from functools import wraps

import pandas as pd
import numpy as np

from statsmodels.tools.data import _is_using_pandas
from statsmodels.tsa.tsatools import freq_to_period


def _get_pandas_wrapper(X, trim_head=None, trim_tail=None, names=None):
    index = X.index
    #TODO: allow use index labels
    if trim_head is None and trim_tail is None:
        index = index
    elif trim_tail is None:
        index = index[trim_head:]
    elif trim_head is None:
        index = index[:-trim_tail]
    else:
        index = index[trim_head:-trim_tail]
    if hasattr(X, "columns"):
        if names is None:
            names = X.columns
        return lambda x : X.__class__(x, index=index, columns=names)
    else:
        if names is None:
            names = X.name
        return lambda x : X.__class__(x, index=index, name=names)


def _maybe_get_pandas_wrapper(X, trim_head=None, trim_tail=None):
    """
    If using pandas returns a function to wrap the results, e.g., wrapper(X)
    trim is an integer for the symmetric truncation of the series in some
    filters.
    otherwise returns None
    """
    if _is_using_pandas(X, None):
        return _get_pandas_wrapper(X, trim_head, trim_tail)
    else:
        return lambda x : x


def _maybe_get_pandas_wrapper_freq(X, trim=None):
    if _is_using_pandas(X, None):
        index = X.index
        func = _get_pandas_wrapper(X, trim)
        freq = index.inferred_freq
        return func, freq
    else:
        return lambda x : x, None


def pandas_wrapper(func, trim_head=None, trim_tail=None, names=None, *args,
                   **kwargs):
    @wraps(func)
    def new_func(X, *args, **kwargs):
        # quick pass-through for do nothing case
        if not _is_using_pandas(X, None):
            return func(X, *args, **kwargs)

        wrapper_func = _get_pandas_wrapper(X, trim_head, trim_tail,
                                           names)
        ret = func(X, *args, **kwargs)
        ret = wrapper_func(ret)
        return ret

    return new_func


def pandas_wrapper_bunch(func, trim_head=None, trim_tail=None,
                         names=None, *args, **kwargs):
    @wraps(func)
    def new_func(X, *args, **kwargs):
        # quick pass-through for do nothing case
        if not _is_using_pandas(X, None):
            return func(X, *args, **kwargs)

        wrapper_func = _get_pandas_wrapper(X, trim_head, trim_tail,
                                           names)
        ret = func(X, *args, **kwargs)
        ret = wrapper_func(ret)
        return ret

    return new_func


def pandas_wrapper_predict(func, trim_head=None, trim_tail=None,
                           columns=None, *args, **kwargs):
    raise NotImplementedError


def pandas_wrapper_freq(func, trim_head=None, trim_tail=None,
                        freq_kw='freq', columns=None, *args, **kwargs):
    """
    Return a new function that catches the incoming X, checks if it's pandas,
    calls the functions as is. Then wraps the results in the incoming index.

    Deals with frequencies. Expects that the function returns a tuple,
    a Bunch object, or a pandas-object.
    """

    @wraps(func)
    def new_func(X, *args, **kwargs):
        # quick pass-through for do nothing case
        if not _is_using_pandas(X, None):
            return func(X, *args, **kwargs)

        wrapper_func = _get_pandas_wrapper(X, trim_head, trim_tail,
                                           columns)
        index = X.index
        freq = index.inferred_freq
        kwargs.update({freq_kw : freq_to_period(freq)})
        ret = func(X, *args, **kwargs)
        ret = wrapper_func(ret)
        return ret

    return new_func


def dummy_func(X):
    return X


def dummy_func_array(X):
    return X.values


def dummy_func_pandas_columns(X):
    return X.values


def dummy_func_pandas_series(X):
    return X['A']


def test_pandas_freq_decorator():
    X = pd.util.testing.makeDataFrame()
    # in X, get a function back that returns an X with the same columns
    func = pandas_wrapper(dummy_func)

    np.testing.assert_equal(func(X.values), X)

    func = pandas_wrapper(dummy_func_array)
    pd.util.testing.assert_frame_equal(func(X), X)

    expected = X.rename(columns=dict(zip('ABCD', 'EFGH')))
    func = pandas_wrapper(dummy_func_array, names=list('EFGH'))
    pd.util.testing.assert_frame_equal(func(X), expected)