from __future__ import absolute_import, print_function, division
import collections
import logging

from six.moves import StringIO
import numpy as np

import theano
from theano.configparser import config
import theano.tensor as T
import theano.sandbox.cuda as cuda
from theano.compile import Mode

logger = logging.getLogger("theano.compile.nanguardmode")


def flatten(l):
    """
    Turns a nested graph of lists/tuples/other objects into a list of objects.

    Parameters
    ----------
    l : list/tuple/other objects
        Might be nested.

    Returns
    -------
    object
        A flattened list of objects.

    """
    if isinstance(l, (list, tuple, collections.ValuesView)):
        rval = []
        for elem in l:
            if isinstance(elem, (list, tuple)):
                rval.extend(flatten(elem))
            else:
                rval.append(elem)
    else:
        return [l]
    return rval


def contains_nan(arr, node=None):
    """
    Test whether a numpy.ndarray contains any `np.nan` values.

    Parameters
    ----------
    arr : np.ndarray or output of any Theano op
    node : None or an Apply instance.
        If arr is the output of a Theano op, the node associated to it.

    Returns
    -------
    contains_nan : bool
        `True` if the array contains any `np.nan` values, `False` otherwise.

    Notes
    -----
    Tests for the presence of `np.nan`'s using `np.isnan(np.min(ndarray))`.
    This approach is faster and more memory efficient than the obvious
    alternative, calling `np.any(np.isnan(ndarray))`, which requires the
    construction of a boolean array with the same shape as the input array.

    """
    if isinstance(arr, theano.gof.type.CDataType._cdata_type):
        return False
    elif isinstance(arr, np.random.mtrand.RandomState):
        return False
    elif isinstance(arr, slice):
        return False
    elif arr.size == 0:
        return False
    elif cuda.cuda_available and isinstance(arr, cuda.CudaNdarray):
        if (hasattr(theano.sandbox, 'rng_mrg') and
            isinstance(
                node.op,
                # It store ints in float container
                theano.sandbox.rng_mrg.GPU_mrg_uniform)):
            return False
        else:
            compile_gpu_func(True, False, False)
            return np.isnan(f_gpumin(arr.reshape(arr.size)))

    return np.isnan(np.min(arr))


def contains_inf(arr, node=None):
    """
    Test whether a numpy.ndarray contains any `np.inf` values.

    Parameters
    ----------
    arr : np.ndarray or output of any Theano op
    node : None or an Apply instance.
        If the output of a Theano op, the node associated to it.

    Returns
    -------
    contains_inf : bool
        `True` if the array contains any `np.inf` values, `False` otherwise.

    Notes
    -----
    Tests for the presence of `np.inf`'s by determining whether the
    values returned by `np.nanmin(arr)` and `np.nanmax(arr)` are finite.
    This approach is more memory efficient than the obvious alternative,
    calling `np.any(np.isinf(ndarray))`, which requires the construction of a
    boolean array with the same shape as the input array.

    """
    if isinstance(arr, theano.gof.type.CDataType._cdata_type):
        return False
    elif isinstance(arr, np.random.mtrand.RandomState):
        return False
    elif isinstance(arr, slice):
        return False
    elif arr.size == 0:
        return False
    elif cuda.cuda_available and isinstance(arr, cuda.CudaNdarray):
        if (hasattr(theano.sandbox, 'rng_mrg') and
            isinstance(
                node.op,
                # It store ints in float container
                theano.sandbox.rng_mrg.GPU_mrg_uniform)):
            return False
        else:
            compile_gpu_func(False, True, False)
            return (np.isinf(f_gpumin(arr.reshape(arr.size))) or
                    np.isinf(f_gpumax(arr.reshape(arr.size))))

    return np.isinf(np.nanmax(arr)) or np.isinf(np.nanmin(arr))

f_gpumin = None
f_gpumax = None
f_gpuabsmax = None


def compile_gpu_func(nan_is_error, inf_is_error, big_is_error):
    """ compile utility function used by contains_nan and contains_inf
    """
    global f_gpumin, f_gpumax, f_gpuabsmax
    if not cuda.cuda_available:
        return
    guard_input = cuda.fvector('nan_guard')
    cuda_compile_failed = False
    if (nan_is_error or inf_is_error) and f_gpumin is None:
        try:
            f_gpumin = theano.function(
                [guard_input], T.min(guard_input),
                mode='FAST_RUN'
            )
        except RuntimeError:
            # This can happen if cuda is available, but the
            # device is in exclusive mode and used by another
            # process.
            cuda_compile_failed = True
    if inf_is_error and not cuda_compile_failed and f_gpumax is None:
        try:
            f_gpumax = theano.function(
                [guard_input], T.max(guard_input),
                mode='FAST_RUN'
            )
        except RuntimeError:
            # This can happen if cuda is available, but the
            # device is in exclusive mode and used by another
            # process.
            cuda_compile_failed = True
    if big_is_error and not cuda_compile_failed and f_gpuabsmax is None:
        try:
            f_gpuabsmax = theano.function(
                [guard_input], T.max(T.abs_(guard_input)),
                mode='FAST_RUN'
                )
        except RuntimeError:
            # This can happen if cuda is available, but the
            # device is in exclusive mode and used by another
            # process.
            cuda_compile_failed = True


class NanGuardMode(Mode):
    """
    A Theano compilation Mode that makes the compiled function automatically
    detect NaNs and Infs and detect an error if they occur.

