no replica context

fiori/package.json

@@ -3,9 +3,10 @@
   "version": "1.0.0",
   "dependencies": {
     "@capire/bookshop": "*",
-    "@capire/reviews": "*",
-    "@capire/orders": "*",
     "@capire/common": "*",
+    "@capire/orders": "*",
+    "@capire/reviews": "*",
+    "@capire/suppliers": "*",
     "@sap/cds": "^4",
     "express": "^4.17.1",
     "passport": "^0.4.1"
@@ -19,6 +20,10 @@
       "deploy-format": "hdbtable"
     },
     "requires": {
+      "API_BUSINESS_PARTNER": {
+        "kind": "odata",
+        "model": "@capire/suppliers"
+      },
       "auth": {
         "strategy": "dummy"
       },

fiori/server.js

@@ -7,6 +7,7 @@ cds.once('bootstrap',(app)=>{
 })
 
 cds.once('served', require('./srv/mashup'))
+cds.once('served', require('@capire/suppliers/srv/mashup'))
 
 module.exports = cds.server
 

package.json

@@ -11,7 +11,8 @@
     "@capire/hello": "./hello",
     "@capire/media": "./media",
     "@capire/orders": "./orders",
-    "@capire/reviews": "./reviews"
+    "@capire/reviews": "./reviews",
+    "@capire/suppliers": "./suppliers"
   },
   "devDependencies": {
     "chai": "^4.2.0",
@@ -20,6 +21,7 @@
     "sqlite3": "5.0.0"
   },
   "scripts": {
+    "fix-antlr": "sed -i -e 's/INVALID_ALT_NUMBER = require.*/INVALID_ALT_NUMBER = 0/' node_modules/antlr4/tree/Trees.js node_modules/antlr4/RuleContext.js",
     "registry": "node .registry/server.js",
     "bookshop": "cds watch bookshop",
     "fiori": "cds watch fiori",

reviews/srv/reviews-service.cds

@@ -8,9 +8,9 @@ service ReviewsService {
   action unlike (review: type of Reviews:ID);
 
   // Async API
-   event reviewed : {
-     subject: type of Reviews:subject;
-     rating: Decimal(2,1)
+   event reviewed : projection on Reviews {
+     subject,
+     rating
    }
 
   // Input validation

samples.md

@@ -49,14 +49,22 @@ Each sub directory essentially is an individual npm package arranged in an [all-
 - Late-cut Micro Services
 - As well as managed data, input validations, and authorization
 
+## [@capire/suppliers](suppliers)
+
+- Shows how to integrate remote services, in this case the BusinessPartner service from SAP S/4HANA.
+- Extending [@capire/bookshop](bookshop) with suppliers from SAP S/4HANA
+- Providing that as a pre-built integration & extension package
+- Used in [@capire/fiori](fiori)
+
 
 ## [@capire/fiori](fiori)
 
 - A [composite app, reusing and combining](https://cap.cloud.sap/docs/guides/verticalize) these packages:
   - [@capire/bookshop](bookshop)
-  - [@capire/reviews](reviews)
-  - [@capire/orders](orders)
   - [@capire/common](common)
+  - [@capire/orders](orders)
+  - [@capire/reviews](reviews)
+  - [@capire/suppliers](suppliers)
 - [Adds an SAP Fiori elements application](https://cap.cloud.sap/docs/guides/fiori/) to bookshop, thereby introducing to:
   - [OData Annotations](https://cap.cloud.sap/docs/guides/fiori#adding-odata-annotations) in `.cds` files
   - Support for [Fiori Draft](https://cap.cloud.sap/docs/guides/fiori#draft)

suppliers/index.cds

@@ -0,0 +1 @@
+using from './srv/mashup';

suppliers/package.json

@@ -0,0 +1,24 @@
+{
+  "name": "@capire/suppliers",
+  "version": "1.0.0",
+  "description": "Shows integration with SAP S/4HANA, in turn provided as a reusable extension package to bookshop.",
+  "private": true,
+  "dependencies": {
+    "@capire/common": "*",
+    "@sap/cds": "^4",
+    "express": "^4"
+  },
+  "scripts": {
+    "start": "cds run --in-memory?",
+    "watch": "cds watch",
+    "mocked-s4": "cds mock API_BUSINESS_PARTNER"
+  },
+  "cds": {
+    "requires": {
+      "API_BUSINESS_PARTNER": {
+        "kind": "odata",
+        "model": "srv/external/API_BUSINESS_PARTNER"
+      }
+    }
+  }
+}

