start introducing modules

zfs_backup/disk.py

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+from __future__ import annotations
+
+from pathlib import Path
+from uuid import UUID
+
+from .messages import ALREADY_DECRYPTED, NOT_DECRYPTED
+from .cryptsetup import Cryptsetup
+from .misc import DISK_BY_UUID
+
+
+class Disk:
+    def __init__(self, uuid: UUID, name: str):
+        self.uuid = uuid
+        self._decrypted: bool = False
+        self._was_already_decrypted: bool = False
+        self._name = name
+
+    def decrypt(self) -> None:
+        """Open a LUKS-encrypted disk with `cryptsetup`. Silently pass if it was already decrypted."""
+        if self._decrypted:
+            raise ValueError(ALREADY_DECRYPTED, self._name)
+        self._was_already_decrypted = Cryptsetup.decrypt(self._path, self._mapper_entry)
+        self._decrypted = True
+
+    @property
+    def _path(self) -> Path:
+        """Unique path of the disk using /dev/disk/by-uuid."""
+        return DISK_BY_UUID / str(self.uuid)
+
+    @property
+    def _mapper_entry(self) -> str:
+        """Name under which the decrypted disk will appear in /dev/mapper."""
+        return f"crypt-{self._name}"
+
+    def encrypt(self) -> None:
+        """Close a LUKS-encrypted container with `cryptsetup`."""
+        if not self._decrypted:
+            raise ValueError(NOT_DECRYPTED, self._name)
+        if self._was_already_decrypted:
+            return
+        Cryptsetup.encrypt(self._mapper_entry)
+        self._decrypted = False