cleaned up

bookshop/srv/admin-service.cds

@@ -3,5 +3,4 @@ using { sap.capire.bookshop as my } from '../db/schema';
 service AdminService @(_requires:'authenticated-user') {
   entity Books as projection on my.Books;
   entity Authors as projection on my.Authors;
-  entity Orders as select from my.Orders;
 }

bookshop/srv/cat-service.cds

@@ -1,13 +1,12 @@
 using { sap.capire.bookshop as my } from '../db/schema';
 
-@path:'/browse'
-service CatalogService {
+service CatalogService @(path:'/browse') {
 
   @readonly entity Books as SELECT from my.Books {*,
     author.name as author
   } excluding { createdBy, modifiedBy };
 
   @requires_: 'authenticated-user'
-  @insertonly entity Orders as projection on my.Orders;
+  action order (book : Books.ID, amount: Integer);
 
 }

bookshop/srv/cat-service.js

@@ -1,26 +1,23 @@
 const cds = require('@sap/cds')
-const { Books } = cds.entities
 
 /** Service implementation for CatalogService */
-module.exports = cds.service.impl(function() {
-  this.after ('READ', 'Books', each => each.stock > 111 && _addDiscount2(each,11))
-  this.before ('CREATE', 'Orders', _reduceStock)
+module.exports = cds.service.impl (function() {
+
+  // Get entity definitions from reflected model
+  const { Books } = cds.entities
+
+  // Add some discount for overstocked books
+  this.after ('READ', 'Books', each => {
+    if (each.stock > 111)  each.title += ` -- 11% discount!`
+  })
+
+  // Reduce stock of ordered books if available stock suffices
+  this.on ('order', async (req) => {
+    const {UPDATE} = cds.ql(req), {book,amount} = req.data
+    const n = await UPDATE (Books, book)
+      .where ('stock >=', amount)
+      .set ('stock -=', amount)
+    n > 0 || req.error (409,`${amount} exceeds stock for book #${book}`)
+  })
+
 })
-
-/** Add some discount for overstocked books */
-function _addDiscount2 (each,discount) {
-  each.title += ` -- ${discount}% discount!`
-}
-
-/** Reduce stock of ordered books if available stock suffices */
-async function _reduceStock (req) {
-  const { Items: OrderItems } = req.data
-  return cds.transaction(req) .run (()=> OrderItems.map (order =>
-    UPDATE (Books) .set ('stock -=', order.amount)
-    .where ('ID =', order.book_ID) .and ('stock >=', order.amount)
-  )) .then (all => all.forEach ((affectedRows,i) => {
-    if (affectedRows === 0)  req.error (409,
-      `${OrderItems[i].amount} exceeds stock for book #${OrderItems[i].book_ID}`
-    )
-  }))
-}