from fastapi import APIRouter, HTTPException

users = []  # In-memory storage

router = APIRouter()

@router.get("/auth")
async def authenticate_user(
    username: str = "demo",
    password: str = "password"
):
    """authenticates the user with details"""
    if request.method != "GET":
        raise HTTPException(status_code=405, detail={
            "message": "Method Not Allowed",
            "method": request.method,
            "_verb": "get"
        })

    user = next((u for u in users if u["username"] == username), None)
    if not user or user["password"] != password:
        raise HTTPException(status_code=400, detail="Invalid credentials")

    return {
        "method": "GET", 
        "message": "Authentication successful (demo)",
        "user": username,
        "token": "dummy_jwt_token_123",
        "features": {
            "rate_limit": 100,
            "expires_in": 3600
        }
    }