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graphql/db/schema.cds

@@ -1,4 +1,7 @@
-using {managed} from '@sap/cds/common';
+using {
+  cuid,
+  managed
+} from '@sap/cds/common';
 using {sap.capire.bookshop} from '@capire/bookshop';
 
 namespace sap.capire.graphql;
@@ -13,3 +16,11 @@ entity Chapters : managed {
   key number : Integer;
       title  : String;
 }
+
+entity Orders : cuid, managed {
+  @mandatory
+  book     : Association to bookshop.Books;
+  @mandatory
+  @assert.range : [ 1, 5 ]
+  quantity : Integer;
+}

graphql/examples.http

@@ -1 +1,7 @@
-GET http://localhost:4007/graphql?query={AdminService{Books{title,chapters{number,title}}}}
+# GraphQL
+GET http://localhost:4007/graphql?query={BookshopService{Books{title,author{name},chapters{number,title}}}}
+
+###
+
+# OData
+GET http://localhost:4007/bookshop/Books?$select=title&$expand=author($select=name),chapters($select=number,title)

graphql/examples.md

@@ -2,7 +2,7 @@
 2. paste into left field:
     ```graphql
     {
-      AdminService {
+      BookshopService {
         Books {
           title
           chapters {

graphql/server.js

@@ -0,0 +1,20 @@
+const cds = require('@sap/cds')
+
+// redeploy the db incl. initial data for demo purposes
+cds.on('bootstrap', app => {
+  app.post('/redeploy', async (req, res) => {
+    await cds.deploy('*')
+    res.status(204).end()
+  })
+})
+
+// fix cds.context not being set correctly in GraphQL adapter
+cds.on('serving', srv => {
+  const { dispatch } = srv
+  srv.dispatch = function(req) {
+    if (!(cds.context instanceof cds.Request)) cds.context = this
+    return dispatch.call(this, req)
+  }
+})
+
+module.exports = cds.server

graphql/srv/admin-service.cds

@@ -1,5 +0,0 @@
-using {sap.capire.graphql} from '../db/schema';
-
-extend service AdminService with {
-  entity Chapters as projection on graphql.Chapters;
-}

graphql/srv/bookshop-service.cds

@@ -0,0 +1,11 @@
+using {
+  sap.capire.bookshop,
+  sap.capire.graphql
+} from '../db/schema';
+
+service BookshopService {
+  entity Books    as projection on bookshop.Books;
+  entity Authors  as projection on bookshop.Authors;
+  entity Chapters as projection on graphql.Chapters;
+  entity Orders   as projection on graphql.Orders;
+}

graphql/srv/bookshop-service.js

@@ -0,0 +1,11 @@
+module.exports = function() {
+  const { Orders, Books } = this.entities
+
+  this.before('CREATE', Orders, async function(req) {
+    const { book_ID, quantity } = req.data
+
+    // reduce the stock, if enough are available, else reject the order
+    const applied = await UPDATE(Books, book_ID).set({ stock: { '-=': quantity } }).where({ stock: { '>=': quantity }})
+    if (!applied) req.reject(400, `Sorry, ${quantity} are not in stock`)
+  })
+}