22 lines
669 B
JavaScript
22 lines
669 B
JavaScript
const cds = require('@sap/cds')
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module.exports = cds.service.impl(function() {
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const { Books } = cds.entities
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// Reduce stock of ordered books if available stock suffices
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this.before ('CREATE', 'Orders', (req) => {
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const { Items: OrderItems } = req.data
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return cds.transaction(req) .run (OrderItems.map (order =>
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UPDATE (Books) .where ('ID =', order.book_ID)
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.and ('stock >=', order.amount)
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.set ('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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})
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