const { status, header } = require('node-res')
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class SSE {
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constructor () {
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this.subscriptions = new Set()
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this.counter = 0
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}
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// Subscribe to a channel and set initial headers
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subscribe (req, res) {
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req.socket.setTimeout(0)
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status(res, 200)
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header(res, 'Content-Type', 'text/event-stream')
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header(res, 'Cache-Control', 'no-cache')
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if (req.httpVersion !== '2.0') {
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header(res, 'Connection', 'keep-alive')
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}
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this.subscriptions.add(res)
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res.on('close', () => this.subscriptions.delete(res))
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this.broadcast('ready', {})
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}
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// Publish event and data to all connected clients
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broadcast (event, data) {
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this.counter++
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// Do console.log(this.subscriptions.size) to see, if there are any memory leaks
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for (const res of this.subscriptions) {
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this.clientBroadcast(res, event, data)
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}
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}
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// Publish event and data to a given response object
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clientBroadcast (res, event, data) {
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res.write(`id: ${this.counter}\n`)
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res.write('event: message\n')
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res.write(`data: ${JSON.stringify({ event, ...data })}\n\n`)
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}
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}
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module.exports = SSE
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