"""The SleuthKit (TSK) partition file system implementation."""

import pytsk3

from dfvfs.lib import definitions
from dfvfs.lib import errors
from dfvfs.lib import tsk_image
from dfvfs.lib import tsk_partition
from dfvfs.path import tsk_partition_path_spec
from dfvfs.resolver import resolver
from dfvfs.vfs import file_system
from dfvfs.vfs import tsk_partition_file_entry


class TSKPartitionFileSystem(file_system.FileSystem):
    """Class that implements a file system object using pytsk3."""

    TYPE_INDICATOR = definitions.TYPE_INDICATOR_TSK_PARTITION

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

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

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

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

    def _Open(self, mode="rb"):
        """Opens the file system object 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 object 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.")

        file_object = resolver.Resolver.OpenFileObject(
            self._path_spec.parent, resolver_context=self._resolver_context
        )
        tsk_image_object = tsk_image.TSKFileSystemImage(
            file_object, sector_size=self._path_spec.sector_size
        )
        tsk_volume = pytsk3.Volume_Info(tsk_image_object)

        self._file_object = file_object
        self._tsk_volume = tsk_volume

    def FileEntryExistsByPathSpec(self, path_spec):
        """Determines if a file entry for a path specification exists.

        Args:
          path_spec (PathSpec): a path specification.

        Returns:
          bool: True if the file entry exists or false otherwise.
        """
        tsk_vs_part, _ = tsk_partition.GetTSKVsPartByPathSpec(
            self._tsk_volume, path_spec
        )
        # The virtual root file has no corresponding TSK volume system part object but
        # should have a location.
        if tsk_vs_part is None:
            location = getattr(path_spec, "location", None)
            return location is not None and location == self.LOCATION_ROOT

        return True

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

        Args:
          path_spec (PathSpec): a path specification.

        Returns:
          TSKPartitionFileEntry: a file entry or None of not available.
        """
        tsk_vs_part, partition_index = tsk_partition.GetTSKVsPartByPathSpec(
            self._tsk_volume, path_spec
        )
        location = getattr(path_spec, "location", None)

        # The virtual root file has no corresponding TSK volume system part object but
        # should have a location.
        if tsk_vs_part is None:
            if location is None or location != self.LOCATION_ROOT:
                return None

            return tsk_partition_file_entry.TSKPartitionFileEntry(
                self._resolver_context, self, path_spec, is_root=True, is_virtual=True
            )

        if location is None and partition_index is not None:
            path_spec.location = f"/p{partition_index:d}"

        return tsk_partition_file_entry.TSKPartitionFileEntry(
            self._resolver_context, self, path_spec
        )

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

        Returns:
          TSKPartitionFileEntry: a file entry or None of not available.
        """
        path_spec = tsk_partition_path_spec.TSKPartitionPathSpec(
            location=self.LOCATION_ROOT, parent=self._path_spec.parent
        )
        return self.GetFileEntryByPathSpec(path_spec)

    def GetTSKVolume(self):
        """Retrieves the TSK volume object.

        Returns:
          pytsk3.Volume_Info: a TSK volume object.
        """
        return self._tsk_volume
