import { createFileRoute } from '@tanstack/react-router'
import { subscribeToChatEvents, ensureBusStarted } from '../../server/chat-event-bus'

export const Route = createFileRoute('/api/events')({
  server: {
    handlers: {
      GET: async () => {
        await ensureBusStarted()

        const encoder = new TextEncoder()
        let unsubscribe: (() => void) | null = null
        let keepaliveInterval: ReturnType<typeof setInterval> | null = null

        const stream = new ReadableStream({
          start(controller) {
            // Send connected event immediately
            controller.enqueue(
              encoder.encode(`event: connected\ndata: ${JSON.stringify({ ts: Date.now() })}\n\n`),
            )

            // Subscribe to chat event bus
            unsubscribe = subscribeToChatEvents((event) => {
              try {
                controller.enqueue(
                  encoder.encode(`event: ${event.event}\ndata: ${JSON.stringify(event.data)}\n\n`),
                )
              } catch {
                // Stream closed
              }
            })

            // Keepalive every 15s
            keepaliveInterval = setInterval(() => {
              try {
                controller.enqueue(encoder.encode(`: keepalive\n\n`))
              } catch {
                // Stream closed
              }
            }, 15_000)
          },
          cancel() {
            if (unsubscribe) unsubscribe()
            if (keepaliveInterval) clearInterval(keepaliveInterval)
          },
        })

        return new Response(stream, {
          status: 200,
          headers: {
            'Content-Type': 'text/event-stream',
            'Cache-Control': 'no-cache, no-store',
            'Connection': 'keep-alive',
            'X-Accel-Buffering': 'no',
          },
        })
      },
    },
  },
})