main.py

from dotenv import load_dotenv
load_dotenv() # Load env vars BEFORE importing anything else

from fastapi import FastAPI, Request, BackgroundTasks
from src.service import process_slack_event

app = FastAPI()

@app.post("/slack/message")
async def handle_slack_message(request: Request, background_tasks: BackgroundTasks):
    """
    Main Endpoint: Handles Verification, Deduplication, and Handoff.
    """
    # 1. IGNORE RETRIES
    # Slack retries requests if we take too long. We ignore them to prevent duplicate answers.
    if request.headers.get("x-slack-retry-num"):
        return {"status": "ignored"}

    # 2. PARSE JSON
    payload = await request.json()

    # 3. HANDLE VERIFICATION HANDSHAKE
    if payload.get("type") == "url_verification":
        return {"challenge": payload.get("challenge")}

    # 4. VALIDATE EVENT
    if "event" not in payload:
        return {"status": "ignored"}
    
    event = payload["event"]
    
    # 5. IGNORE BOTS (Prevent infinite loops)
    if "bot_id" in event:
        return {"status": "ignored"}

    # 6. QUEUE TASK & RETURN INSTANTLY
    # This prevents the Slack "3000ms timeout" error.
    background_tasks.add_task(process_slack_event, event)

    return {"status": "ok"}