from evalml.pipelines.components.transformers import Transformer
from evalml.utils import (
    _convert_woodwork_types_wrapper,
    _retain_custom_types_and_initalize_woodwork,
    infer_feature_types
)


def _extract_year(col, encode_as_categories=False):
    return col.dt.year, None


_month_to_int_mapping = {"January": 0, "February": 1, "March": 2, "April": 3, "May": 4, "June": 5,
                         "July": 6, "August": 7, "September": 8, "October": 9, "November": 10, "December": 11}


def _extract_month(col, encode_as_categories=False):
    months = col.dt.month_name()
    months_unique = months.unique()
    months_encoded = months.map(lambda m: _month_to_int_mapping[m])
    if encode_as_categories:
        months_encoded = months_encoded.astype("category")
    return months_encoded, {m: _month_to_int_mapping[m] for m in months_unique}


_day_to_int_mapping = {"Sunday": 0, "Monday": 1, "Tuesday": 2, "Wednesday": 3, "Thursday": 4, "Friday": 5,
                       "Saturday": 6}


def _extract_day_of_week(col, encode_as_categories=False):
    days = col.dt.day_name()
    days_unique = days.unique()
    days_encoded = days.map(lambda d: _day_to_int_mapping[d])
    if encode_as_categories:
        days_encoded = days_encoded.astype("category")
    return days_encoded, {d: _day_to_int_mapping[d] for d in days_unique}


def _extract_hour(col, encode_as_categories=False):
    return col.dt.hour, None


class DateTimeFeaturizer(Transformer):
    """Transformer that can automatically featurize DateTime columns."""
    name = "DateTime Featurization Component"
    hyperparameter_ranges = {}
    _function_mappings = {"year": _extract_year,
                          "month": _extract_month,
                          "day_of_week": _extract_day_of_week,
                          "hour": _extract_hour}

    def __init__(self, features_to_extract=None, encode_as_categories=False, random_seed=0, **kwargs):
        """Extracts features from DateTime columns

        Arguments:
            features_to_extract (list): List of features to extract. Valid options include "year", "month", "day_of_week", "hour".
            encode_as_categories (bool): Whether day-of-week and month features should be encoded as pandas "category" dtype.
                This allows OneHotEncoders to encode these features.
            random_seed (int): Seed for the random number generator. Defaults to 0.
        """
        if features_to_extract is None:
            features_to_extract = ["year", "month", "day_of_week", "hour"]
        invalid_features = set(features_to_extract) - set(self._function_mappings.keys())
        if len(invalid_features) > 0:
            raise ValueError("{} are not valid options for features_to_extract".format(", ".join([f"'{feature}'" for feature in invalid_features])))

        parameters = {"features_to_extract": features_to_extract,
                      "encode_as_categories": encode_as_categories}
        parameters.update(kwargs)

        self._date_time_col_names = None
        self._categories = {}
        self.encode_as_categories = encode_as_categories
        super().__init__(parameters=parameters,
                         component_obj=None,
                         random_seed=random_seed)

    def fit(self, X, y=None):
        X = infer_feature_types(X)
        self._date_time_col_names = X.select("datetime").columns
        return self

    def transform(self, X, y=None):
        """Transforms data X by creating new features using existing DateTime columns, and then dropping those DateTime columns

        Arguments:
            X (ww.DataTable, pd.DataFrame): Data to transform
            y (ww.DataColumn, pd.Series, optional): Ignored.

        Returns:
            ww.DataTable: Transformed X
        """
        X_ww = infer_feature_types(X)
        X_t = _convert_woodwork_types_wrapper(X_ww.to_dataframe())
        features_to_extract = self.parameters["features_to_extract"]
        if len(features_to_extract) == 0:
            return infer_feature_types(X_t)
        for col_name in self._date_time_col_names:
            for feature in features_to_extract:
                name = f"{col_name}_{feature}"
                features, categories = self._function_mappings[feature](X_t[col_name], self.encode_as_categories)
                X_t[name] = features
                if categories:
                    self._categories[name] = categories
        X_t = X_t.drop(self._date_time_col_names, axis=1)
        return _retain_custom_types_and_initalize_woodwork(X_ww, X_t)

    def get_feature_names(self):
        """Gets the categories of each datetime feature.

        Returns:
           Dictionary, where each key-value pair is a column name and a dictionary
           mapping the unique feature values to their integer encoding.
        """
        return self._categories

    def _get_feature_provenance(self):
        provenance = {}
        for col_name in self._date_time_col_names:
            provenance[col_name] = []
            for feature in self.parameters['features_to_extract']:
                provenance[col_name].append(f'{col_name}_{feature}')
        return provenance