suppliers/server.js

@@ -0,0 +1,3 @@
+const cds = require ('@sap/cds')
+cds.once('served', require('./srv/mashup'))
+module.exports = cds.server

suppliers/srv/external/data/API_BUSINESS_PARTNER-A_BusinessPartner.csv

@@ -0,0 +1,7 @@
+BusinessPartner;BusinessPartnerFullName
+ACME;A Company Making Everything
+B4U;Books for You
+S&C;Shakespeare & Co.
+WSL;Waterstones
+TLD;Thalia
+PNG;Penguin Books

suppliers/srv/external/data/API_BUSINESS_PARTNER-Suppliers.csv

@@ -0,0 +1,5 @@
+ID;name
+ACME;A Company Making Everything
+B4U;Books for You
+S&C;Shakespeare & Co.
+WSL;Waterstones

suppliers/srv/mashup.cds

@@ -0,0 +1,25 @@
+/*
+  Optionally add projections to external entities, to capture what
+  you actually want to use from there.
+ */
+
+using {API_BUSINESS_PARTNER as S4} from './external/API_BUSINESS_PARTNER.csn';
+
+@cds.autoexpose // or expose explicitly in Catalog and AdminService
+@cds.persistence: {table,skip:false}
+entity sap.capire.bookshop.Suppliers as projection on S4.A_BusinessPartner {
+  key BusinessPartner as ID, BusinessPartnerFullName as name
+}
+
+using { sap.capire.bookshop.Books, CatalogService } from '@capire/bookshop';
+extend Books with {
+  supplier: Association to sap.capire.bookshop.Suppliers;
+}
+
+extend service AdminService with { // why is AdminService visible?
+  entity Suppliers as projection on sap.capire.bookshop.Suppliers;
+}
+
+extend projection CatalogService.ListOfBooks with {
+  supplier
+}

suppliers/srv/mashup.js

@@ -0,0 +1,57 @@
+////////////////////////////////////////////////////////////////////////////
+//
+//    Mashing up provided and required services...
+//
+module.exports = async()=>{ // called by server.js
+
+  if (!cds.services.AdminService) return //> mocking S4 service only
+
+  // Connect to services we want to mashup below...
+  const S4bupa = await cds.connect.to('API_BUSINESS_PARTNER')   //> external S4 service
+  const admin = await cds.connect.to('AdminService')            //> local domain service
+  const db = await cds.connect.to('db')                         //> our primary database
+
+  // Reflect CDS definition of the Suppliers entity
+  const { Suppliers } = S4bupa.entities
+
+  admin.prepend (()=>{ //> to ensure our .on handlers below go before the default ones
+
+    // Delegate Value Help reads for Suppliers to S4 backend
+    admin.on ('READ', 'Suppliers', req => {
+      console.log ('>> delegating to S4 service...')
+      return S4bupa.run(req.query)
+    })
+
+    // Replicate Supplier data when edited Books have suppliers
+    admin.on (['CREATE','UPDATE'], 'Books', ({data:{supplier}}, next) => {
+      // Using Promise.all(...) to parallelize local write, i.e. next(), and replication
+      if (supplier) return Promise.all ([ next(), async()=>{
+        let replicated = await db.exists (Suppliers, supplier)
+        if (!replicated) await replicate (supplier, 'initial')
+      }])
+      else return next() //> don't forget to pass down the interceptor stack
+    })
+
+  })
+
+  // Subscribe to changes in the S4 origin of Suppliers data
+  S4bupa.on ('BusinessPartners/Changed', async msg => { //> would be great if we had batch events from S/4
+    let replicas = await SELECT('ID').from (Suppliers) .where ('ID in', msg.businessPartners)
+    return replicate (replicas.map(each => each.ID))
+  })
+
+  /**
+   * Helper function to replicate Suppliers data.
+   * @param {string|string[]} IDs a single ID or an array of IDs
+   * @param {truthy|falsy} _initial indicates whether an insert or an update is required
+   */
+  async function replicate (IDs,_initial) {
+    if (!Array.isArray(IDs)) IDs = [ IDs ]
+    let suppliers = await S4bupa.read (Suppliers).where('ID in',IDs)
+    if (_initial) return db.insert (suppliers) .into (Suppliers) //> using bulk insert
+    else return Promise.all(suppliers.map ( //> parallelizing updates
+      each => db.update (Suppliers,each.ID) .with (each)
+    ))
+  }
+
+}