first commit

api/app/services/sse.ts

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+import { PassThrough } from 'node:stream'
+import type { HttpContext } from '@adonisjs/core/http'
+
+export interface SseChannel {
+  /**
+   * Sends one event to the browser. Ignored once the connection is closed.
+   */
+  send(event: string, data: unknown): void
+
+  /**
+   * Registers a callback invoked once, when the browser disconnects or the
+   * channel is closed by the server.
+   */
+  onClose(callback: () => void): void
+
+  close(): void
+}
+
+/**
+ * Turns the response into a Server-Sent Events stream (used with
+ * EventSource on the Angular side for the live metrics, logs and jobs).
+ */
+export function openSse({ response }: HttpContext): SseChannel {
+  const stream = new PassThrough()
+  const closeCallbacks: (() => void)[] = []
+  let closed = false
+
+  response.header('Content-Type', 'text/event-stream; charset=utf-8')
+  response.header('Cache-Control', 'no-cache, no-transform')
+  response.header('Connection', 'keep-alive')
+  response.header('X-Accel-Buffering', 'no')
+  response.stream(stream)
+
+  /**
+   * Comments keep the connection open through Caddy and let the browser
+   * know quickly that the stream is established.
+   */
+  stream.write('retry: 5000\n\n')
+  const heartbeat = setInterval(() => stream.write(': ping\n\n'), 25_000)
+
+  const close = () => {
+    if (closed) return
+    closed = true
+    clearInterval(heartbeat)
+    for (const callback of closeCallbacks) callback()
+    stream.end()
+  }
+
+  /**
+   * "close" on the response (not the request) is emitted when the browser
+   * goes away.
+   */
+  response.response.on('close', close)
+
+  return {
+    send(event, data) {
+      if (closed) return
+      stream.write(`event: ${event}\ndata: ${JSON.stringify(data)}\n\n`)
+    },
+    onClose(callback) {
+      closeCallbacks.push(callback)
+    },
+    close,
+  }
+}