First push

bookshop/srv/admin-service.cds

@@ -1,5 +1,13 @@
-using { sap.capire.bookshop as my } from '../db/schema';
-service AdminService @(requires:'admin') {
-  entity Books as projection on my.Books;
+using {sap.capire.bookshop as my} from '../db/schema';
+
+service AdminService // @(requires : 'admin')
+{
+  entity Books   as projection on my.Books;
   entity Authors as projection on my.Authors;
+  action renameAuthor(author : Authors:ID, newName : String);
+
+  event newBook : {
+    book : Books:ID;
+    name : Books:title
+  };
 }

bookshop/srv/admin-service.js

@@ -1,77 +1,144 @@
-const cds = require("@sap/cds");
-const { VM, VMScript } = require("vm2");
-const fs = require("fs");
-const path = require("path");
+const cds = require("@sap/cds")
+const cds_sandbox = require("sap/cds/sandbox")
+const { VM, VMScript } = require("vm2")
+const fs = require("fs")
+const path = require("path")
+const { nextTick } = require("process")
 
 class AdminService extends cds.ApplicationService {
   init() {
-    const { Books, Authors } = cds.entities("sap.capire.bookshop");
-
     this.after("READ", async (result, req) => {
-      const code = getCode(req, "READ");
-      if (code) {
-        await executeCode(code, req, result);
+      if (!(result === undefined || result == null)) {
+        const code = getCode(req.target.name, "READ")
+        if (code) {
+          await executeCode(code, req, result)
+        }
       }
-    });
-
-    this.after("READ", "ListOfBooks", (each) => {
-      if (each.stock > 111) each.title += ` -- 11% discount!`;
-    });
+    })
 
     this.before("CREATE", async (req) => {
-      const code = getCode(req, "CREATE");
+      const code = getCode(req.target.name, "CREATE")
       if (code) {
-        await executeCode(code, req);
-        //console.log(req.data)
+        await executeCode(code, req)
       }
-    });
+    })
 
-    //this.before("NEW", "Authors", genid);
-    //this.before("NEW", "Books", genid);
-    return super.init();
+    this.before("UPDATE", async (req) => {
+      const code = getCode(req.target.name, "CREATE")
+      if (code) {
+        await executeCode(code, req)
+      }
+    })
+
+    this.on("*", async (req, next) => {
+      if (!(req.target === undefined || req.target == null)) return next()
+      //ToDo: check whether action or event is part of an extension
+      if (req.constructor.name === "EventMessage") {
+        const code = getCode(req.event, "ON")
+        if (code) {
+          await executeCode(code, req)
+        }
+      } else if (req.constructor.name === "ODataRequest") {
+        var output = {}
+        const code = getCode(this.name + "." + req.event, "ON")
+        if (code) {
+          await executeCode(code, req, {}, output)
+          return output
+        }
+      }
+    })
+
+    //ToDo: Prefix for Service not in event emitter
+    this.before("CREATE", "Authors", async (req) => {
+      let Author = req.data
+      await this.emit("createdAuthor", { Author })
+
+    })
+ 
+    return super.init()
   }
 }
 
-function getCode(req, operation) {
-  const filename = req.target.name + "." + operation + ".js";
-  const file = path.join(__dirname, "..", "handlers", filename);
+var counter = 1;
+
+function newLabel() {return "VM2 - req: " + counter++}
+
+function getCode(name, operation) {
+  const filename = name + "." + operation + ".js"
+  const file = path.join(__dirname, "..", "handlers", filename)
   try {
-    const code = fs.readFileSync(file, "utf8");
-    return code;
+    const code = fs.readFileSync(file, "utf8")
+    return code
   } catch (error) {
-    return "";
+    return ""
   }
 }
 
 function scanCode(code) {
   //ESLINT
 }
+/*
+Base assumption: event handlers will always use publicly available application API's (services)
+Inbound data for validations
+  - this could be a document --> req.target plus expand on related data
+  - event facade could have an explicit publishing of specific services or documents (e.g. remote services)
+  - CQN Protocol adapter for subsequent reads --> req.data plus application service calls
+  - what is the CDS subset to put in?
+    - req.data + target-rec (proxy, unloaded)
+    - ORM type lazy loading (dereferenced)
+    - application developer could actually provide custom proxies for specific functions
+    - performance impact of multiple accesses to object graph and multiple DB roundtrips
+    - can static code checking or developer annotations influence what is loaded into a graph?
+    - alternative: Stripped-down SELECT limited to req.target and ID
+      - application service only
+      - access rights of user respected
+  - What about to-many relationships? For compositions essential, for associations to be questioned
+  - Application Service Reads
+  - outbound data for changes
+  - call remote services
+    - register new remote services dynamically
+    - CAP provides an API on remote services - connect doesn't need to be done by extension developer
+    - alternative: declarative remote services plumbing with CDS service facade
+      - model looks like static internal services, remote calls done transparently behind the scenes
 
-async function executeCode(code, req, result) {
-  let output = {};
-  console.time("vm2");
+  -Emit Events
+    
+  - choreography of extension points
+    - deep inserts vs. fine grained operations
+    - input validation may be suited for fine grained operations
+    - today not in scope for performance reasons
+    - two different use case: Insert new page to book vs. update order-header with items-constraints in place
+  - reject request, return errors and warnings - suitable for UI, too
+
+*/
+async function executeCode(code, req, result, output) {
+  const label=newLabel()
+  console.time(label)
   const vm = new VM({
     console: "inherit",
-    timeout: 1000,
+    timeout: 500,
     allowAsync: true,
     sandbox: { req, result, output, cds, SELECT, INSERT, UPDATE, CREATE, JSON },
-  });
-  
+  })
+
   try {
     await vm.run(code)
+    return output
   } catch (error) {
-    req.reject('409','Error in VM')
     console.log(error)
+    req.reject("409", "Error in VM")
+  }
+  finally {
+    console.timeEnd(label)
   }
   // console.log(req.data)
-  console.timeEnd("vm2");
 }
 /** 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;
+    .run(SELECT.one.from(req.target).columns("max(ID) as ID"))
+  req.data.ID = ID - (ID % 100) + 100 + 1
 }
 
-module.exports = { AdminService };
+module.exports = { AdminService }