Adopt repository structure

srv/admin-service.cds

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+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;
+}
+
+// Enable Fiori Draft for Orders
+annotate AdminService.Orders with @odata.draft.enabled;
+// annotate AdminService.Books with @odata.draft.enabled;
+
+// Temporary workaround -> https://github.wdf.sap.corp/cap/issues/issues/3121
+extend service AdminService with {
+  entity OrderItems as select from my.OrderItems;
+}

srv/cat-service.cds

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+using { sap.capire.bookshop as my } from '../db/schema';
+
+@path:'/browse'
+service CatalogService {
+
+  @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;
+
+}

srv/cat-service.js

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+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)
+})
+
+/** 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}`
+    )
+  }))
+}