Play with db constraints

bookshop/srv/admin-service.cds

@@ -1,5 +1,6 @@
 using { sap.capire.bookshop as my } from '../db/schema';
-service AdminService @(requires:'admin') {
+service AdminService {
   entity Books as projection on my.Books;
   entity Authors as projection on my.Authors;
+  entity Genres as projection on my.Genres;
 }

bookshop/srv/admin-service.js

@@ -1,12 +1,15 @@
+// sqlite: FK constraint checks need to be enabled by application at runtime
+// for each db connection
 const cds = require('@sap/cds')
+module.exports = cds.service.impl (async function(){ 
 
-module.exports = cds.service.impl (function(){
-  this.before ('NEW','Authors', genid)
-  this.before ('NEW','Books', genid)
+  const db = await cds.connect.to('db')
+
+  if (db.kind === 'sqlite')
+  {
+    db.before('BEGIN', function (req) { 
+      //console.log('--- PRAGMA foreign_keys = ON ---')
+      return this.dbc.run('PRAGMA foreign_keys = ON;')
+    })
+  }
 })
-
-/** Generate primary keys for target entity in request */
-async function genid (req) {
-  const {ID} = await cds.tx(req).run (SELECT.one.from(req.target).columns('max(ID) as ID'))
-  req.data.ID = ID - ID % 100 + 100 + 1
-}

bookshop/srv/cat-service.cds

@@ -1,16 +0,0 @@
-using { sap.capire.bookshop as my } from '../db/schema';
-service CatalogService @(path:'/browse') {
-
-  /** For displaying lists of Books */
-  @readonly entity ListOfBooks as projection on Books
-  excluding { descr };
-
-  /** For display in details pages */
-  @readonly entity Books as projection on my.Books { *,
-    author.name as author
-  } excluding { createdBy, modifiedBy };
-
-  @requires: 'authenticated-user'
-  action submitOrder ( book: Books:ID, amount: Integer ) returns { stock: Integer };
-  event OrderedBook : { book: Books:ID; amount: Integer; buyer: String };
-}

bookshop/srv/cat-service.js

@@ -1,26 +0,0 @@
-const cds = require('@sap/cds')
-const { Books } = cds.entities ('sap.capire.bookshop')
-
-class CatalogService extends cds.ApplicationService { init(){
-
-  // Reduce stock of ordered books if available stock suffices
-  this.on ('submitOrder', async req => {
-    const {book,amount} = req.data
-    let {stock} = await SELECT `stock` .from (Books,book)
-    if (stock >= amount) {
-      await UPDATE (Books,book) .with (`stock -=`, amount)
-      await this.emit ('OrderedBook', { book, amount, buyer:req.user.id })
-      return { stock }
-    }
-    else return req.error (409,`${amount} exceeds stock for book #${book}`)
-  })
-
-  // Add some discount for overstocked books
-  this.after ('READ','ListOfBooks', each => {
-    if (each.stock > 111) each.title += ` -- 11% discount!`
-  })
-
-  return super.init()
-}}
-
-module.exports = { CatalogService }