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"""``TextDataSet`` loads/saves data from/to a text file using an underlying
filesystem (e.g.: local, S3, GCS).
"""
from copy import deepcopy
from pathlib import PurePosixPath
from typing import Any, Dict

import fsspec

from kedro.io.core import (
    AbstractVersionedDataSet,
    DataSetError,
    Version,
    get_filepath_str,
    get_protocol_and_path,
)


class TextDataSet(AbstractVersionedDataSet):
    """``TextDataSet`` loads/saves data from/to a text file using an underlying
    filesystem (e.g.: local, S3, GCS)

    Example:
    ::

        >>> from kedro.extras.datasets.text import TextDataSet
        >>>
        >>> string_to_write = "This will go in a file."
        >>>
        >>> # data_set = TextDataSet(filepath="gcs://bucket/test.md")
        >>> data_set = TextDataSet(filepath="test.md")
        >>> data_set.save(string_to_write)
        >>> reloaded = data_set.load()
        >>> assert string_to_write == reloaded

    """

    def __init__(
        self,
        filepath: str,
        version: Version = None,
        credentials: Dict[str, Any] = None,
        fs_args: Dict[str, Any] = None,
    ) -> None:
        """Creates a new instance of ``TextDataSet`` pointing to a concrete text file
        on a specific filesystem.

        Args:
            filepath: Filepath to a text file prefixed with a protocol like `s3://`.
                If prefix is not provided, `file` protocol (local filesystem) will be used.
                The prefix should be any protocol supported by ``fsspec``.
                Note: `http(s)` doesn't support versioning.
            version: If specified, should be an instance of
                ``kedro.io.core.Version``. If its ``load`` attribute is
                None, the latest version will be loaded. If its ``save``
                attribute is None, save version will be autogenerated.
            credentials: Credentials required to get access to the underlying filesystem.
                E.g. for ``GCSFileSystem`` it should look like `{"token": None}`.
            fs_args: Extra arguments to pass into underlying filesystem class constructor
                (e.g. `{"project": "my-project"}` for ``GCSFileSystem``), as well as
                to pass to the filesystem's `open` method through nested keys
                `open_args_load` and `open_args_save`.
                Here you can find all available arguments for `open`:
                https://filesystem-spec.readthedocs.io/en/latest/api.html#fsspec.spec.AbstractFileSystem.open
                All defaults are preserved, except `mode`, which is set to `r` when loading
                and to `w` when saving.
        """
        _fs_args = deepcopy(fs_args) or {}
        _fs_open_args_load = _fs_args.pop("open_args_load", {})
        _fs_open_args_save = _fs_args.pop("open_args_save", {})
        _credentials = deepcopy(credentials) or {}

        protocol, path = get_protocol_and_path(filepath, version)

        self._protocol = protocol
        self._fs = fsspec.filesystem(self._protocol, **_credentials, **_fs_args)

        super().__init__(
            filepath=PurePosixPath(path),
            version=version,
            exists_function=self._fs.exists,
            glob_function=self._fs.glob,
        )

        _fs_open_args_load.setdefault("mode", "r")
        _fs_open_args_save.setdefault("mode", "w")
        self._fs_open_args_load = _fs_open_args_load
        self._fs_open_args_save = _fs_open_args_save

    def _describe(self) -> Dict[str, Any]:
        return dict(
            filepath=self._filepath, protocol=self._protocol, version=self._version,
        )

    def _load(self) -> str:
        load_path = get_filepath_str(self._get_load_path(), self._protocol)

        with self._fs.open(load_path, **self._fs_open_args_load) as fs_file:
            return fs_file.read()

    def _save(self, data: str) -> None:
        save_path = get_filepath_str(self._get_save_path(), self._protocol)

        with self._fs.open(save_path, **self._fs_open_args_save) as fs_file:
            fs_file.write(data)

        self._invalidate_cache()

    def _exists(self) -> bool:
        try:
            load_path = get_filepath_str(self._get_load_path(), self._protocol)
        except DataSetError:
            return False

        return self._fs.exists(load_path)

    def _release(self) -> None:
        super()._release()
        self._invalidate_cache()

    def _invalidate_cache(self) -> None:
        """Invalidate underlying filesystem caches."""
        filepath = get_filepath_str(self._filepath, self._protocol)
        self._fs.invalidate_cache(filepath)
