"""Utilities for testing nilearn.
"""
# Author: Alexandre Abrahame, Philippe Gervais
# License: simplified BSD
import contextlib
import functools
import inspect
import os
import re
import sys
import tempfile
import warnings
import copy

import numpy as np
import scipy.signal
from sklearn.utils import check_random_state
import scipy.linalg
import nibabel

from .. import datasets
from .. import masking
from . import logger
from .compat import _basestring, _urllib


try:
    from nose.tools import assert_raises_regex
except ImportError:
    # For Py 2.7
    try:
        from nose.tools import assert_raises_regexp as assert_raises_regex
    except ImportError:
        # for Py 2.6
        def assert_raises_regex(expected_exception, expected_regexp,
                                callable_obj=None, *args, **kwargs):
            """Helper function to check for message patterns in exceptions"""

            not_raised = False
            try:
                callable_obj(*args, **kwargs)
                not_raised = True
            except Exception as e:
                error_message = str(e)
                if not re.compile(expected_regexp).search(error_message):
                    raise AssertionError("Error message should match pattern "
                                         "%r. %r does not." %
                                         (expected_regexp, error_message))
            if not_raised:
                raise AssertionError("Should have raised %r" %
                                     expected_exception(expected_regexp))

try:
    from sklearn.utils.testing import assert_warns
except ImportError:
    # sklearn.utils.testing.assert_warns new in scikit-learn 0.14
    def assert_warns(warning_class, func, *args, **kw):
        with warnings.catch_warnings(record=True):
            warnings.simplefilter("ignore", warning_class)
            output = func(*args, **kw)
        return output


class MockRequest(object):
    def __init__(self, url):
        self.url = url

    def add_header(*args):
        pass


class MockOpener(object):
    def __init__(self):
        pass

    def open(self, request):
        return request.url


@contextlib.contextmanager
def write_tmp_imgs(*imgs, **kwargs):
    """Context manager for writing Nifti images.

    Write nifti images in a temporary location, and remove them at the end of
    the block.

    Parameters
    ==========
    imgs: Nifti1Image
        Several Nifti images. Every format understood by nibabel.save is
        accepted.

    create_files: bool
        if True, imgs are written on disk and filenames are returned. If
        False, nothing is written, and imgs is returned as output. This is
        useful to test the two cases (filename / Nifti1Image) in the same
        loop.

    Returns
    =======
    filenames: string or list of
        filename(s) where input images have been written. If a single image
        has been given as input, a single string is returned. Otherwise, a
        list of string is returned.
    """
    valid_keys = set(("create_files",))
    input_keys = set(kwargs.keys())
    invalid_keys = input_keys - valid_keys
    if len(invalid_keys) > 0:
        raise TypeError("%s: unexpected keyword argument(s): %s" %
                        (sys._getframe().f_code.co_name,
                         " ".join(invalid_keys)))
    create_files = kwargs.get("create_files", True)

    if create_files:
        filenames = []
        with warnings.catch_warnings():
            warnings.simplefilter("ignore", RuntimeWarning)
            for img in imgs:
                _, filename = tempfile.mkstemp(prefix="nilearn_",
                                               suffix=".nii",
                                               dir=None)
                filenames.append(filename)
                img.to_filename(filename)

        if len(imgs) == 1:
            yield filenames[0]
        else:
            yield filenames

        for filename in filenames:
            os.remove(filename)
    else:  # No-op
        if len(imgs) == 1:
            yield imgs[0]
        else:
            yield imgs


class mock_request(object):
    def __init__(self):
        """Object that mocks the urllib (future) module to store downloaded filenames.

        `urls` is the list of the files whose download has been
        requested.
        """
        self.urls = set()

    def reset(self):
        self.urls = set()

    def Request(self, url):
        self.urls.add(url)
        return MockRequest(url)

    def build_opener(self, *args, **kwargs):
        return MockOpener()


def wrap_chunk_read_(_chunk_read_):
    def mock_chunk_read_(response, local_file, initial_size=0, chunk_size=8192,
                         report_hook=None, verbose=0):
        if not isinstance(response, _basestring):
            return _chunk_read_(response, local_file,
                                initial_size=initial_size,
                                chunk_size=chunk_size,
                                report_hook=report_hook, verbose=verbose)
        return response
    return mock_chunk_read_


def mock_chunk_read_raise_error_(response, local_file, initial_size=0,
                                 chunk_size=8192, report_hook=None,
                                 verbose=0):
    raise _urllib.errors.HTTPError("url", 418, "I'm a teapot", None, None)


class FetchFilesMock (object):
    _mock_fetch_files = functools.partial(datasets._fetch_files, mock=True)

    def __init__(self):
        """Create a mock that can fill a CSV file if needed
        """
        self.csv_files = {}

    def add_csv(self, filename, content):
        self.csv_files[filename] = content

    def __call__(self, *args, **kwargs):
        """Load requested dataset, downloading it if needed or requested.

