"""The compressed stream file system implementation."""

from dfvfs.lib import definitions
from dfvfs.lib import errors
from dfvfs.path import compressed_stream_path_spec
from dfvfs.vfs import compressed_stream_file_entry
from dfvfs.vfs import root_only_file_system


class CompressedStreamFileSystem(root_only_file_system.RootOnlyFileSystem):
    """Compressed stream file system."""

    TYPE_INDICATOR = definitions.TYPE_INDICATOR_COMPRESSED_STREAM

    def __init__(self, resolver_context, path_spec):
        """Initializes a compressed stream file system.

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

    def _Close(self):
        """Closes the file system.

        Raises:
          OSError: if the close failed.
        """
        self._compression_method = None

    def _Open(self, mode="rb"):
        """Opens the file system defined by path specification.

        Args:
          mode (Optional[str]): file access mode. The default is 'rb' which
              represents read-only binary.

        Raises:
          AccessError: if the access to open the file was denied.
          OSError: if the file system could not be opened.
          PathSpecError: if the path specification is incorrect.
          ValueError: if the path specification is invalid.
        """
        if not self._path_spec.HasParent():
            raise errors.PathSpecError("Unsupported path specification without parent.")

        compression_method = getattr(self._path_spec, "compression_method", None)
        if not compression_method:
            raise errors.PathSpecError(
                "Unsupported path specification without compression method."
            )

        self._compression_method = compression_method

    def GetFileEntryByPathSpec(self, path_spec):
        """Retrieves a file entry for a path specification.

        Args:
          path_spec (PathSpec): a path specification.

        Returns:
          CompressedStreamFileEntry: a file entry or None if not available.
        """
        return compressed_stream_file_entry.CompressedStreamFileEntry(
            self._resolver_context, self, path_spec, is_root=True, is_virtual=True
        )

    def GetRootFileEntry(self):
        """Retrieves the root file entry.

        Returns:
          CompressedStreamFileEntry: a file entry or None if not available.
        """
        path_spec = compressed_stream_path_spec.CompressedStreamPathSpec(
            compression_method=self._compression_method, parent=self._path_spec.parent
        )
        return self.GetFileEntryByPathSpec(path_spec)
