"""
A simple self-correcting agent example using LangGraph.

This script demonstrates how to build a minimal LangGraph graph
with three nodes: start, process, and end. The graph concatenates
a greeting message and prints it at the end. The example ensures
that imports from `langgraph.graph` work correctly.
"""

from langgraph.graph import StateGraph, END
from typing import Dict, Any


class SimpleAgent:
    """
    A minimal agent that builds and runs a LangGraph graph.
    """

    def __init__(self) -> None:
        # Create a new StateGraph instance
        self.graph = StateGraph()

        # Add nodes to the graph
        self.graph.add_node("start", self.start_node)
        self.graph.add_node("process", self.process_node)
        self.graph.add_node("end", self.end_node)

        # Define the entry point and edges
        self.graph.set_entry_point("start")
        self.graph.add_edge("start", "process")
        self.graph.add_edge("process", "end")
        self.graph.add_edge("end", END)

    def start_node(self, state: Dict[str, Any]) -> Dict[str, Any]:
        """
        Initial node that sets the starting message.
        """
        state["message"] = "Hello"
        return state

    def process_node(self, state: Dict[str, Any]) -> Dict[str, Any]:
        """
        Process node that appends to the message.
        """
        state["message"] += " World"
        return state

    def end_node(self, state: Dict[str, Any]) -> Dict[str, Any]:
        """
        End node that prints the final message.
        """
        print(state["message"])
        return state

    def run(self) -> None:
        """
        Compile and execute the graph.
        """
        # Compile the graph into a runnable function
        runnable = self.graph.compile()

        # Execute the graph with an empty initial state
        runnable({})


if __name__ == "__main__":
    agent = SimpleAgent()
    agent.run()