    Parameters
    ----------
    nan_is_error : bool
        If True, raise an error anytime a NaN is encountered.
    inf_is_error : bool
        If True, raise an error anytime an Inf is encountered.  Note that some
        pylearn2 modules currently use np.inf as a default value (e.g.
        mlp.max_pool) and these will cause an error if inf_is_error is True.
    big_is_error : bool
        If True, raise an error when a value greater than 1e10 is encountered.

    Note
    ----
        We ignore the linker parameter
    """
    # We currently loose the 3 first params frequently, when calling
    # mode.including() and variant.
    def __init__(self, nan_is_error=None, inf_is_error=None, big_is_error=None,
                 optimizer='default', linker=None):
        self.provided_optimizer = optimizer
        if nan_is_error is None:
            nan_is_error = config.NanGuardMode.nan_is_error
        if inf_is_error is None:
            inf_is_error = config.NanGuardMode.inf_is_error
        if big_is_error is None:
            big_is_error = config.NanGuardMode.big_is_error

        assert nan_is_error or inf_is_error or big_is_error
        compile_gpu_func(nan_is_error, inf_is_error, big_is_error)

        def do_check_on(var, nd, f, is_input):
            """
            Checks `var` for NaNs / Infs. If detected, raises an exception
            and / or prints information about `nd`, `f`, and `is_input` to
            help the user determine the cause of the invalid values.

            Parameters
            ----------
            var : numpy.ndarray
                The value to be checked.
            nd : theano.gof.Apply
                The Apply node being executed.
            f : callable
                The thunk for the apply node.
            is_input : bool
                If True, `var` is an input to `nd`.
                If False, it is an output.

            """
            error = False
            sio = StringIO()
            if nan_is_error:
                if contains_nan(var, nd):
                    print('NaN detected', file=sio)
                    error = True
            if inf_is_error:
                if contains_inf(var, nd):
                    print('Inf detected', file=sio)
                    error = True
            if big_is_error:
                err = False
                if isinstance(var, theano.gof.type.CDataType._cdata_type):
                    err = False
                elif isinstance(var, np.random.mtrand.RandomState):
                    err = False
                elif isinstance(var, slice):
                    err = False
                elif var.size == 0:
                    err = False
                elif cuda.cuda_available and isinstance(var, cuda.CudaNdarray):
                    err = (f_gpuabsmax(var.reshape(var.size)) > 1e10)
                else:
                    err = (np.abs(var).max() > 1e10)
                if err:
                    print('Big value detected', file=sio)
                    error = True
            if error:
                if not is_input:
                    print("NanGuardMode found an error in the"
                          " output of a node in this variable:", file=sio)
                    print(theano.printing.debugprint(nd, file='str'), file=sio)
                else:
                    print("NanGuardMode found an error in an"
                          " input of this node.", file=sio)
                    print('Node:', file=sio)
                    print(nd, file=sio)
                    print("The input variable that cause problem:", file=sio)
                    print(theano.printing.debugprint(nd, file='str'), file=sio)
                msg = sio.getvalue()
                if config.NanGuardMode.action == 'raise':
                    raise AssertionError(msg)
                elif config.NanGuardMode.action == 'pdb':
                    print(msg)
                    import pdb
                    pdb.set_trace()
                elif config.NanGuardMode.action == 'warn':
                    logger.error(msg)

        def nan_check(i, node, fn):
            """
            Runs `fn` while checking its inputs and outputs for NaNs / Infs.

            Parameters
            ----------
            i :
                Currently ignored.
                TODO: determine why it is here or remove).
            node : theano.gof.Apply
                The Apply node currently being executed.
            fn : callable
                The thunk to execute for this Apply node.

            """
            inputs = fn.inputs
            for x, var in zip(inputs, node.inputs):
                # If the input is the result of computation, then we
                # don't need to check it. It is already done after the
                # computation.
                if (var.owner is None and
                        getattr(var.tag, 'nan_guard_mode_check', True)):
                    do_check_on(x[0], node, fn, True)
            fn()
            outputs = fn.outputs
            for x, var in zip(outputs, node.outputs):
                if getattr(var.tag, 'nan_guard_mode_check', True):
                    do_check_on(x[0], node, fn, False)

        wrap_linker = theano.gof.WrapLinker([theano.gof.OpWiseCLinker()],
                                            nan_check)
        super(NanGuardMode, self).__init__(wrap_linker,
                                           optimizer=self.provided_optimizer)
