75 lines
3.2 KiB
JavaScript
75 lines
3.2 KiB
JavaScript
const cds = require('@sap/cds')
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module.exports = cds.service.impl(async () => {
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// We are mashing up three services...
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const bupa = await cds.connect.to('API_BUSINESS_PARTNER')
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const admin = await cds.connect.to('AdminService')
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const db = await cds.connect.to('db')
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// Using reflected definitions from connected services/database
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const { Addresses: externalAddresses } = bupa.entities // projection on external addresses
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const { Books, Addresses } = db.entities('sap.capire.bookshop') // entities in local database
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// Delegate ValueHelp requests to S/4 backend, fetching current user's addresses from there
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admin.on('READ', 'Addresses', req => {
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console.log('Delegating to S/4 bupa service...')
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const UsersAddresses = SELECT.from(externalAddresses).where({ contact: req.user.id }).where(req.query.SELECT.where)
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return bupa.tx(req).run(UsersAddresses)
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})
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// Replicate chosen addresses from S/4 when filling orders.
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admin.before('PATCH', 'Orders', async req => {
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const assigned = { ID: req.data.shippingAddress_ID, contact: req.user.id }
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if (!assigned.ID) return //> something else
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const local = db.transaction(req)
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const [replica] = await local.read(Addresses).where(assigned)
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if (replica) return //> already replicated
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const [address] = await bupa.tx(req).run(SELECT.from(externalAddresses).where(assigned))
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if (address) return local.create(Addresses).entries(address)
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})
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// Subscribe to S/4 event to update local replicas when sources change in S/4.
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bupa.on('BusinessPartner/Changed', async msg => {
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console.log('>> received:', msg.data)
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const BuPaID = msg.data.KEY[0].BUSINESSPARTNER //> S/4HANA's weird payload format
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const { SELECT, UPDATE } = cds.ql(msg) //> convenient alternative to <srv>.transaction(req).run(SELECT...)
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// fetch affected entries from local replicas
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const replicas = await SELECT.from(Addresses).where({ contact: BuPaID })
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if (replicas.length === 0) return //> not affected
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// fetch changed data from S/4 -> might be less than local due to deletes
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const changed = await SELECT.from(externalAddresses).where({
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contact: BuPaID, ID: replicas.map(({ ID }) => ID)
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})
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// update local replicas with changes from S/4
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const local = db.transaction(msg) //> using that variant to benefit from bulk runs
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return local.run(changed.map(a => UPDATE(Addresses, a.ID).with(a)))
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})
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// Validate incoming orders and reduce books' stocks.
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admin.before('CREATE', 'Orders', async req => {
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const { Items } = req.data
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// validate input...
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if (!Items || Items.length === 0) return req.reject('Please order at least one item.')
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if (!req.data.shippingAddress_ID) return req.reject('Please enter a valid shipping address.', 'shippingAddress_ID')
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// reduce stock on ordered books...
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const all = await db.tx(req).run(
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Items.map(each =>
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UPDATE(Books)
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.where('ID =', each.book_ID)
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.and('stock >=', each.amount)
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.set('stock -=', each.amount)
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)
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)
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all.forEach(
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(affectedRows, i) =>
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affectedRows > 0 || req.error(409, `${Items[i].amount} exceeds stock for book #${Items[i].book_ID}`)
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)
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})
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})
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require('./utils')
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