from textwrap import dedent

from numpy import (
    bool_,
    dtype,
    float32,
    float64,
    int32,
    int64,
    int16,
    uint16,
    ndarray,
    uint32,
    uint8,
)
from catalyst.errors import (
    WindowLengthNotPositive,
    WindowLengthTooLong,
)
from catalyst.lib.labelarray import LabelArray
from catalyst.utils.numpy_utils import (
    datetime64ns_dtype,
    float64_dtype,
    int64_dtype,
    uint8_dtype,
)
from catalyst.utils.memoize import lazyval

# These class names are all the same because of our bootleg templating system.
from ._float64window import AdjustedArrayWindow as Float64Window
from ._int64window import AdjustedArrayWindow as Int64Window
from ._labelwindow import AdjustedArrayWindow as LabelWindow
from ._uint8window import AdjustedArrayWindow as UInt8Window


NOMASK = None
BOOL_DTYPES = frozenset(
    map(dtype, [bool_]),
)
FLOAT_DTYPES = frozenset(
    map(dtype, [float32, float64]),
)
INT_DTYPES = frozenset(
    # NOTE: uint64 not supported because it can't be safely cast to int64.
    map(dtype, [int16, uint16, int32, int64, uint32]),
)
DATETIME_DTYPES = frozenset(
    map(dtype, ['datetime64[ns]', 'datetime64[D]']),
)
# We use object arrays for strings.
OBJECT_DTYPES = frozenset(map(dtype, ['O']))
STRING_KINDS = frozenset(['S', 'U'])

REPRESENTABLE_DTYPES = BOOL_DTYPES.union(
    FLOAT_DTYPES,
    INT_DTYPES,
    DATETIME_DTYPES,
    OBJECT_DTYPES,
)


def can_represent_dtype(dtype):
    """
    Can we build an AdjustedArray for a baseline of `dtype``?
    """
    return dtype in REPRESENTABLE_DTYPES or dtype.kind in STRING_KINDS


def is_categorical(dtype):
    """
    Do we represent this dtype with LabelArrays rather than ndarrays?
    """
    return dtype in OBJECT_DTYPES or dtype.kind in STRING_KINDS


CONCRETE_WINDOW_TYPES = {
    float64_dtype: Float64Window,
    int64_dtype: Int64Window,
    uint8_dtype: UInt8Window,
}


def _normalize_array(data, missing_value):
    """
    Coerce buffer data for an AdjustedArray into a standard scalar
    representation, returning the coerced array and a dict of argument to pass
    to np.view to use when providing a user-facing view of the underlying data.

    - float* data is coerced to float64 with viewtype float64.
    - int32, int64, and uint32 are converted to int64 with viewtype int64.
    - datetime[*] data is coerced to int64 with a viewtype of datetime64[ns].
    - bool_ data is coerced to uint8 with a viewtype of bool_.

    Parameters
    ----------
    data : np.ndarray

    Returns
    -------
    coerced, view_kwargs : (np.ndarray, np.dtype)
    """
    if isinstance(data, LabelArray):
        return data, {}

    data_dtype = data.dtype
    if data_dtype == bool_:
        return data.astype(uint8), {'dtype': dtype(bool_)}
    elif data_dtype in FLOAT_DTYPES:
        return data.astype(float64), {'dtype': dtype(float64)}
    elif data_dtype in INT_DTYPES:
        return data.astype(int64), {'dtype': dtype(int64)}
    elif is_categorical(data_dtype):
        if not isinstance(missing_value, LabelArray.SUPPORTED_SCALAR_TYPES):
            raise TypeError(
                "Invalid missing_value for categorical array.\n"
                "Expected None, bytes or unicode. Got %r." % missing_value,
            )
        return LabelArray(data, missing_value), {}
    elif data_dtype.kind == 'M':
        try:
            outarray = data.astype('datetime64[ns]').view('int64')
            return outarray, {'dtype': datetime64ns_dtype}
        except OverflowError:
            raise ValueError(
                "AdjustedArray received a datetime array "
                "not representable as datetime64[ns].\n"
                "Min Date: %s\n"
                "Max Date: %s\n"
                % (data.min(), data.max())
            )
    else:
        raise TypeError(
            "Don't know how to construct AdjustedArray "
            "on data of type %s." % data_dtype
        )


class AdjustedArray(object):
    """
    An array that can be iterated with a variable-length window, and which can
    provide different views on data from different perspectives.

