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
from theano.compile import Mode
from .mode import get_mode

try:
    from theano.gpuarray.type import GpuArrayType, _name_for_ctx
    from pygpu.gpuarray import GpuArray
    pygpu_available = True
except ImportError:
    pygpu_available = False


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


def _is_numeric_value(arr, var):
    """
    Checks a variable against non-numeric types such as types, slices,
    empty arrays, and None, that need not be checked for NaN and Inf values.

    Parameters
    ----------
    arr : the data of that correspond to any Theano Variable
    var : The corresponding Theano variable

    Returns
    -------
    is_non_numeric : bool
        `True` the value is non-numeric.

    """
    if isinstance(arr, theano.gof.type._cdata_type):
        return False
    elif isinstance(arr, np.random.mtrand.RandomState):
        return False
    elif var and getattr(var.tag, 'is_rng', False):
        return False
    elif isinstance(arr, slice):
        return False
    elif arr is None:
        return False
    elif arr.size == 0:
        return False
    return True


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, var=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.
    var : The Theano symbolic variable.

    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 not _is_numeric_value(arr, var):
        return False
    elif pygpu_available and isinstance(arr, GpuArray):
        return np.isnan(f_gpua_min(arr.reshape(arr.size)))

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


def contains_inf(arr, node=None, var=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.
    var : The Theano symbolic variable.

    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 not _is_numeric_value(arr, var):
        return False
    elif pygpu_available and isinstance(arr, GpuArray):
        return (np.isinf(f_gpua_min(arr.reshape(arr.size))) or
                np.isinf(f_gpua_max(arr.reshape(arr.size))))

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


def f_compute(op):
    def result(inp):
        dtype = inp.dtype
        ctx_name = _name_for_ctx(inp.context)
        key = (dtype, ctx_name)
        f = result.cache.get(key, None)
        if f is None:
            guard_in = GpuArrayType(str(dtype), (False,), context_name=ctx_name)()
            mode = get_mode('FAST_RUN').including('gpuarray')
            f = theano.function([guard_in], op(guard_in),
                                mode=mode, profile=False)
            result.cache[key] = f
        return f(inp)
    result.cache = dict()
    return result

f_gpua_min = f_compute(T.min)
f_gpua_max = f_compute(T.max)
f_gpua_absmax = f_compute(lambda x: T.max(T.abs_(x)))


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

        def do_check_on(value, nd, var=None):
            """
            Checks `value` 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
            ----------
            value : numpy.ndarray
                The value to be checked.
            nd : theano.gof.Apply
                The Apply node being executed.
            var : theano.gof.Variable
                Not used if nd is there. Otherwise, used to print the stack
                trace for inputs of the graph.

            """
            error = False
            sio = StringIO()
            if nan_is_error:
                if contains_nan(value, nd, var):
                    print('NaN detected', file=sio)
                    error = True
            if inf_is_error:
                if contains_inf(value, nd, var):
                    print('Inf detected', file=sio)
                    error = True
            if big_is_error:
                err = False
                if not _is_numeric_value(value, var):
                    err = False
                elif pygpu_available and isinstance(value, GpuArray):
                    err = (f_gpua_absmax(value.reshape(value.size)) > 1e10)
                else:
                    err = (np.abs(value).max() > 1e10)
                if err:
                    print('Big value detected', file=sio)
                    error = True
            if error:
                if nd:
                    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 the "
                          "graph.", file=sio)
                # Add the stack trace
                if nd:
                    var = nd.outputs[0]
                print(theano.gof.utils.get_variable_trace_string(var),
                      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(node, thunk, storage_map, compute_map):
            for var in node.outputs:
                if (compute_map[var][0] and
                        getattr(var.tag, 'nan_guard_mode_check', True)):
                    do_check_on(storage_map[var][0], node)

        def nan_check_input(var, value):
            if getattr(var.tag, 'nan_guard_mode_check', True):
                do_check_on(value, None, var=var)

        wrap_linker = theano.gof.vm.VM_Linker(callback=nan_check,
                                              callback_input=nan_check_input)
        super(NanGuardMode, self).__init__(wrap_linker,
                                           optimizer=self.provided_optimizer)
