40 lines
1.8 KiB
JavaScript
40 lines
1.8 KiB
JavaScript
const cds = require('@sap/cds')
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module.exports = cds.service.impl((srv) => {
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// Get the CSN definition for Reviews from the db schema for sub-sequent queries
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// ( Note: we explicitly specify the namespace to support embedded reuse )
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const { Reviews, Likes } = cds.entities('sap.capire.reviews')
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// Increment counter for reviews considered helpful
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srv.on ('like', (req) => {
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if (!req.user) return req.reject(400, 'You must be identified to like a review')
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const {review} = req.data, {user} = req
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const tx = cds.transaction(req)
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return tx.run ([
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INSERT.into (Likes) .entries ({review_ID: review, user: user.id}),
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UPDATE (Reviews) .set({liked: {'+=': 1}}) .where({ID:review})
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]).catch(() => req.reject(400, 'You already liked that review'))
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})
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// Delete a former like by the same user
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srv.on('unlike', async (req) => {
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if (!req.user) return req.reject(400, 'You must be identified to remove a former like of yours')
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const { review } = req.data, { user } = req
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const tx = cds.transaction(req)
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const affectedRows = await tx.run(DELETE.from(Likes).where({ review_ID: review, user: user.id }))
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if (affectedRows === 1) return tx.run(UPDATE(Reviews).set({ liked: { '-=': 1 } }).where({ ID: review }))
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})
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// Emit an event to inform subscribers about new avg ratings for reviewed subjects
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// ( Note: req.on.succeeded ensures we only do that if there's no error )
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srv.after(['CREATE', 'UPDATE', 'DELETE'], 'Reviews', async (_, req) => {
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const { subject } = req.data
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const { rating } = await cds.transaction(req).run(
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SELECT.one(['avg(rating) as rating']).from(Reviews).where({ subject })
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)
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req.on('succeeded', () => {
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srv.emit('reviewed', { subject, rating })
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console.log(`Reviewed event was emitted for book "${subject}" with rating ${rating}.`)
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})
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})
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}) |