        For test purpose, instead of actually fetching the dataset, this
        function creates empty files and return their paths.
        """
        filenames = self._mock_fetch_files(*args, **kwargs)
        # Fill CSV files with given content if needed
        for fname in filenames:
            basename = os.path.basename(fname)
            if basename in self.csv_files:
                array = self.csv_files[basename]

                # np.savetxt does not have a header argument for numpy 1.6
                # np.savetxt(fname, array, delimiter=',', fmt="%s",
                #            header=','.join(array.dtype.names))
                # We need to add the header ourselves
                with open(fname, 'wb') as f:
                    header = '# {0}\n'.format(','.join(array.dtype.names))
                    f.write(header.encode())
                    np.savetxt(f, array, delimiter=',', fmt='%s')

        return filenames


def generate_timeseries(n_instants, n_features,
                        rand_gen=None):
    """Generate some random timeseries. """
    if rand_gen is None:
        rand_gen = np.random.RandomState(0)
    # TODO: add an "order" keyword
    return rand_gen.randn(n_instants, n_features)


def generate_regions_ts(n_features, n_regions,
                        overlap=0,
                        rand_gen=None,
                        window="boxcar"):
    """Generate some regions as timeseries.

    Parameters
    ==========
    overlap: int
        Number of overlapping voxels between two regions (more or less)
    window: str
        Name of a window in scipy.signal. e.g. "hamming".

    Returns
    =======
    regions: numpy.ndarray
        regions, nepresented as signals.
        shape (n_features, n_regions)
    """

    if rand_gen is None:
        rand_gen = np.random.RandomState(0)
    if window is None:
        window = "boxcar"

    assert(n_features > n_regions)

    # Compute region boundaries indices.
    # Start at 1 to avoid getting an empty region
    boundaries = np.zeros(n_regions + 1)
    boundaries[-1] = n_features
    boundaries[1:-1] = rand_gen.permutation(np.arange(1, n_features)
                                            )[:n_regions - 1]
    boundaries.sort()

    regions = np.zeros((n_regions, n_features), order="C")
    overlap_end = int((overlap + 1) / 2.)
    overlap_start = int(overlap / 2.)
    for n in range(len(boundaries) - 1):
        start = int(max(0, boundaries[n] - overlap_start))
        end = int(min(n_features, boundaries[n + 1] + overlap_end))
        win = scipy.signal.get_window(window, end - start)
        win /= win.mean()  # unity mean
        regions[n, start:end] = win

    return regions


def generate_maps(shape, n_regions, overlap=0, border=1,
                  window="boxcar", rand_gen=None, affine=np.eye(4)):
    """Generate a 4D volume containing several maps.
    Parameters
    ==========
    n_regions: int
        number of regions to generate

    overlap: int
        approximate number of voxels common to two neighboring regions

    window: str
        name of a window in scipy.signal. Used to get non-uniform regions.

    border: int
        number of background voxels on each side of the 3D volumes.

    Returns
    =======
    maps: nibabel.Nifti1Image
        4D array, containing maps.
    """

    mask = np.zeros(shape, dtype=np.int8)
    mask[border:-border, border:-border, border:-border] = 1
    ts = generate_regions_ts(mask.sum(), n_regions, overlap=overlap,
                             rand_gen=rand_gen, window=window)
    mask_img = nibabel.Nifti1Image(mask, affine)
    return masking.unmask(ts, mask_img), mask_img


def generate_labeled_regions(shape, n_regions, rand_gen=None, labels=None,
                             affine=np.eye(4), dtype=np.int):
    """Generate a 3D volume with labeled regions.

    Parameters
    ==========
    shape: tuple
        shape of returned array

    n_regions: int
        number of regions to generate. By default (if "labels" is None),
        add a background with value zero.

    labels: iterable
        labels to use for each zone. If provided, n_regions is unused.

    rand_gen: numpy.random.RandomState
        random generator to use for generation.

    affine: numpy.ndarray
        affine of returned image

    Returns
    =======
    regions: nibabel.Nifti1Image
        data has shape "shape", containing region labels.
    """
    n_voxels = shape[0] * shape[1] * shape[2]
    if labels is None:
        labels = range(0, n_regions + 1)
        n_regions += 1
    else:
        n_regions = len(labels)

    regions = generate_regions_ts(n_voxels, n_regions, rand_gen=rand_gen)
    # replace weights with labels
    for n, row in zip(labels, regions):
        row[row > 0] = n
    data = np.zeros(shape, dtype=dtype)
    data[np.ones(shape, dtype=np.bool)] = regions.sum(axis=0).T
    return nibabel.Nifti1Image(data, affine)


def generate_labeled_regions_large(shape, n_regions, rand_gen=None,
                                   affine=np.eye(4)):
    """Similar to generate_labeled_regions, but suitable for a large number of
    regions.

