40 lines
1.0 KiB
JavaScript
40 lines
1.0 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(function () {
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this.after(
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'READ',
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'Books',
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each => each.stock > 111 && _addDiscount2(each, 11)
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)
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this.before('CREATE', 'Orders', _reduceStock)
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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 += ` -- ${discount}% discount!`
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}
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/** Reduce stock of ordered books if available stock suffices */
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async function _reduceStock (req) {
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const { Items: OrderItems } = req.data
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const all = await cds.transaction(req).run(() =>
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OrderItems.map(order =>
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UPDATE(Books)
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.set('stock -=', order.amount)
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.where('ID =', order.book_ID)
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.and('stock >=', order.amount)
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)
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)
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all.forEach((affectedRows, i) => {
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if (affectedRows === 0)
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req.error(
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409,
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`${OrderItems[i].amount} exceeds stock for book #${
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OrderItems[i].book_ID
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}`
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)
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})
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}
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