34 lines
1.1 KiB
JavaScript
34 lines
1.1 KiB
JavaScript
const cds = require('@sap/cds')
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class CatalogService extends cds.ApplicationService { init(){
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// Reflect entities from model
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const { Books } = cds.entities ('sap.capire.bookshop')
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// Reduce stock of ordered books if available stock suffices
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this.on ('submitOrder', async req => {
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const {book,amount} = req.data
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// Read stock from database
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let {stock} = await SELECT.from (Books, book, b => b.stock)
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if (stock >= amount) {
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// Reduce stock by ordered amount
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await UPDATE (Books,book) .with ({ stock: stock -= amount })
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// Emit event to inform others
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await this.emit ('OrderedBook', { book, amount, buyer:req.user.id })
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// Return reduced stock to caller
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return req.reply ({ stock })
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}
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// Return error about insufficient stock
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else return req.error (409,`${amount} exceeds stock for book #${book}`)
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})
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// Add some discount for overstocked books
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this.after ('READ','Books', each => {
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if (each.stock > 111) each.title += ` -- 11% discount!`
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})
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return super.init()
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}}
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module.exports = { CatalogService }
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