"""The file object file input/output (IO) object implementation."""

import abc
import os

from dfvfs.file_io import file_io


class FileObjectIO(file_io.FileIO):
    """Base class for file object-based file input/output (IO) object."""

    # pylint: disable=redundant-returns-doc

    def __init__(self, resolver_context, path_spec):
        """Initializes a file input/output (IO) object.

        Args:
          resolver_context (Context): resolver context.
          path_spec (PathSpec): a path specification.
        """
        super().__init__(resolver_context, path_spec)
        self._file_object = None
        self._size = None

    def _Close(self):
        """Closes the file-like object."""
        self._file_object.close()
        self._file_object = None

    def _Open(self):
        """Opens the file-like object defined by path specification.

        Raises:
          AccessError: if the access to open the file was denied.
          OSError: if the file-like object could not be opened.
          PathSpecError: if the path specification is incorrect.
        """
        self._file_object = self._OpenFileObject(self._path_spec)
        if not self._file_object:
            raise OSError("Unable to open missing file-like object.")

    # pylint: disable=redundant-returns-doc
    @abc.abstractmethod
    def _OpenFileObject(self, path_spec):
        """Opens the file-like object defined by path specification.

        Args:
          path_spec (PathSpec): path specification.

        Returns:
          FileIO: a file-like object.

        Raises:
          PathSpecError: if the path specification is incorrect.
        """

    # Note: that the following functions do not follow the style guide
    # because they are part of the file-like object interface.
    # pylint: disable=invalid-name

    def read(self, size=None):
        """Reads a byte string from the file-like object at the current offset.

        The function will read a byte string of the specified size or
        all of the remaining data if no size was specified.

        Args:
          size (Optional[int]): number of bytes to read, where None is all
              remaining data.

        Returns:
          bytes: data read.

        Raises:
          OSError: if the read failed.
        """
        if not self._is_open:
            raise OSError("Not opened.")

        # Do not pass the size argument as a keyword argument since it breaks
        # some file-like object implementations.
        return self._file_object.read(size)

    def seek(self, offset, whence=os.SEEK_SET):
        """Seeks to an offset within the file-like object.

        Args:
          offset (int): offset to seek to.
          whence (Optional(int)): value that indicates whether offset is an absolute
              or relative position within the file.

        Raises:
          OSError: if the seek failed.
        """
        if not self._is_open:
            raise OSError("Not opened.")

        self._file_object.seek(offset, whence)

    def get_offset(self):
        """Retrieves the current offset into the file-like object.

        Returns:
          int: current offset into the file-like object.

        Raises:
          OSError: if the file-like object has not been opened.
        """
        if not self._is_open:
            raise OSError("Not opened.")

        if not hasattr(self._file_object, "get_offset"):
            return self._file_object.tell()
        return self._file_object.get_offset()

    def get_size(self):
        """Retrieves the size of the file-like object.

        Returns:
          int: size of the file-like object data.

        Raises:
          OSError: if the file-like object has not been opened.
        """
        if not self._is_open:
            raise OSError("Not opened.")

        if not hasattr(self._file_object, "get_size"):
            if not self._size:
                current_offset = self.get_offset()
                self.seek(0, os.SEEK_END)
                self._size = self.get_offset()
                self.seek(current_offset, os.SEEK_SET)
            return self._size

        return self._file_object.get_size()
