"""The GUID Partition Table (GPT) file system implementation."""

import pyvsgpt

from dfvfs.lib import definitions
from dfvfs.lib import errors
from dfvfs.path import gpt_path_spec
from dfvfs.resolver import resolver
from dfvfs.vfs import file_system
from dfvfs.vfs import gpt_file_entry


class GPTFileSystem(file_system.FileSystem):
    """File system that uses pyvsgpt."""

    TYPE_INDICATOR = definitions.TYPE_INDICATOR_GPT

    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._file_object = None
        self._vsgpt_volume = None

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

        Raises:
          OSError: if the close failed.
        """
        self._vsgpt_volume.close()
        self._vsgpt_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
        )

        vsgpt_volume = pyvsgpt.volume()
        vsgpt_volume.open_file_object(file_object)

        self._file_object = file_object
        self._vsgpt_volume = vsgpt_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.
        """
        entry_index = self.GetEntryIndexByPathSpec(path_spec)

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

        return self._vsgpt_volume.has_partition_with_identifier(entry_index)

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

        Args:
          path_spec (PathSpec): path specification.

        Returns:
          int: entry index or None if not available.
        """
        entry_index = getattr(path_spec, "entry_index", None)
        if entry_index is not None:
            return entry_index

        location = getattr(path_spec, "location", None)
        if location is None:
            return None

        entry_index = None

        if location[:5] == "/gpt{" and location[-1] == "}":
            for vsgpt_partition in iter(self._vsgpt_volume.partitions):
                if vsgpt_partition.identifier == location[5:-1]:
                    entry_index = vsgpt_partition.entry_index

        elif location[:2] == "/p":
            try:
                entry_index = int(location[2:], 10) - 1
            except ValueError:
                pass

        if entry_index is None or entry_index < 0:
            return None

        return entry_index

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

        Args:
          path_spec (PathSpec): path specification.

        Returns:
          GPTFileEntry: a file entry or None if not available.
        """
        entry_index = self.GetEntryIndexByPathSpec(path_spec)

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

            return gpt_file_entry.GPTFileEntry(
                self._resolver_context, self, path_spec, is_root=True, is_virtual=True
            )

        if not self._vsgpt_volume.has_partition_with_identifier(entry_index):
            return None

        return gpt_file_entry.GPTFileEntry(
            self._resolver_context, self, path_spec, entry_index=entry_index
        )

    def GetGPTPartitionByPathSpec(self, path_spec):
        """Retrieves a GPT partition for a path specification.

        Args:
          path_spec (PathSpec): path specification.

        Returns:
          pyvsgpt.partition: a GPT partition or None if not available.
        """
        entry_index = self.GetEntryIndexByPathSpec(path_spec)
        if entry_index is None:
            return None

        return self._vsgpt_volume.get_partition_by_identifier(entry_index)

    def GetGPTVolume(self):
        """Retrieves the GPT volume.

        Returns:
          pyvsgpt.volume: a GPT volume.
        """
        return self._vsgpt_volume

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

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