Add tree data object

trovedb/tree.py

@@ -0,0 +1,37 @@
+"""
+tree.py — Tree object interface for Trove.
+
+A tree is a named mapping of entries to UUIDs, serialized as UTF-8 JSON.
+Corresponds to a 'tree' row in the objects table; this class handles
+only the data field — storage is the caller's concern.
+"""
+
+import json
+
+
+class Tree:
+    def __init__(self, data: bytes | None = None):
+        """
+        Initialize a Tree. If data is provided, deserialize from UTF-8 JSON bytes.
+        An empty Tree is created if data is None.
+        """
+        if data is None:
+            self._entries: dict[str, str] = {}
+        else:
+            self._entries = json.loads(data.decode("utf-8"))
+
+    def serialize(self) -> bytes:
+        """Serialize the tree to UTF-8 JSON bytes."""
+        return json.dumps(self._entries).encode("utf-8")
+
+    def set_entry(self, name: str, uuid: str) -> None:
+        """Add or update an entry mapping name -> uuid."""
+        self._entries[name] = uuid
+
+    def rm_entry(self, name: str) -> None:
+        """Remove an entry by name. Raises KeyError if not found."""
+        del self._entries[name]
+
+    def list(self) -> dict[str, str]:
+        """Return a shallow copy of all entries as {name: uuid}."""
+        return dict(self._entries)