main.py

from fastapi import FastAPI, HTTPException
from pydantic import BaseModel
from langchain_core.messages import HumanMessage, AIMessage
from agent import chat_graph
import uvicorn

# FastAPI Implementation
app = FastAPI(title="ChatGPT Clone Backend")

class ChatRequest(BaseModel):
    message: str
    thread_id: str

class ChatResponse(BaseModel):
    response: str

@app.post("/chat", response_model=ChatResponse)
async def chat_endpoint(request: ChatRequest):
    config = {"configurable": {"thread_id": request.thread_id}}
    
    try:
        # Run the graph
        initial_input = {"messages": [HumanMessage(content=request.message)]}
        result = chat_graph.invoke(initial_input, config=config)
        
        # Get the last AI message from the conversation history
        last_message = None
        for msg in reversed(result["messages"]):
            if isinstance(msg, AIMessage):
                last_message = msg
                break
        
        if last_message:
            return ChatResponse(response=last_message.content)
        else:
            return ChatResponse(response="I have processed your request but couldn't generate a final response. Please try rephrasing.")
            
    except Exception as e:
        print(f"Error in chat endpoint: {e}")
        raise HTTPException(status_code=500, detail=str(e))

if __name__ == "__main__":
    print("Starting ChatGPT Clone API Server...")
    print("API Documentation: http://localhost:8000/docs")
    print("API will be available at: http://localhost:8000")
    
    uvicorn.run("main:app", host="0.0.0.0", port=8000, reload=True)