"""The Core Storage (CS) file system implementation."""

import pyfvde

from dfvfs.lib import cs_helper
from dfvfs.lib import definitions
from dfvfs.lib import errors
from dfvfs.path import cs_path_spec
from dfvfs.resolver import resolver
from dfvfs.vfs import cs_file_entry
from dfvfs.vfs import file_system


class CSFileSystem(file_system.FileSystem):
    """File system that uses pyfvde."""

    TYPE_INDICATOR = definitions.TYPE_INDICATOR_CS

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

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

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

        Raises:
          OSError: if the close failed.
        """
        self._fvde_volume_group = None
        self._fvde_volume.close()
        self._fvde_volume = None
        self._file_object = 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'
              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.")

        resolver.Resolver.key_chain.ExtractCredentialsFromPathSpec(self._path_spec)

        file_object = resolver.Resolver.OpenFileObject(
            self._path_spec.parent, resolver_context=self._resolver_context
        )

        fvde_volume = pyfvde.volume()

        encrypted_root_plist = resolver.Resolver.key_chain.GetCredential(
            self._path_spec, "encrypted_root_plist"
        )
        if encrypted_root_plist:
            fvde_volume.read_encrypted_root_plist(encrypted_root_plist)

        fvde_volume.open_file_object(file_object)
        # TODO: implement multi physical volume support.
        fvde_volume.open_physical_volume_files_as_file_objects([file_object])
        fvde_volume_group = fvde_volume.get_volume_group()

        self._file_object = file_object
        self._fvde_volume = fvde_volume
        self._fvde_volume_group = fvde_volume_group

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

        Args:
          path_spec (PathSpec): path specification.

        Returns:
          bool: True if the file entry exists.
        """
        volume_index = cs_helper.CSPathSpecGetVolumeIndex(path_spec)

        # The virtual root file has no corresponding volume index but
        # should have a location.
        if volume_index is None:
            location = getattr(path_spec, "location", None)
            return location is not None and location == self.LOCATION_ROOT

        return 0 <= volume_index < self._fvde_volume_group.number_of_logical_volumes

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

        Args:
          path_spec (PathSpec): path specification.

        Returns:
          CSFileEntry: a file entry or None if not available.
        """
        volume_index = cs_helper.CSPathSpecGetVolumeIndex(path_spec)

        # The virtual root file has no corresponding volume index but
        # should have a location.
        if volume_index is None:
            location = getattr(path_spec, "location", None)
            if location is None or location != self.LOCATION_ROOT:
                return None

            return cs_file_entry.CSFileEntry(
                self._resolver_context, self, path_spec, is_root=True, is_virtual=True
            )

        if (
            volume_index < 0
            or volume_index >= self._fvde_volume_group.number_of_logical_volumes
        ):
            return None

        return cs_file_entry.CSFileEntry(self._resolver_context, self, path_spec)

    def GetFVDELogicalVolumeByPathSpec(self, path_spec):
        """Retrieves a Core Storage logical volume for a path specification.

        Args:
          path_spec (PathSpec): path specification.

        Returns:
          pyfvde.logical_volume: a Core Storage logical volume or None if not
              available.
        """
        volume_index = cs_helper.CSPathSpecGetVolumeIndex(path_spec)
        if volume_index is None:
            return None

        return self._fvde_volume_group.get_logical_volume(volume_index)

    def GetFVDEVolumeGroup(self):
        """Retrieves the Core Storage volume group.

        Returns:
          pyfvde.volume_group: a Core Storage volume group.
        """
        return self._fvde_volume_group

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

        Returns:
          CSFileEntry: root file entry or None if not available.
        """
        path_spec = cs_path_spec.CSPathSpec(
            location=self.LOCATION_ROOT, parent=self._path_spec.parent
        )
        return self.GetFileEntryByPathSpec(path_spec)
