Palvelimen lähettämät tapahtumat reittikäsittelijöistä

// app/api/sse/route.ts
import { NextRequest } from 'next/server';

export const dynamic = 'force-dynamic'; // never cache this route

export function GET(_req: NextRequest): Response {
  const stream = new ReadableStream({
    start(controller) {
      const encoder = new TextEncoder();

      // Send one event immediately
      controller.enqueue(
        encoder.encode('data: {"message":"connected"}\n\n')
      );

      // Close after the first message (demo only)
      controller.close();
    },
  });

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

// app/api/ticker/route.ts
import { NextRequest } from 'next/server';

export const dynamic = 'force-dynamic';

export function GET(_req: NextRequest): Response {
  const encoder = new TextEncoder();
  let intervalId: ReturnType<typeof setInterval>;
  let counter = 0;

  const stream = new ReadableStream({
    start(controller) {
      intervalId = setInterval(() => {
        const payload = JSON.stringify({ tick: ++counter, ts: Date.now() });
        controller.enqueue(encoder.encode(`data: ${payload}\n\n`));
      }, 1000);
    },
    cancel() {
      // Called when the client closes the connection
      clearInterval(intervalId);
      console.log('SSE client disconnected — interval cleared');
    },
  });

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

// app/api/events/route.ts
import { NextRequest } from 'next/server';

export const dynamic = 'force-dynamic';

function encodeEvent(id: number, event: string, data: unknown): Uint8Array {
  const encoder = new TextEncoder();
  const frame =
    `id: ${id}\n` +
    `event: ${event}\n` +
    `data: ${JSON.stringify(data)}\n\n`;
  return encoder.encode(frame);
}

export function GET(req: NextRequest): Response {
  const lastId = Number(req.headers.get('last-event-id') ?? '0');
  let id = lastId;
  let intervalId: ReturnType<typeof setInterval>;

  const stream = new ReadableStream({
    start(controller) {
      intervalId = setInterval(() => {
        id++;
        controller.enqueue(
          encodeEvent(id, 'notification', { message: `Event ${id}` })
        );
      }, 2000);
    },
    cancel() {
      clearInterval(intervalId);
    },
  });

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

'use client';
import { useEffect, useState } from 'react';

type Tick = { tick: number; ts: number };

export default function LiveTicker() {
  const [latest, setLatest] = useState<Tick | null>(null);

  useEffect(() => {
    const source = new EventSource('/api/ticker');

    source.onmessage = (e: MessageEvent<string>) => {
      setLatest(JSON.parse(e.data) as Tick);
    };

    source.onerror = () => {
      // EventSource will reconnect automatically after 3 s (default)
      console.warn('SSE error — browser will retry');
    };

    return () => source.close(); // cleanup on unmount
  }, []);

  if (!latest) return <p>Waiting for first tick…</p>;
  return (
    <p>
      Tick <strong>{latest.tick}</strong> received at{' '}
      {new Date(latest.ts).toLocaleTimeString()}
    </p>
  );
}

// Simplified in-memory event log (single-instance demo)
const recentEvents: Array<{ id: number; data: string }> = [];
let globalId = 0;

export function recordEvent(data: string) {
  globalId++;
  recentEvents.push({ id: globalId, data });
  if (recentEvents.length > 100) recentEvents.shift(); // ring buffer
}

export function getEventsSince(lastId: number) {
  return recentEvents.filter((e) => e.id > lastId);
}

// In the Route Handler:
// const missed = getEventsSince(Number(req.headers.get('last-event-id') ?? '0'));
// for (const e of missed) controller.enqueue(encodeEvent(e.id, 'update', e.data));

// app/api/live/route.ts
import { NextRequest } from 'next/server';

export const dynamic = 'force-dynamic';

export function GET(req: NextRequest): Response {
  const encoder = new TextEncoder();
  let closed = false;
  let intervalId: ReturnType<typeof setInterval>;

  const stream = new ReadableStream({
    start(controller) {
      req.signal.addEventListener('abort', () => {
        closed = true;
        clearInterval(intervalId);
        controller.close();
      });

      intervalId = setInterval(() => {
        if (closed) return;
        const data = JSON.stringify({ time: new Date().toISOString() });
        controller.enqueue(encoder.encode(`data: ${data}\n\n`));
      }, 1000);
    },
    cancel() {
      closed = true;
      clearInterval(intervalId);
    },
  });

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

// lib/sse-bus.ts — singleton EventEmitter (single-instance only)
import { EventEmitter } from 'events';

const bus = new EventEmitter();
bus.setMaxListeners(500); // raise limit for many concurrent clients

export default bus;

// --- app/api/updates/route.ts ---
// import bus from '@/lib/sse-bus';
// import { NextRequest } from 'next/server';
//
// export function GET(req: NextRequest): Response {
//   const encoder = new TextEncoder();
//   let closed = false;
//
//   const stream = new ReadableStream({
//     start(controller) {
//       const handler = (payload: unknown) => {
//         if (closed) return;
//         controller.enqueue(
//           encoder.encode(`data: ${JSON.stringify(payload)}\n\n`)
//         );
//       };
//       bus.on('update', handler);
//       req.signal.addEventListener('abort', () => {
//         closed = true;
//         bus.off('update', handler);
//         controller.close();
//       });
//     },
//   });
//
//   return new Response(stream, { headers: { 'Content-Type': 'text/event-stream', 'Cache-Control': 'no-cache', Connection: 'keep-alive' } });
// }

// Helper that formats a full SSE preamble with retry hint
function sseHeaders(): HeadersInit {
  return {
    'Content-Type': 'text/event-stream',
    'Cache-Control': 'no-cache, no-transform',
    Connection: 'keep-alive',
  };
}

function retryFrame(ms: number): string {
  return `retry: ${ms}\n\n`;
}

// Unauthorized? Close with 204 to suppress browser retry loop
function unauthorizedSSE(): Response {
  return new Response(null, { status: 204 });
}

// Usage in route:
// const token = req.nextUrl.searchParams.get('token');
// if (!isValid(token)) return unauthorizedSSE();
// controller.enqueue(encoder.encode(retryFrame(5000)));

// Run your Next.js dev server, then in a second terminal:
// curl -N -H 'Accept: text/event-stream' http://localhost:3000/api/ticker
//
// Expected output (one block per second):
// data: {"tick":1,"ts":1718000001000}
//
// data: {"tick":2,"ts":1718000002000}
//
// Replay from a specific event ID:
// curl -N -H 'Last-Event-ID: 10' http://localhost:3000/api/events

// TypeScript utility — build SSE test frames in unit tests
function parseSSEFrame(raw: string): Record<string, string> {
  const result: Record<string, string> = {};
  for (const line of raw.split('\n')) {
    const colon = line.indexOf(':');
    if (colon === -1) continue;
    const key = line.slice(0, colon).trim();
    const value = line.slice(colon + 1).trim();
    result[key] = value;
  }
  return result;
}

console.log(parseSSEFrame('id: 5\nevent: tick\ndata: {"n":5}\n'));