# main.py

from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from uuid import uuid4

from models import InitChatRequest, ChatRequest, EndSessionRequest
from rag_chain import build_chain

app = FastAPI()

# CORS setup
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# In-memory session storage
chat_sessions = {}

@app.get("/")
def root():
    return {"message": "API is running"}

@app.post("/init")
def initialize_chat(req: InitChatRequest):
    try:
        session_id = str(uuid4())
        qa_chain = build_chain(req.video_id)
        chat_sessions[session_id] = qa_chain
        return {"message": "Chat session started", "session_id": session_id}
    except Exception as e:
        raise HTTPException(status_code=500, detail=str(e))


@app.post("/chat")
def chat(req: ChatRequest):
    session_id = req.session_id
    if session_id not in chat_sessions:
        raise HTTPException(status_code=404, detail="Invalid session ID. Initialize session first.")
    
    try:
        qa_chain = chat_sessions[session_id]
        result = qa_chain.invoke({"query": req.query})

        return {
            "answer": result["result"],
            "sources": [doc.page_content for doc in result["source_documents"]]
        }
    except Exception as e:
        raise HTTPException(status_code=500, detail=str(e))


@app.post("/end")
def end_chat_session(req: EndSessionRequest):
    session_id = req.session_id
    if session_id in chat_sessions:
        del chat_sessions[session_id]
        return {"message": f"Session {session_id} ended successfully."}
    else:
        raise HTTPException(status_code=404, detail="Session ID not found.")