29 lines
1.1 KiB
JavaScript
29 lines
1.1 KiB
JavaScript
const cds = require('@sap/cds')
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const { Books } = cds.entities
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/** Service implementation for CatalogService */
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module.exports = cds.service.impl(srv => {
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srv.after ('READ', 'Books', each => each.stock > 111 && _addDiscount2(each,11))
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srv.before ('CREATE', 'Orders', _reduceStock)
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// srv.before ('*', (req) => { console.debug ('>>>', req.method, req.target.name) })
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})
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/** Add some discount for overstocked books */
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function _addDiscount2 (each,discount) {
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each.title += ` -- ${discount}% discount!`
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}
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/** Reduce stock of ordered books if available stock suffices */
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async function _reduceStock (req) {
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const { Items: OrderItems } = req.data
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// req.on('failed', () => { console.debug ('>>> failed for order', req.data.ID) })
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return cds.transaction(req) .run (()=> OrderItems.map (order =>
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UPDATE (Books) .set ('stock -=', order.amount)
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.where ('ID =', order.book_ID) .and ('stock >=', order.amount)
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)) .then (all => all.forEach ((affectedRows,i) => {
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if (affectedRows === 0) req.error (409,
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`${OrderItems[i].amount} exceeds stock for book #${OrderItems[i].book_ID}`
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)
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}))
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}
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