"""The NTFS file system implementation."""

import pyfsntfs

from dfvfs.lib import definitions
from dfvfs.lib import errors
from dfvfs.path import ntfs_path_spec
from dfvfs.resolver import resolver
from dfvfs.vfs import file_system
from dfvfs.vfs import ntfs_file_entry


class NTFSFileSystem(file_system.FileSystem):
    """File system that uses pyfsntfs."""

    MFT_ENTRY_ROOT_DIRECTORY = 5

    LOCATION_ROOT = "\\"
    PATH_SEPARATOR = "\\"

    TYPE_INDICATOR = definitions.TYPE_INDICATOR_NTFS

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

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

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

        Raises:
          OSError: if the close failed.
        """
        self._fsntfs_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
        )

        fsntfs_volume = pyfsntfs.volume()
        fsntfs_volume.open_file_object(file_object)

        self._file_object = file_object
        self._fsntfs_volume = fsntfs_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 MFT entry is faster than opening a file by location.
        # However we need the index of the corresponding $FILE_NAME MFT attribute.
        fsntfs_file_entry = None
        location = getattr(path_spec, "location", None)
        mft_attribute = getattr(path_spec, "mft_attribute", None)
        mft_entry = getattr(path_spec, "mft_entry", None)

        try:
            if mft_attribute is not None and mft_entry is not None:
                fsntfs_file_entry = self._fsntfs_volume.get_file_entry(mft_entry)
            elif location is not None:
                fsntfs_file_entry = self._fsntfs_volume.get_file_entry_by_path(location)

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

        return fsntfs_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:
          NTFSFileEntry: file entry or None if not available.

        Raises:
          BackEndError: if the file entry cannot be opened.
        """
        # Opening a file by MFT entry is faster than opening a file by location.
        # However we need the index of the corresponding $FILE_NAME MFT attribute.
        fsntfs_file_entry = None
        location = getattr(path_spec, "location", None)
        mft_attribute = getattr(path_spec, "mft_attribute", None)
        mft_entry = getattr(path_spec, "mft_entry", None)

        if location == self.LOCATION_ROOT or mft_entry == self.MFT_ENTRY_ROOT_DIRECTORY:
            fsntfs_file_entry = self._fsntfs_volume.get_root_directory()
            return ntfs_file_entry.NTFSFileEntry(
                self._resolver_context,
                self,
                path_spec,
                fsntfs_file_entry=fsntfs_file_entry,
                is_root=True,
            )

        try:
            if mft_attribute is not None and mft_entry is not None:
                fsntfs_file_entry = self._fsntfs_volume.get_file_entry(mft_entry)
            elif location is not None:
                fsntfs_file_entry = self._fsntfs_volume.get_file_entry_by_path(location)

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

        if fsntfs_file_entry is None:
            return None

        return ntfs_file_entry.NTFSFileEntry(
            self._resolver_context, self, path_spec, fsntfs_file_entry=fsntfs_file_entry
        )

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

        Args:
          path_spec (PathSpec): a path specification.

        Returns:
          pyfsntfs.file_entry: NTFS file entry.

        Raises:
          PathSpecError: if the path specification is missing location and
              MFT entry.
        """
        # Opening a file by MFT entry is faster than opening a file by location.
        # However we need the index of the corresponding $FILE_NAME MFT attribute.
        location = getattr(path_spec, "location", None)
        mft_attribute = getattr(path_spec, "mft_attribute", None)
        mft_entry = getattr(path_spec, "mft_entry", None)

        if mft_attribute is not None and mft_entry is not None:
            fsntfs_file_entry = self._fsntfs_volume.get_file_entry(mft_entry)
        elif location is not None:
            fsntfs_file_entry = self._fsntfs_volume.get_file_entry_by_path(location)
        else:
            raise errors.PathSpecError(
                "Path specification missing location and MFT entry."
            )

        return fsntfs_file_entry

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

        Returns:
          NTFSFileEntry: file entry.
        """
        path_spec = ntfs_path_spec.NTFSPathSpec(
            location=self.LOCATION_ROOT,
            mft_entry=self.MFT_ENTRY_ROOT_DIRECTORY,
            parent=self._path_spec.parent,
        )
        return self.GetFileEntryByPathSpec(path_spec)
