Add an abstract base class for documents

earthsnake/__init__.py

@@ -15,3 +15,4 @@ Usage example
 __version__ = '0.1.0'
 
 from .identity import Identity
+from .document import Document

earthsnake/document/__init__.py

@@ -0,0 +1,27 @@
+"""Document handling classes"""
+
+from abc import ABC, abstractmethod
+from datetime import datetime
+from typing import Optional
+
+from ..identity import Identity
+from ..path import Path
+
+
+class Document(ABC):  # pragma: no cover pylint: disable=too-few-public-methods
+    """Abstract base class for documents"""
+
+    path: Path
+
+    author: Identity
+
+    timestamp: datetime
+
+    signature: str
+
+    @abstractmethod
+    def sign(self, identity: Optional[Identity] = None) -> None:
+        """Sign the document as identity
+
+        If ``identity`` is ``None``, use ``self.author`` instead.
+        """