public License

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# along with this program; if not, see <http://www.gnu.org/licenses/>.

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#

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#===============================================================================

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class FourierExpansionWrapper :

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    r"""

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    Abstract class for elements, which do not represent Fourier

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    expansions on their own, but encapsulate one.

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    SEE:

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        :class:~`fourier_expansion_framework.gradedexpansions.GradedExpansion_class`.

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    """

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    def fourier_expansion(self, cache = True) :

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        r"""

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        The Fourier expansion which is associated with ``self``.

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        INPUT:

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            - ``cache`` -- A boolean (default: ``True``); If ``True`` the return value

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                           will be cached.

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        OUTPUT:

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            A (equivariant) monoid power series.

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        NOTE:

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            The parent has to implement the function ``_fourier_expansion_of_element``.

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        TESTS::

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            sage: from psage.modform.fourier_expansion_framework.gradedexpansions import *

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            sage: from psage.modform.fourier_expansion_framework.monoidpowerseries import *

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            sage: from psage.modform.fourier_expansion_framework.monoidpowerseries.monoidpowerseries_basicmonoids import *

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            sage: emps = EquivariantMonoidPowerSeriesRing(NNMonoid(True), TrivialCharacterMonoid("1", ZZ), TrivialRepresentation("1", ZZ))

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            sage: em = ExpansionModule(Sequence([emps.one_element().truncate(3), emps.one_element(), emps.one_element()]))

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            sage: h = em([1,2,-3])

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            sage: fe = h.fourier_expansion()

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        """

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        try :

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            return self.__fourier_expansion

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        except AttributeError :

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            if cache :

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                self.__fourier_expansion = \

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                  self.parent()._fourier_expansion_of_element(self)

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                return self.__fourier_expansion

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            else :

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                return self.parent()._fourier_expansion_of_element(self)

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    def _set_fourier_expansion(self, expansion ) :

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        r"""

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        Set the cache for the Fourier expansion to an given monoid power series.

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        INPUT:

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            - ``expansion`` -- A (equivariant) monoid power series.

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        OUTPUT:

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            ``None``

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        TESTS::

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            sage: from psage.modform.fourier_expansion_framework.gradedexpansions import *

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            sage: from psage.modform.fourier_expansion_framework.monoidpowerseries import *

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            sage: from psage.modform.fourier_expansion_framework.monoidpowerseries.monoidpowerseries_basicmonoids import *

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            sage: emps = EquivariantMonoidPowerSeriesRing(NNMonoid(True), TrivialCharacterMonoid("1", ZZ), TrivialRepresentation("1", ZZ))

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            sage: em = ExpansionModule(Sequence([emps.one_element().truncate(3), emps.one_element(), emps.one_element()]))

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            sage: h = em([1,2,5])

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            sage: fe = h.fourier_expansion()

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            sage: h = em([1,2,0])

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            sage: h._set_fourier_expansion(fe)

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            sage: h.fourier_expansion() == fe

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            True

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        """

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        self.__fourier_expansion = expansion

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