"""The HFS file system implementation."""

import pyfshfs

from dfvfs.lib import definitions
from dfvfs.lib import errors
from dfvfs.path import hfs_path_spec
from dfvfs.resolver import resolver
from dfvfs.vfs import file_system
from dfvfs.vfs import hfs_file_entry


class HFSFileSystem(file_system.FileSystem):
    """File system that uses pyfshfs."""

    ROOT_DIRECTORY_IDENTIFIER_NUMBER = 2

    TYPE_INDICATOR = definitions.TYPE_INDICATOR_HFS

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

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

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

        Raises:
          OSError: if the close failed.
        """
        self._fshfs_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.

        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
        )

        fshfs_volume = pyfshfs.volume()
        fshfs_volume.open_file_object(file_object)

        self._file_object = file_object
        self._fshfs_volume = fshfs_volume

    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.

        Raises:
          BackEndError: if the file entry cannot be opened.
        """
        # Opening a file by identifier is faster than opening a file by location.
        # but does not preserve the name of indirect nodes.
        fshfs_file_entry = None
        location = getattr(path_spec, "location", None)
        identifier = getattr(path_spec, "identifier", None)

        try:
            if location is not None:
                fshfs_file_entry = self._fshfs_volume.get_file_entry_by_path(location)
            elif identifier is not None:
                fshfs_file_entry = self._fshfs_volume.get_file_entry_by_identifier(
                    identifier
                )

        except OSError as exception:
            raise errors.BackEndError(exception)

        return fshfs_file_entry is not None

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

        Args:
          path_spec (PathSpec): path specification.

        Returns:
          HFSFileEntry: file entry or None if not available.

        Raises:
          BackEndError: if the file entry cannot be opened.
        """
        # Opening a file by identifier is faster than opening a file by location.
        # but does not preserve the name of indirect nodes.
        fshfs_file_entry = None
        location = getattr(path_spec, "location", None)
        identifier = getattr(path_spec, "identifier", None)

        if (
            location == self.LOCATION_ROOT
            or identifier == self.ROOT_DIRECTORY_IDENTIFIER_NUMBER
        ):
            fshfs_file_entry = self._fshfs_volume.get_root_directory()
            return hfs_file_entry.HFSFileEntry(
                self._resolver_context,
                self,
                path_spec,
                fshfs_file_entry=fshfs_file_entry,
                is_root=True,
            )

        try:
            if location is not None:
                fshfs_file_entry = self._fshfs_volume.get_file_entry_by_path(location)
            elif identifier is not None:
                fshfs_file_entry = self._fshfs_volume.get_file_entry_by_identifier(
                    identifier
                )

        except OSError as exception:
            raise errors.BackEndError(exception)

        if fshfs_file_entry is None:
            return None

        return hfs_file_entry.HFSFileEntry(
            self._resolver_context, self, path_spec, fshfs_file_entry=fshfs_file_entry
        )

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

        Args:
          path_spec (PathSpec): a path specification.

        Returns:
          pyfshfs.file_entry: file entry.

        Raises:
          PathSpecError: if the path specification is missing location and
              identifier.
        """
        # Opening a file by identifier is faster than opening a file by location.
        # but does not preserve the name of indirect nodes.
        location = getattr(path_spec, "location", None)
        identifier = getattr(path_spec, "identifier", None)

        if location is not None:
            fshfs_file_entry = self._fshfs_volume.get_file_entry_by_path(location)
        elif identifier is not None:
            fshfs_file_entry = self._fshfs_volume.get_file_entry_by_identifier(
                identifier
            )
        else:
            raise errors.PathSpecError(
                "Path specification missing location and identifier."
            )

        return fshfs_file_entry

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

        Returns:
          HFSFileEntry: file entry.
        """
        path_spec = hfs_path_spec.HFSPathSpec(
            location=self.LOCATION_ROOT,
            identifier=self.ROOT_DIRECTORY_IDENTIFIER_NUMBER,
            parent=self._path_spec.parent,
        )
        return self.GetFileEntryByPathSpec(path_spec)
