"""Visitor state tracking for the Matrix frontend.

Tracks active visitors as they connect and move around the 3D world,
and provides serialization for Matrix protocol broadcast messages.
"""

import time
from dataclasses import dataclass, field
from datetime import UTC, datetime


@dataclass
class VisitorState:
    """State for a single visitor in the Matrix.

    Attributes
    ----------
    visitor_id: Unique identifier for the visitor (client ID).
    display_name: Human-readable name shown above the visitor.
    position: 3D coordinates (x, y, z) in the world.
    rotation: Rotation angle in degrees (0-360).
    connected_at: ISO timestamp when the visitor connected.
    """

    visitor_id: str
    display_name: str = ""
    position: dict[str, float] = field(default_factory=lambda: {"x": 0.0, "y": 0.0, "z": 0.0})
    rotation: float = 0.0
    connected_at: str = field(
        default_factory=lambda: datetime.now(UTC).strftime("%Y-%m-%dT%H:%M:%SZ")
    )

    def __post_init__(self):
        """Set display_name to visitor_id if not provided; copy position dict."""
        if not self.display_name:
            self.display_name = self.visitor_id
        # Copy position to avoid shared mutable state
        self.position = dict(self.position)


class VisitorRegistry:
    """Registry of active visitors in the Matrix.

    Thread-safe singleton pattern (Python GIL protects dict operations).
    Used by the WebSocket layer to track and broadcast visitor positions.
    """

    _instance: "VisitorRegistry | None" = None

    def __new__(cls) -> "VisitorRegistry":
        """Singleton constructor."""
        if cls._instance is None:
            cls._instance = super().__new__(cls)
            cls._instance._visitors: dict[str, VisitorState] = {}
        return cls._instance

    def add(
        self, visitor_id: str, display_name: str = "", position: dict | None = None
    ) -> VisitorState:
        """Add a new visitor to the registry.

        Parameters
        ----------
        visitor_id: Unique identifier for the visitor.
        display_name: Optional display name (defaults to visitor_id).
        position: Optional initial position (defaults to origin).

        Returns
        -------
        The newly created VisitorState.
        """
        visitor = VisitorState(
            visitor_id=visitor_id,
            display_name=display_name,
            position=position if position else {"x": 0.0, "y": 0.0, "z": 0.0},
        )
        self._visitors[visitor_id] = visitor
        return visitor

    def remove(self, visitor_id: str) -> bool:
        """Remove a visitor from the registry.

        Parameters
        ----------
        visitor_id: The visitor to remove.

        Returns
        -------
        True if the visitor was found and removed, False otherwise.
        """
        if visitor_id in self._visitors:
            del self._visitors[visitor_id]
            return True
        return False

    def update_position(
        self,
        visitor_id: str,
        position: dict[str, float],
        rotation: float | None = None,
    ) -> bool:
        """Update a visitor's position and rotation.

        Parameters
        ----------
        visitor_id: The visitor to update.
        position: New 3D coordinates (x, y, z).
        rotation: Optional new rotation angle.

        Returns
        -------
        True if the visitor was found and updated, False otherwise.
        """
        if visitor_id not in self._visitors:
            return False

        self._visitors[visitor_id].position = position
        if rotation is not None:
            self._visitors[visitor_id].rotation = rotation
        return True

    def get(self, visitor_id: str) -> VisitorState | None:
        """Get a single visitor's state.

        Parameters
        ----------
        visitor_id: The visitor to retrieve.

        Returns
        -------
        The VisitorState if found, None otherwise.
        """
        return self._visitors.get(visitor_id)

    def get_all(self) -> list[dict]:
        """Get all active visitors as Matrix protocol message dicts.

        Returns
        -------
        List of visitor_state dicts ready for WebSocket broadcast.
        Each dict has: type, visitor_id, data (with display_name,
        position, rotation, connected_at), and ts.
        """
        now = int(time.time())
        return [
            {
                "type": "visitor_state",
                "visitor_id": v.visitor_id,
                "data": {
                    "display_name": v.display_name,
                    "position": v.position,
                    "rotation": v.rotation,
                    "connected_at": v.connected_at,
                },
                "ts": now,
            }
            for v in self._visitors.values()
        ]

    def clear(self) -> None:
        """Remove all visitors (useful for testing)."""
        self._visitors.clear()

    def __len__(self) -> int:
        """Return the number of active visitors."""
        return len(self._visitors)