utils/sendPush.js

const webpush = require('web-push');
const User = require('../models/User');

// Configure Keys (Ensure these are in your .env)
webpush.setVapidDetails(
  process.env.VAPID_EMAIL,
  process.env.VAPID_PUBLIC_KEY,
  process.env.VAPID_PRIVATE_KEY
);

// SEND TO ONE USER
const sendToUser = async (userId, title, message, url = '/') => {
  try {
    const user = await User.findById(userId);
    if (user && user.pushSubscription) {
      await webpush.sendNotification(
        user.pushSubscription, 
        JSON.stringify({ title, body: message, url })
      );
    }
  } catch (err) {
    // 410 = Gone (User unsubscribed/cleared cache)
    if (err.statusCode === 410) {
       await User.findByIdAndUpdate(userId, { $unset: { pushSubscription: "" } });
    }
    console.error("Push Error (Single):", err.statusCode);
  }
};

// SEND TO EVERYONE (Batching for performance)
const sendGlobal = async (title, message, url = '/') => {
  try {
    // Fetch users who have a subscription
    const users = await User.find({ pushSubscription: { $exists: true } });
    const payload = JSON.stringify({ title, body: message, url });

    console.log(`📢 Sending Global Push to ${users.length} devices...`);

    const promises = users.map(user => 
      webpush.sendNotification(user.pushSubscription, payload).catch(err => {
         if (err.statusCode === 410) {
           User.findByIdAndUpdate(user._id, { $unset: { pushSubscription: "" } });
         }
      })
    );

    await Promise.all(promises);
  } catch (err) {
    console.error("Push Error (Global):", err);
  }
};

module.exports = { sendToUser, sendGlobal };