import uuid
import time
from django.core.cache import cache

QR_TOKEN_PREFIX = "qr_token:"
QR_TOKEN_EXPIRE = 300
QR_CONFIRM_EXPIRE = 120


def generate_qr_token():
    token = uuid.uuid4().hex
    key = f"{QR_TOKEN_PREFIX}{token}"
    cache.set(key, {
        "status": "waiting",
        "user_id": None,
        "scan_user_id": None,
        "scan_username": None,
        "created_at": time.time(),
        "expires_at": time.time() + QR_TOKEN_EXPIRE,
    }, QR_TOKEN_EXPIRE)
    return token


def get_qr_status(token):
    key = f"{QR_TOKEN_PREFIX}{token}"
    data = cache.get(key)
    if not data:
        return {"status": "expired"}
    return data


def scan_qr(token, user_id, username):
    key = f"{QR_TOKEN_PREFIX}{token}"
    data = cache.get(key)
    if not data or data["status"] != "waiting":
        return False
    data["status"] = "scanned"
    data["scan_user_id"] = user_id
    data["scan_username"] = username
    data["expires_at"] = time.time() + QR_CONFIRM_EXPIRE
    cache.set(key, data, QR_CONFIRM_EXPIRE)
    return True


def confirm_qr(token):
    key = f"{QR_TOKEN_PREFIX}{token}"
    data = cache.get(key)
    if not data or data["status"] != "scanned":
        return None
    data["status"] = "confirmed"
    cache.set(key, data, 60)
    return data


def cancel_qr(token):
    key = f"{QR_TOKEN_PREFIX}{token}"
    data = cache.get(key)
    if data:
        data["status"] = "cancelled"
        cache.set(key, data, 60)