    Parameters
    ----------
    data : np.ndarray
        The baseline data values.
    mask : np.ndarray[bool]
        A mask indicating the locations of missing data.
    adjustments : dict[int -> list[Adjustment]]
        A dict mapping row indices to lists of adjustments to apply when we
        reach that row.
    missing_value : object
        A value to use to fill missing data in yielded windows.
        Should be a value coercible to `data.dtype`.
    """
    __slots__ = (
        '_data',
        '_view_kwargs',
        'adjustments',
        'missing_value',
        '__weakref__',
    )

    def __init__(self, data, mask, adjustments, missing_value):
        self._data, self._view_kwargs = _normalize_array(data, missing_value)

        self.adjustments = adjustments
        self.missing_value = missing_value

        if mask is not NOMASK:
            if mask.dtype != bool_:
                raise ValueError("Mask must be a bool array.")
            if data.shape != mask.shape:
                raise ValueError(
                    "Mask shape %s != data shape %s." %
                    (mask.shape, data.shape),
                )
            self._data[~mask] = self.missing_value

    @lazyval
    def data(self):
        """
        The data stored in this array.
        """
        return self._data.view(**self._view_kwargs)

    @lazyval
    def dtype(self):
        """
        The dtype of the data stored in this array.
        """
        return self._view_kwargs.get('dtype') or self._data.dtype

    @lazyval
    def _iterator_type(self):
        """
        The iterator produced when `traverse` is called on this Array.
        """
        if isinstance(self._data, LabelArray):
            return LabelWindow
        return CONCRETE_WINDOW_TYPES[self._data.dtype]

    def traverse(self,
                 window_length,
                 offset=0,
                 perspective_offset=0):
        """
        Produce an iterator rolling windows rows over our data.
        Each emitted window will have `window_length` rows.

        Parameters
        ----------
        window_length : int
            The number of rows in each emitted window.
        offset : int, optional
            Number of rows to skip before the first window.  Default is 0.
        perspective_offset : int, optional
            Number of rows past the end of the current window from which to
            "view" the underlying data.
        """
        data = self._data.copy()
        _check_window_params(data, window_length)
        return self._iterator_type(
            data,
            self._view_kwargs,
            self.adjustments,
            offset,
            window_length,
            perspective_offset,
            rounding_places=None,
        )

    def inspect(self):
        """
        Return a string representation of the data stored in this array.
        """
        return dedent(
            """\
            Adjusted Array ({dtype}):

            Data:
            {data!r}

            Adjustments:
            {adjustments}
            """
        ).format(
            dtype=self.dtype.name,
            data=self.data,
            adjustments=self.adjustments,
        )


def ensure_adjusted_array(ndarray_or_adjusted_array, missing_value):
    if isinstance(ndarray_or_adjusted_array, AdjustedArray):
        return ndarray_or_adjusted_array
    elif isinstance(ndarray_or_adjusted_array, ndarray):
        return AdjustedArray(
            ndarray_or_adjusted_array, NOMASK, {}, missing_value,
        )
    else:
        raise TypeError(
            "Can't convert %s to AdjustedArray" %
            type(ndarray_or_adjusted_array).__name__
        )


def ensure_ndarray(ndarray_or_adjusted_array):
    """
    Return the input as a numpy ndarray.

    This is a no-op if the input is already an ndarray.  If the input is an
    adjusted_array, this extracts a read-only view of its internal data buffer.

    Parameters
    ----------
    ndarray_or_adjusted_array : numpy.ndarray | catalyst.data.adjusted_array

    Returns
    -------
    out : The input, converted to an ndarray.
    """
    if isinstance(ndarray_or_adjusted_array, ndarray):
        return ndarray_or_adjusted_array
    elif isinstance(ndarray_or_adjusted_array, AdjustedArray):
        return ndarray_or_adjusted_array.data
    else:
        raise TypeError(
            "Can't convert %s to ndarray" %
            type(ndarray_or_adjusted_array).__name__
        )


def _check_window_params(data, window_length):
    """
    Check that a window of length `window_length` is well-defined on `data`.

    Parameters
    ----------
    data : np.ndarray[ndim=2]
        The array of data to check.
    window_length : int
        Length of the desired window.

    Returns
    -------
    None

    Raises
    ------
    WindowLengthNotPositive
        If window_length < 1.
    WindowLengthTooLong
        If window_length is greater than the number of rows in `data`.
    """
    if window_length < 1:
        raise WindowLengthNotPositive(window_length=window_length)

    if window_length > data.shape[0]:
        raise WindowLengthTooLong(
            nrows=data.shape[0],
            window_length=window_length,
        )
