product.js

// api/product/services/product.js
"use strict";

const { createCoreService } = require("@strapi/strapi").factories;

module.exports = createCoreService("api::product.product", ({ strapi }) => ({
  async handleTransactionUpdate(event) {
    const { result } = event;
    strapi.log.info(
      `Acting upon an updated transaction - id: ${result.id}, status: ${result.status}`
    );
    if (result.status === "COMPLETED") {
      const productCollection = await strapi.query("api::product.product");
      // Collect all products mentioned in the transaction
      const productIds = result.products.map((product) => product.id);
      const productsList = await productCollection.findMany({
        id: { in_: productIds },
      });
      // Translate the list of products into a map with product uids as keys
      const products = {};
      for (let i = 0; i < productsList.length; i++) {
        products[productsList[i].id] = productsList[i];
      }
      // Update the products inventory
      const promises = [];
      for (const idx in result.products) {
        const boughtProduct = result.products[idx];
        const product = products[boughtProduct.id];
        promises.push(
          productCollection.update({
            where: { id: product.id },
            data: { inventory: product.inventory - boughtProduct.quantity },
          })
        );
      }
      // Finish after all promises are resolved
      await Promise.all(promises);
    }
  },
}));