"""Agent types with async initialization and dynamic graph creation."""

from abc import ABC, abstractmethod

from langgraph.graph.state import CompiledStateGraph
from langgraph.pregel import Pregel


class LazyLoadingAgent(ABC):
    """Base class for agents that require async loading."""

    def __init__(self) -> None:
        """Initialize the agent."""
        self._loaded = False
        self._graph: CompiledStateGraph | Pregel | None = None

    @abstractmethod
    async def load(self) -> None:
        """
        Perform async loading for this agent.

        This method is called during service startup and should handle:
        - Setting up external connections (MCP clients, databases, etc.)
        - Loading tools or resources
        - Any other async setup required
        - Creating the agent's graph
        """
        raise NotImplementedError  # pragma: no cover

    def get_graph(self) -> CompiledStateGraph | Pregel:
        """
        Get the agent's graph.

        Returns the graph instance that was created during load().

        Returns:
            The agent's graph (CompiledStateGraph or Pregel)
        """
        if not self._loaded:
            raise RuntimeError("Agent not loaded. Call load() first.")
        if self._graph is None:
            raise RuntimeError("Agent graph not created during load().")
        return self._graph