"""
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


from .trove import ObjectId


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 not data:
            self._entries: dict[str, ObjectId] = {}
        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, object_id: ObjectId) -> None:
        """Add or update an entry mapping name -> uuid."""
        self._entries[name] = object_id

    def get_entry(self, name: str) -> ObjectId:
        """Get the uuid associated with a name, or raise KeyError if not found."""
        return self._entries[name]

    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, ObjectId]:
        """Return a shallow copy of all entries as {name: uuid}."""
        return dict(self._entries)