86 lines
3.2 KiB
JavaScript
86 lines
3.2 KiB
JavaScript
////////////////////////////////////////////////////////////////////////////
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//
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// Mashing up provided and required services...
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//
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module.exports = async()=>{ // called by server.js
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if (!cds.services.AdminService) return //> mocking S4 service only
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// Connect to services we want to mashup below...
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const S4bupa = await cds.connect.to('API_BUSINESS_PARTNER') //> external S4 service
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const admin = await cds.connect.to('AdminService') //> local domain service
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const db = await cds.connect.to('db') //> our primary database
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// Reflect CDS definition of the Suppliers entity
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const Suppliers = db.entities["sap.capire.bookshop.Suppliers"];
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admin.prepend (()=>{ //> to ensure our .on handlers below go before the default ones
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// Delegate Value Help reads for Suppliers to S4 backend
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admin.on ('READ', 'Suppliers', req => {
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console.log ('>> delegating to S4 service...')
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return S4bupa.run(req.query)
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})
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// Replicate Supplier data when edited Books have suppliers
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admin.on (['CREATE','UPDATE'], 'Books', async ({data:{supplier_ID: supplierId}}, next) => {
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// Using Promise.all(...) to parallelize local write, i.e. next(), and replication
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const replicateIfNotExists = async()=>{
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let replicated = await db.exists (Suppliers, supplierId);
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if (!replicated) await replicate (supplierId, 'initial');
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};
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if (supplierId) return Promise.all ([ next(), replicateIfNotExists() ])
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else return next() //> don't forget to pass down the interceptor stack
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})
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})
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// Subscribe to changes in the S4 origin of Suppliers data
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S4bupa.on ('BusinessPartner.Changed', async msg => { //> would be great if we had batch events from S/4
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console.log(">>", msg.event)
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const id = msg.data.BusinessPartner;
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let replica = await SELECT.one('ID').from (Suppliers) .where ('ID =', id);
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if (replica) await replicate(id);
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})
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/**
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* Helper function to replicate Suppliers data.
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* @param {string} a single ID
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* @param {truthy|falsy} _initial indicates whether an insert or an update is required
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*/
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async function replicate (id,_initial) {
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// TODO: Doesn't work when running in same process with mocked API_BUSINESS_PARTNER
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// TODO: Doesn't work because fields are not mapped back!
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//let supplier = await S4bupa.run(SELECT.one('*').from(Suppliers).where('ID =',id));
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let suppliers = await S4bupa.read(Suppliers).where('ID =',id);
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if (_initial) return db.insert (suppliers) .into (Suppliers) //> using bulk insert
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else return db.update(Suppliers,id) .with (suppliers[0]);
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}
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// TODO: remove test code
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{
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// one server: returns AdminService.Suppliers
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// two servers: returns API_BUSINESS_PARTNER.A_BusinessPartner
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const tx = S4bupa.tx({});
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let result = await tx.run(SELECT('*').from ('AdminService.Suppliers') .where ('ID =', 'ACME'));
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tx.commit();
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console.log(result);
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}
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// TODO: remove test code
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{
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// one server: returns AdminService.Suppliers
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// two servers: returns AdminService.Suppliers
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const tx = db.tx({});
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let result = await db.run(SELECT('*').from ('AdminService.Suppliers') .where ('ID =', 'ACME'));
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tx.commit();
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console.log(result);
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}
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}
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