"""
Main entry point for the Human‑in‑the‑loop LangGraph example.

The program demonstrates a simple graph with one node that pauses execution and asks the user to confirm an action.  The pause is implemented using ``langgraph``'s custom interrupt mechanism.  After the user answers, the graph resumes and prints the final state.

Requirements:
    pip install -r requirements.txt

Run:
    python main.py
"""

from __future__ import annotations

import os
from typing import Dict, Any

import questionary
from langgraph.constants import START
from langgraph.types import Command
from langgraph.checkpoint.memory import InMemorySaver
from graph import build_graph

# ---------------------------------------------------------------------------
# 1. Node that triggers an interrupt (defined in graph.py)
# ---------------------------------------------------------------------------
# The node is already defined in graph.py; we just use the compiled graph.

# ---------------------------------------------------------------------------
# Main loop that runs the graph and handles interrupts
# ---------------------------------------------------------------------------
async def run_graph() -> None:
    """Execute the graph, handle the custom interrupt, and resume execution."""
    from asyncio import run  # Imported lazily to keep top‑level imports minimal.

    graph = build_graph()
    config = {"configurable": {"thread_id": "demo-thread-1"}}

    # Initial state – ``foo`` can be any value; it is not used in this demo.
    init_state: Dict[str, Any] = {"human_value": None, "foo": 42}

    async for chunk in graph.stream(init_state, config):
        if "__interrupt__" in chunk:
            interrupt_obj = chunk["__interrupt__"][0]
            payload: Dict[str, Any] = interrupt_obj.value  # type: ignore[assignment]

            print("\n--- Human‑in‑the‑loop interrupt received ---")
            print(f"Type: {payload.get('type')}")
            print(f"Question: {payload.get('question')}\n")

            # Ask the user for a choice.
            answer = questionary.select(
                "Choose an option:",
                choices=payload.get("options", []),
            ).ask()

            if answer is None:
                raise RuntimeError("User cancelled the prompt")

            # Attach the answer to the payload and resume.
            payload["answer"] = answer
            print(f"\n> User selected: {answer}\n")
            await graph.stream(Command(resume=payload), config)
        else:
            # Normal output – just print it.
            if "messages" in chunk:
                for msg in chunk["messages"]:
                    print(msg.content, end="", flush=True)

    # After the stream ends, fetch the final state from the checkpoint.
    final_state = graph.checkpointer.get_state(config)
    print("\n--- Final state ---")
    print(final_state)

# ---------------------------------------------------------------------------
# Entry point
# ---------------------------------------------------------------------------
if __name__ == "__main__":
    import asyncio

    try:
        asyncio.run(run_graph())
    except KeyboardInterrupt:
        print("\nInterrupted by user.")