"""The APFS container file system implementation."""

import pyfsapfs

from dfvfs.lib import definitions
from dfvfs.lib import errors
from dfvfs.path import apfs_container_path_spec
from dfvfs.resolver import resolver
from dfvfs.vfs import apfs_container_file_entry
from dfvfs.vfs import file_system


class APFSContainerFileSystem(file_system.FileSystem):
    """APFS container file system using pyfsapfs."""

    TYPE_INDICATOR = definitions.TYPE_INDICATOR_APFS_CONTAINER

    _APFS_LOCATION_PREFIX = "/apfs"

    def __init__(self, resolver_context, path_spec):
        """Initializes an APFS container file system.

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

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

        Raises:
          OSError: if the close failed.
        """
        self._fsapfs_container = 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 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
        )

        fsapfs_container = pyfsapfs.container()
        fsapfs_container.open_file_object(file_object)

        self._file_object = file_object
        self._fsapfs_container = fsapfs_container

    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.
        """
        volume_index = self.GetVolumeIndexByPathSpec(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._fsapfs_container.number_of_volumes

    def GetAPFSContainer(self):
        """Retrieves the APFS container.

        Returns:
          pyfsapfs.container: the APFS container.
        """
        return self._fsapfs_container

    def GetAPFSVolumeByPathSpec(self, path_spec):
        """Retrieves an APFS volume for a path specification.

        Args:
          path_spec (PathSpec): path specification.

        Returns:
          pyfsapfs.volume: an APFS volume or None if not available.
        """
        volume_index = self.GetVolumeIndexByPathSpec(path_spec)
        if volume_index is None:
            return None

        return self._fsapfs_container.get_volume(volume_index)

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

        Args:
          path_spec (PathSpec): a path specification.

        Returns:
          APFSContainerFileEntry: a file entry or None if not exists.
        """
        volume_index = self.GetVolumeIndexByPathSpec(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 apfs_container_file_entry.APFSContainerFileEntry(
                self._resolver_context, self, path_spec, is_root=True, is_virtual=True
            )

        if volume_index < 0 or volume_index >= self._fsapfs_container.number_of_volumes:
            return None

        return apfs_container_file_entry.APFSContainerFileEntry(
            self._resolver_context, self, path_spec, volume_index=volume_index
        )

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

        Returns:
          APFSContainerFileEntry: a file entry.
        """
        path_spec = apfs_container_path_spec.APFSContainerPathSpec(
            location=self.LOCATION_ROOT, parent=self._path_spec.parent
        )
        return self.GetFileEntryByPathSpec(path_spec)

    def GetVolumeIndexByPathSpec(self, path_spec):
        """Retrieves the volume index for a path specification.

        Args:
          path_spec (PathSpec): path specification.

        Returns:
          int: volume index or None if the index cannot be determined.
        """
        volume_index = getattr(path_spec, "volume_index", None)
        if volume_index is not None:
            return volume_index

        location = getattr(path_spec, "location", None)
        if location is None or location[:5] != self._APFS_LOCATION_PREFIX:
            return None

        volume_index = None

        if len(location) > 6 and location[5] == "{" and location[-1] == "}":
            for index, fsapfs_volume in enumerate(self._fsapfs_container.volumes):
                if fsapfs_volume.identifier == location[6:-1]:
                    volume_index = index
                    break

        else:
            try:
                volume_index = int(location[5:], 10) - 1
            except (TypeError, ValueError):
                pass

        if volume_index is None or volume_index < 0 or volume_index > 99:
            volume_index = None

        return volume_index
