# Human‑in‑the‑loop (Interrupt / Resume) – LangGraph Demo

This repository contains a minimal example of a **LangGraph** that pauses execution to ask the user for confirmation via a custom interrupt.  
The graph demonstrates how to:

* Define a typed state with fields that will be filled by a human.
* Trigger an interrupt from a node, passing a structured payload (`type`, `question`, `allow_responds`).
* Handle the interrupt in a loop: display the question in the console (using *questionary*), capture the answer and resume the graph.

---

## 📦 Installation

```bash
# Create a virtual environment if you wish
python -m venv .venv
source .venv/bin/activate   # On Windows use `.venv\Scripts\activate`

# Install dependencies
pip install langgraph questionary
```

> **Tip**: If you plan to extend the graph with LLM calls, add `langchain` and an appropriate provider (e.g., `langchain-openai`) to your requirements.

---

## 📁 Project Structure

```text
.
├── interrupt_graph.py   # The LangGraph implementation
└── README.md            # This file
```

---

## 🚀 Running the Example

The graph is executed in a simple loop that keeps running until the user chooses to stop.  
Run it with:

```bash
python interrupt_graph.py
```

You should see something like:

```
[Graph] Starting new run...
[Interrupt] type: confirm
Question: Уверены, что хотите продолжить?
Options: approve / reject

Your choice: approve
[Graph] Resuming after interrupt...

[Graph] Run finished. Final state:
{'human_value': 'approve', 'foo': None}
```

If you answer `reject`, the graph will still resume but with a different value.

---

## 📄 Example Usage in Code

```python
# interrupt_graph.py (excerpt)

from langgraph.types import interrupt

def node_with_interrupt(state: GraphState) -> GraphState:
    if state.get("human_value") is not None:
        return state

    payload = {
        "type": "confirm",
        "question": "Уверены, что хотите продолжить?",
        "allow_responds": ["approve", "reject"],
    }
    # Pause the graph until a human responds
    return interrupt(payload)
```

The main loop in `interrupt_graph.py` handles this payload:

```python
while True:
    result = graph.run(state=state, config=config)
    if isinstance(result, Command):
        # Show question and get answer
        choice = questionary.select(
            result.payload["question"],
            choices=result.payload["allow_responds"]
        ).ask()
        state["human_value"] = choice
        continue  # resume graph
    else:
        break  # finished
```

---

## 🎯 What You Can Learn

* How to **pause** a LangGraph node and wait for user input.
* How to structure the interrupt payload so that it can be rendered in any UI (console, web, etc.).
* The pattern of looping over `graph.run()` until no more `Command` objects are returned.

Feel free to fork this repository and experiment with different interrupt types or add LLM calls to make the graph more complex!