""" Basic functions for manipulating 2d arrays

"""
from __future__ import division, absolute_import, print_function

import functools

from numpy.core.numeric import (
    absolute, asanyarray, arange, zeros, greater_equal, multiply, ones,
    asarray, where, int8, int16, int32, int64, empty, promote_types, diagonal,
    nonzero
    )
from numpy.core.overrides import set_module
from numpy.core import overrides
from numpy.core import iinfo, transpose


__all__ = [
    'diag', 'diagflat', 'eye', 'fliplr', 'flipud', 'tri', 'triu',
    'tril', 'vander', 'histogram2d', 'mask_indices', 'tril_indices',
    'tril_indices_from', 'triu_indices', 'triu_indices_from', ]


array_function_dispatch = functools.partial(
    overrides.array_function_dispatch, module='numpy')


i1 = iinfo(int8)
i2 = iinfo(int16)
i4 = iinfo(int32)


def _min_int(low, high):
    """ get small int that fits the range """
    if high <= i1.max and low >= i1.min:
        return int8
    if high <= i2.max and low >= i2.min:
        return int16
    if high <= i4.max and low >= i4.min:
        return int32
    return int64


def _flip_dispatcher(m):
    return (m,)


@array_function_dispatch(_flip_dispatcher)
def fliplr(m):
    """
    Flip array in the left/right direction.

    Flip the entries in each row in the left/right direction.
    Columns are preserved, but appear in a different order than before.

    Parameters
    ----------
    m : array_like
        Input array, must be at least 2-D.

    Returns
    -------
    f : ndarray
        A view of `m` with the columns reversed.  Since a view
        is returned, this operation is :math:`\\mathcal O(1)`.

    See Also
    --------
    flipud : Flip array in the up/down direction.
    rot90 : Rotate array counterclockwise.

    Notes
    -----
    Equivalent to m[:,::-1]. Requires the array to be at least 2-D.

    Examples
    --------
    >>> A = np.diag([1.,2.,3.])
    >>> A
    array([[ 1.,  0.,  0.],
           [ 0.,  2.,  0.],
           [ 0.,  0.,  3.]])
    >>> np.fliplr(A)
    array([[ 0.,  0.,  1.],
           [ 0.,  2.,  0.],
           [ 3.,  0.,  0.]])

    >>> A = np.random.randn(2,3,5)
    >>> np.all(np.fliplr(A) == A[:,::-1,...])
    True

    """
    m = asanyarray(m)
    if m.ndim < 2:
        raise ValueError("Input must be >= 2-d.")
    return m[:, ::-1]


@array_function_dispatch(_flip_dispatcher)
def flipud(m):
    """
    Flip array in the up/down direction.

    Flip the entries in each column in the up/down direction.
    Rows are preserved, but appear in a different order than before.

    Parameters
    ----------
    m : array_like
        Input array.

    Returns
    -------
    out : array_like
        A view of `m` with the rows reversed.  Since a view is
        returned, this operation is :math:`\\mathcal O(1)`.

    See Also
    --------
    fliplr : Flip array in the left/right direction.
    rot90 : Rotate array counterclockwise.

    Notes
    -----
    Equivalent to ``m[::-1,...]``.
    Does not require the array to be two-dimensional.

    Examples
    --------
    >>> A = np.diag([1.0, 2, 3])
    >>> A
    array([[ 1.,  0.,  0.],
           [ 0.,  2.,  0.],
           [ 0.,  0.,  3.]])
    >>> np.flipud(A)
    array([[ 0.,  0.,  3.],
           [ 0.,  2.,  0.],
           [ 1.,  0.,  0.]])

    >>> A = np.random.randn(2,3,5)
    >>> np.all(np.flipud(A) == A[::-1,...])
    True

    >>> np.flipud([1,2])
    array([2, 1])

    """
    m = asanyarray(m)
    if m.ndim < 1:
        raise ValueError("Input must be >= 1-d.")
    return m[::-1, ...]


@set_module('numpy')
def eye(N, M=None, k=0, dtype=float, order='C'):
    """
    Return a 2-D array with ones on the diagonal and zeros elsewhere.

    Parameters
    ----------
    N : int
      Number of rows in the output.
    M : int, optional
      Number of columns in the output. If None, defaults to `N`.
    k : int, optional
      Index of the diagonal: 0 (the default) refers to the main diagonal,
      a positive value refers to an upper diagonal, and a negative value
      to a lower diagonal.
    dtype : data-type, optional
      Data-type of the returned array.
    order : {'C', 'F'}, optional
        Whether the output should be stored in row-major (C-style) or
        column-major (Fortran-style) order in memory.

