main.js

// Session.setDefault('sidebar-view-state', null);
// Session.setDefault('sidebar-drawer-state', null);
// Session.setDefault('sidebar-sub-drawer-state', null);

Carts = new Meteor.Collection('carts');
Products = new Meteor.Collection('products');
Payments = new Meteor.Collection('payments');

Meteor.methods({ });

if (Meteor.isClient) {
  Carts.create = function() {
    return Carts.insert({
      productIds: [],
      paymentIds: [],
    });
  }

  _.extend(Template.cart, {
    created: function() {
      Meteor.subscribe('cart', 'jXSPZhyxRxsvnKjMv');
    },

    products: function() {
      var cart = Carts.findOne();
      if (!cart) {
        return;
      }
      return Products.find({ _id: { $in: cart.productIds }});
    },

    payments: function() {
      var cart = Carts.findOne();
      if (!cart) {
        return;
      }
      return Payments.find({ _id: { $in: cart.paymentIds }});
    }
  });

  _.extend(Template.products, {
    created: function() {
      Meteor.subscribe('products');
    },

    products: function() {
      return Products.find();
    }
  });
}

if (Meteor.isServer) {
  Meteor.publish('products', function() {
    return Products.find();
  });

  Meteor.publish('cart', function(id) {
    Meteor.publishWithRelations({
      handle: this,
      collection: Carts,
      filter: id,
      mappings: [{
        key: 'productIds',
        collection: Products
      }, {
        key: 'paymentIds',
        collection: Payments
      }]
    });
  });

  Meteor.startup(function () {
    if (Products.find().count() === 0) {
      console.log("Add Products");

      var bookId = Products.insert({
        name: "George Barbier",
        price: 24.00
      });

      var coffeeId = Products.insert({
        name: "Flat White",
        price: 1.30
      });

      var printId = Products.insert({
        name: "Espresso Screen Print",
        price: 24.00
      });
    }

    if (Payments.find().count() === 0) {
      console.log("Add payment");

      var paymentId = Payments.insert({
        method: "cash",
        value: 2.33
      });
    }

    if (Carts.find().count() === 0) {
      console.log("Create cart");

      var cartId = Carts.insert({
        productIds: [bookId, printId],
        paymentIds: [paymentId]
      });
    }
  });
}