import { cluster, namespaces } from '@/lib/clusterMock'

/**
 * Mock stand-in for the real atlas `GET /api/stream`. Emits synthetic `topology` deltas on an
 * interval and a keepalive comment frame, matching the SSE shape the frontend expects — no real
 * informer, no real cluster.
 */
export async function GET(req: Request) {
  const encoder = new TextEncoder()
  let seq = cluster.generation

  const stream = new ReadableStream({
    start(controller) {
      const send = (event: string, data: unknown) => {
        controller.enqueue(encoder.encode(`event: ${event}\nid: ${seq++}\ndata: ${JSON.stringify(data)}\n\n`))
      }

      const keepalive = setInterval(() => {
        controller.enqueue(encoder.encode(': keepalive\n\n'))
      }, 30_000)

      const delta = setInterval(() => {
        const ns = namespaces[Math.floor(Math.random() * namespaces.length)]
        send('topology', { namespace: ns.name, running: ns.running, total: ns.total })
      }, 5_000)

      req.signal.addEventListener('abort', () => {
        clearInterval(keepalive)
        clearInterval(delta)
        controller.close()
      })
    },
  })

  return new Response(stream, {
    headers: {
      'Content-Type': 'text/event-stream',
      'Cache-Control': 'no-cache',
      Connection: 'keep-alive',
    },
  })
}