        .. versionadded:: 1.14.0

    Returns
    -------
    I : ndarray of shape (N,M)
      An array where all elements are equal to zero, except for the `k`-th
      diagonal, whose values are equal to one.

    See Also
    --------
    identity : (almost) equivalent function
    diag : diagonal 2-D array from a 1-D array specified by the user.

    Examples
    --------
    >>> np.eye(2, dtype=int)
    array([[1, 0],
           [0, 1]])
    >>> np.eye(3, k=1)
    array([[ 0.,  1.,  0.],
           [ 0.,  0.,  1.],
           [ 0.,  0.,  0.]])

    """
    if M is None:
        M = N
    m = zeros((N, M), dtype=dtype, order=order)
    if k >= M:
        return m
    if k >= 0:
        i = k
    else:
        i = (-k) * M
    m[:M-k].flat[i::M+1] = 1
    return m


def _diag_dispatcher(v, k=None):
    return (v,)


@array_function_dispatch(_diag_dispatcher)
def diag(v, k=0):
    """
    Extract a diagonal or construct a diagonal array.

    See the more detailed documentation for ``numpy.diagonal`` if you use this
    function to extract a diagonal and wish to write to the resulting array;
    whether it returns a copy or a view depends on what version of numpy you
    are using.

    Parameters
    ----------
    v : array_like
        If `v` is a 2-D array, return a copy of its `k`-th diagonal.
        If `v` is a 1-D array, return a 2-D array with `v` on the `k`-th
        diagonal.
    k : int, optional
        Diagonal in question. The default is 0. Use `k>0` for diagonals
        above the main diagonal, and `k<0` for diagonals below the main
        diagonal.

    Returns
    -------
    out : ndarray
        The extracted diagonal or constructed diagonal array.

    See Also
    --------
    diagonal : Return specified diagonals.
    diagflat : Create a 2-D array with the flattened input as a diagonal.
    trace : Sum along diagonals.
    triu : Upper triangle of an array.
    tril : Lower triangle of an array.

    Examples
    --------
    >>> x = np.arange(9).reshape((3,3))
    >>> x
    array([[0, 1, 2],
           [3, 4, 5],
           [6, 7, 8]])

    >>> np.diag(x)
    array([0, 4, 8])
    >>> np.diag(x, k=1)
    array([1, 5])
    >>> np.diag(x, k=-1)
    array([3, 7])

    >>> np.diag(np.diag(x))
    array([[0, 0, 0],
           [0, 4, 0],
           [0, 0, 8]])

    """
    v = asanyarray(v)
    s = v.shape
    if len(s) == 1:
        n = s[0]+abs(k)
        res = zeros((n, n), v.dtype)
        if k >= 0:
            i = k
        else:
            i = (-k) * n
        res[:n-k].flat[i::n+1] = v
        return res
    elif len(s) == 2:
        return diagonal(v, k)
    else:
        raise ValueError("Input must be 1- or 2-d.")


@array_function_dispatch(_diag_dispatcher)
def diagflat(v, k=0):
    """
    Create a two-dimensional array with the flattened input as a diagonal.

    Parameters
    ----------
    v : array_like
        Input data, which is flattened and set as the `k`-th
        diagonal of the output.
    k : int, optional
        Diagonal to set; 0, the default, corresponds to the "main" diagonal,
        a positive (negative) `k` giving the number of the diagonal above
        (below) the main.

    Returns
    -------
    out : ndarray
        The 2-D output array.

    See Also
    --------
    diag : MATLAB work-alike for 1-D and 2-D arrays.
    diagonal : Return specified diagonals.
    trace : Sum along diagonals.

    Examples
    --------
    >>> np.diagflat([[1,2], [3,4]])
    array([[1, 0, 0, 0],
           [0, 2, 0, 0],
           [0, 0, 3, 0],
           [0, 0, 0, 4]])

    >>> np.diagflat([1,2], 1)
    array([[0, 1, 0],
           [0, 0, 2],
           [0, 0, 0]])

    """
    try:
        wrap = v.__array_wrap__
    except AttributeError:
        wrap = None
    v = asarray(v).ravel()
    s = len(v)
    n = s + abs(k)
    res = zeros((n, n), v.dtype)
    if (k >= 0):
        i = arange(0, n-k)
        fi = i+k+i*n
    else:
        i = arange(0, n+k)
        fi = i+(i-k)*n
    res.flat[fi] = v
    if not wrap:
        return res
    return wrap(res)