    See generate_labeled_regions for details.
    """
    if rand_gen is None:
        rand_gen = np.random.RandomState(0)
    data = rand_gen.randint(n_regions + 1, size=shape)
    if len(np.unique(data)) != n_regions + 1:
        raise ValueError("Some labels are missing. Maybe shape is too small.")
    return nibabel.Nifti1Image(data, affine)


def generate_fake_fmri(shape=(10, 11, 12), length=17, kind="noise",
                       affine=np.eye(4), n_blocks=None, block_size=None,
                       block_type='classification',
                       rand_gen=np.random.RandomState(0)):
    """Generate a signal which can be used for testing.

    The return value is a 4D array, representing 3D volumes along time.
    Only the voxels in the center are non-zero, to mimic the presence of
    brain voxels in real signals. Setting n_blocks to an integer generates
    condition blocks, the remaining of the timeseries corresponding
    to 'rest' or 'baseline' condition.

    Parameters
    ==========
    shape: tuple, optional
        Shape of 3D volume

    length: int, optional
        Number of time instants

    kind: string, optional
        Kind of signal used as timeseries.
        "noise": uniformly sampled values in [0..255]
        "step": 0.5 for the first half then 1.

    affine: numpy.ndarray
        Affine of returned images

    n_blocks: int or None
        Number of condition blocks.

    block_size: int or None
        Number of timepoints in a block. Used only if n_blocks is not
        None. Defaults to 3 if n_blocks is not None.

    block_type: str
        Defines if the returned target should be used for
        'classification' or 'regression'.

    Returns
    =======
    fmri: nibabel.Nifti1Image
        fake fmri signal.
        shape: shape + (length,)

    mask: nibabel.Nifti1Image
        mask giving non-zero voxels

    target: numpy.ndarray
        Classification or regression target. Shape of number of
        time points (length). Returned only if n_blocks is not None
    """
    full_shape = shape + (length, )
    fmri = np.zeros(full_shape)
    # Fill central voxels timeseries with random signals
    width = [s // 2 for s in shape]
    shift = [s // 4 for s in shape]

    if kind == "noise":
        signals = rand_gen.randint(256, size=(width + [length]))
    elif kind == "step":
        signals = np.ones(width + [length])
        signals[..., :length // 2] = 0.5
    else:
        raise ValueError("Unhandled value for parameter 'kind'")

    fmri[shift[0]:shift[0] + width[0],
         shift[1]:shift[1] + width[1],
         shift[2]:shift[2] + width[2],
         :] = signals

    mask = np.zeros(shape)
    mask[shift[0]:shift[0] + width[0],
         shift[1]:shift[1] + width[1],
         shift[2]:shift[2] + width[2]] = 1

    if n_blocks is None:
        return (nibabel.Nifti1Image(fmri, affine),
                nibabel.Nifti1Image(mask, affine))

    block_size = 3 if block_size is None else block_size
    flat_fmri = fmri[mask.astype(np.bool)]
    flat_fmri /= np.abs(flat_fmri).max()
    target = np.zeros(length, dtype=np.int)
    rest_max_size = (length - (n_blocks * block_size)) // n_blocks
    if rest_max_size < 0:
        raise ValueError(
            '%s is too small '
            'to put %s blocks of size %s' % (
                length, n_blocks, block_size))
    t_start = 0
    if rest_max_size > 0:
        t_start = rand_gen.random_integers(0, rest_max_size, 1)[0]
    for block in range(n_blocks):
        if block_type == 'classification':
            # Select a random voxel and add some signal to the background
            voxel_idx = rand_gen.randint(0, flat_fmri.shape[0], 1)[0]
            trials_effect = (rand_gen.random_sample(block_size) + 1) * 3.
        else:
            # Select the voxel in the image center and add some signal
            # that increases with each block
            voxel_idx = flat_fmri.shape[0] // 2
            trials_effect = (
                rand_gen.random_sample(block_size) + 1) * block
        t_rest = 0
        if rest_max_size > 0:
            t_rest = rand_gen.random_integers(0, rest_max_size, 1)[0]
        flat_fmri[voxel_idx, t_start:t_start + block_size] += trials_effect
        target[t_start:t_start + block_size] = block + 1
        t_start += t_rest + block_size
    target = target if block_type == 'classification' \
        else target.astype(np.float)
    fmri = np.zeros(fmri.shape)
    fmri[mask.astype(np.bool)] = flat_fmri
    return (nibabel.Nifti1Image(fmri, affine),
            nibabel.Nifti1Image(mask, affine), target)


def generate_signals_from_precisions(precisions,
                                     min_n_samples=50, max_n_samples=100,
                                     random_state=0):
    """Generate timeseries according to some given precision matrices.

