models/stockSubscriptionModel.js

const mongoose = require('mongoose');

const stockSubscriptionSchema = new mongoose.Schema(
  {
    user: {
      type: mongoose.Schema.Types.ObjectId,
      ref: 'User',
      required: [true, 'Subscription must belong to a user'],
      index: true,
    },
    product: {
      type: mongoose.Schema.Types.ObjectId,
      ref: 'Product',
      required: [true, 'Subscription must reference a product'],
      index: true,
    },
    notifiedAt: {
      type: Date,
      default: null,
      // Set when the user has been notified; null means still waiting
    },
  },
  {
    timestamps: true,
  },
);

// Prevent duplicate subscriptions per user+product
stockSubscriptionSchema.index({ user: 1, product: 1 }, { unique: true });

const StockSubscription = mongoose.model(
  'StockSubscription',
  stockSubscriptionSchema,
);

module.exports = StockSubscription;