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"""``MemoryDataSet`` is a data set implementation which handles in-memory data.
"""

import copy
from typing import Any, Dict

import numpy as np
import pandas as pd

from kedro.io.core import AbstractDataSet, DataSetError


class MemoryDataSet(AbstractDataSet):
    """``MemoryDataSet`` loads and saves data from/to an in-memory\
    Python object.

    Example:
    ::

        >>> from kedro.io import MemoryDataSet
        >>> import pandas as pd
        >>>
        >>> data = pd.DataFrame({'col1': [1, 2], 'col2': [4, 5],
        >>>                      'col3': [5, 6]})
        >>> data_set = MemoryDataSet(data=data)
        >>>
        >>> loaded_data = data_set.load()
        >>> assert loaded_data.equals(data)
        >>>
        >>> new_data = pd.DataFrame({'col1': [1, 2], 'col2': [4, 5]})
        >>> data_set.save(new_data)
        >>> reloaded_data = data_set.load()
        >>> assert reloaded_data.equals(new_data)

    """

    def _describe(self) -> Dict[str, Any]:
        if self._data is not None:
            return dict(data="<{}>".format(type(self._data).__name__))
        return dict(data=None)  # pragma: no cover

    def __init__(self, data: Any = None):
        """Creates a new instance of ``MemoryDataSet`` pointing to the
        provided Python object.

        Args:
            data: Python object containing the data.
        """
        self._data = None
        if data is not None:
            self._save(data)

    def _load(self) -> Any:
        if self._data is None:
            raise DataSetError("Data for MemoryDataSet has not been saved yet.")
        if isinstance(self._data, (pd.DataFrame, np.ndarray)):
            data = self._data.copy()
        elif type(self._data).__name__ == "DataFrame":
            data = self._data
        else:
            data = copy.deepcopy(self._data)
        return data

    def _save(self, data: Any):
        if isinstance(data, (pd.DataFrame, np.ndarray)):
            self._data = data.copy()
        elif type(data).__name__ == "DataFrame":
            self._data = data
        else:
            self._data = copy.deepcopy(data)

    def _exists(self) -> bool:
        if self._data is None:
            return False
        return True

    def _release(self) -> None:
        self._data = None