    Signals all have zero mean.

    Parameters
    ----------
    precisions: list of numpy.ndarray
        list of precision matrices. Every matrix must be square (with the same
        size) and positive definite. The output of
        generate_group_sparse_gaussian_graphs() can be used here.

    min_samples, max_samples: int
        the number of samples drawn for each timeseries is taken at random
        between these two numbers.

    Returns
    -------
    signals: list of numpy.ndarray
        output signals. signals[n] corresponds to precisions[n], and has shape
        (sample number, precisions[n].shape[0]).
    """
    random_state = check_random_state(random_state)

    signals = []
    n_samples = random_state.randint(min_n_samples, high=max_n_samples,
                                     size=len(precisions))

    mean = np.zeros(precisions[0].shape[0])
    for n, prec in zip(n_samples, precisions):
        signals.append(random_state.multivariate_normal(mean,
                                                    np.linalg.inv(prec),
                                                    (n,)))
    return signals


def generate_group_sparse_gaussian_graphs(
        n_subjects=5, n_features=30, min_n_samples=30, max_n_samples=50,
        density=0.1, random_state=0, verbose=0):
    """Generate signals drawn from a sparse Gaussian graphical model.

    Parameters
    ==========
    n_subjects : int, optional
        number of subjects

    n_features : int, optional
        number of signals per subject to generate

    density : float, optional
        density of edges in graph topology

    min_n_samples, max_n_samples : int, optional
        Each subject have a different number of samples, between these two
        numbers. All signals for a given subject have the same number of
        samples.

    random_state : int or numpy.random.RandomState instance, optional
        random number generator, or seed.

    verbose: int, optional
        verbosity level (0 means no message).

    Returns
    =======
    subjects : list of numpy.ndarray, shape for each (n_samples, n_features)
        subjects[n] is the signals for subject n. They are provided as a numpy
        len(subjects) = n_subjects. n_samples varies according to the subject.

    precisions : list of numpy.ndarray
        precision matrices.

    topology : numpy.ndarray
        binary array giving the graph topology used for generating covariances
        and signals.
    """

    random_state = check_random_state(random_state)
    # Generate topology (upper triangular binary matrix, with zeros on the
    # diagonal)
    topology = np.empty((n_features, n_features))
    topology[:, :] = np.triu((
        random_state.randint(0, high=int(1. / density),
                             size=n_features * n_features)
    ).reshape(n_features, n_features) == 0, k=1)

    # Generate edges weights on topology
    precisions = []
    mask = topology > 0
    for _ in range(n_subjects):

        # See also sklearn.datasets.samples_generator.make_sparse_spd_matrix
        prec = topology.copy()
        prec[mask] = random_state.uniform(low=.1, high=.8, size=(mask.sum()))
        prec += np.eye(prec.shape[0])
        prec = np.dot(prec.T, prec)

        # Assert precision matrix is spd
        np.testing.assert_almost_equal(prec, prec.T)
        eigenvalues = np.linalg.eigvalsh(prec)
        if eigenvalues.min() < 0:
            raise ValueError("Failed generating a positive definite precision "
                             "matrix. Decreasing n_features can help solving "
                             "this problem.")
        precisions.append(prec)

    # Returns the topology matrix of precision matrices.
    topology += np.eye(*topology.shape)
    topology = np.dot(topology.T, topology)
    topology = topology > 0
    assert(np.all(topology == topology.T))
    logger.log("Sparsity: {0:f}".format(
        1. * topology.sum() / (topology.shape[0] ** 2)),
        verbose=verbose)

    # Generate temporal signals
    signals = generate_signals_from_precisions(precisions,
                                               min_n_samples=min_n_samples,
                                               max_n_samples=max_n_samples,
                                               random_state=random_state)
    return signals, precisions, topology


def is_nose_running():
    """Returns whether we are running the nose test loader
    """
    if 'nose' not in sys.modules:
        return
    try:
        import nose
    except ImportError:
        return False
    # Now check that we have the loader in the call stask
    stack = inspect.stack()
    from nose import loader
    loader_file_name = loader.__file__
    if loader_file_name.endswith('.pyc'):
        loader_file_name = loader_file_name[:-1]
    for _, file_name, _, _, _, _ in stack:
        if file_name == loader_file_name:
            return True
    return False


def skip_if_running_nose(msg=''):
    """ Raise a SkipTest if we appear to be running the nose test loader.

    Parameters
    ==========
    msg: string, optional
        The message issued when SkipTest is raised
    """
    if is_nose_running():
        import nose
        raise nose.SkipTest(msg)


# Backport: On some nose versions, assert_less_equal is not present
try:
    from nose.tools import assert_less_equal
except ImportError:
    def assert_less_equal(a, b):
        if a > b:
            raise AssertionError("%f is not less than %f" % (a, b))
