"""This module provides a convenient constructor for the `Scan` `Op`."""

__docformat__ = "restructedtext en"
__authors__ = "Razvan Pascanu " "Frederic Bastien " "James Bergstra " "Pascal Lamblin "
__copyright__ = "(c) 2010, Universite de Montreal"
__contact__ = "Razvan Pascanu <r.pascanu@gmail>"


import logging

from theano.scan import scan


_logger = logging.getLogger("theano.scan.views")


def map(
    fn,
    sequences,
    non_sequences=None,
    truncate_gradient=-1,
    go_backwards=False,
    mode=None,
    name=None,
):
    """Construct a `Scan` `Op` that functions like `map`.

    Parameters
    ----------
    fn
        The function that ``map`` applies at each iteration step
        (see ``scan`` for more info).
    sequences
        List of sequences over which ``map`` iterates
        (see ``scan`` for more info).
    non_sequences
        List of arguments passed to ``fn``. ``map`` will not iterate over
        these arguments (see ``scan`` for more info).
    truncate_gradient
        See ``scan``.
    go_backwards : bool
        Decides the direction of iteration. True means that sequences are parsed
        from the end towards the beginning, while False is the other way around.
    mode
        See ``scan``.
    name
        See ``scan``.

    """
    return scan(
        fn=fn,
        sequences=sequences,
        outputs_info=[],
        non_sequences=non_sequences,
        truncate_gradient=truncate_gradient,
        go_backwards=go_backwards,
        mode=mode,
        name=name,
    )


def reduce(
    fn,
    sequences,
    outputs_info,
    non_sequences=None,
    go_backwards=False,
    mode=None,
    name=None,
):
    """Construct a `Scan` `Op` that functions like `reduce`.

    Parameters
    ----------
    fn
        The function that ``reduce`` applies at each iteration step
        (see ``scan``  for more info).
    sequences
        List of sequences over which ``reduce`` iterates
        (see ``scan`` for more info).
    outputs_info
        List of dictionaries describing the outputs of
        reduce (see ``scan`` for more info).
    non_sequences
        List of arguments passed to ``fn``. ``reduce`` will
                          not iterate over these arguments (see ``scan`` for
                          more info).
    go_backwards : bool
        Decides the direction of iteration. True means that sequences are parsed
        from the end towards the beginning, while False is the other way around.
    mode
        See ``scan``.
    name
        See ``scan``.

    """
    rval = scan(
        fn=fn,
        sequences=sequences,
        outputs_info=outputs_info,
        non_sequences=non_sequences,
        go_backwards=go_backwards,
        truncate_gradient=-1,
        mode=mode,
        name=name,
    )
    if isinstance(rval[0], (list, tuple)):
        return [x[-1] for x in rval[0]], rval[1]
    else:
        return rval[0][-1], rval[1]


def foldl(fn, sequences, outputs_info, non_sequences=None, mode=None, name=None):
    """Construct a `Scan` `Op` that functions like Haskell's `foldl`.

    Parameters
    ----------
    fn
        The function that ``foldl`` applies at each iteration step
        (see ``scan`` for more info).
    sequences
        List of sequences over which ``foldl`` iterates
        (see ``scan`` for more info).
    outputs_info
        List of dictionaries describing the outputs of reduce
        (see ``scan`` for more info).
    non_sequences
        List of arguments passed to `fn`. ``foldl`` will not iterate over
        these arguments (see ``scan`` for more info).
    mode
        See ``scan``.
    name
        See ``scan``.

    """
    return reduce(
        fn=fn,
        sequences=sequences,
        outputs_info=outputs_info,
        non_sequences=non_sequences,
        go_backwards=False,
        mode=mode,
        name=name,
    )


def foldr(fn, sequences, outputs_info, non_sequences=None, mode=None, name=None):
    """Construct a `Scan` `Op` that functions like Haskell's `foldr`.

    Parameters
    ----------
    fn
        The function that ``foldr`` applies at each iteration step
        (see ``scan`` for more info).
    sequences
        List of sequences over which ``foldr`` iterates
        (see ``scan`` for more info).
    outputs_info
        List of dictionaries describing the outputs of reduce
        (see ``scan`` for more info).
    non_sequences
        List of arguments passed to `fn`. ``foldr`` will not iterate over these
        arguments (see ``scan`` for more info).
    mode
        See ``scan``.
    name
        See ``scan``.

    """
    return reduce(
        fn=fn,
        sequences=sequences,
        outputs_info=outputs_info,
        non_sequences=non_sequences,
        go_backwards=True,
        mode=mode,
        name=name,
    )
