69 lines
2.6 KiB
TypeScript
69 lines
2.6 KiB
TypeScript
import { getStateSnapshot, sseFrame } from '@/lib/game/state';
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import { subscribe } from '@/lib/sse';
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// ISS-129 (v0.57.0): Server-Sent Events feed of state snapshots — the current snapshot on connect,
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// then one after every sim tick (broadcast from lib/sim/engine.ts). One-way push; player actions
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// stay REST POSTs. Heartbeats keep idle proxies from dropping the connection. ISS-133 (v0.59.0):
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// frames carry the sseFrame projection (terminal package history dropped) — same shape as the
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// pushed frames, so a connect never costs one full-history frame.
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const encoder = new TextEncoder();
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const HEARTBEAT_MS = 15_000;
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export async function GET() {
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let heartbeat: ReturnType<typeof setInterval> | null = null;
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let unsubscribe: (() => void) | null = null;
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const cleanup = () => {
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if (heartbeat !== null) clearInterval(heartbeat);
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if (unsubscribe !== null) unsubscribe();
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};
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const stream = new ReadableStream<Uint8Array>({
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start(controller) {
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// Snapshot FIRST, then subscribe — a broadcast can never land before the initial event, so
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// events are strictly ordered by sim clock. A tick in the gap just means the client waits ≤1 s
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// for the next push instead of seeing an out-of-order frame.
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getStateSnapshot()
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.then((snapshot) => {
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unsubscribe = subscribe((text) => {
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try {
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// broadcast carries the bare snapshot JSON — wrap it in an SSE frame here (the route owns
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// wire framing, matching the initial snapshot + heartbeat above; lib/sse stays generic).
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controller.enqueue(encoder.encode(`data: ${text}\n\n`));
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} catch {
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// stream already closed — cleanup runs on cancel
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}
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});
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heartbeat = setInterval(() => {
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try {
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controller.enqueue(encoder.encode(': ping\n\n'));
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} catch {
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// same as above
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}
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}, HEARTBEAT_MS);
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controller.enqueue(encoder.encode(`data: ${JSON.stringify(sseFrame(snapshot))}\n\n`));
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})
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.catch(() => {
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cleanup();
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try {
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controller.close();
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} catch {
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// already closed
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}
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});
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},
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cancel() {
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cleanup(); // client went away — drop the subscription + heartbeat
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},
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});
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return new Response(stream, {
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headers: {
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'Content-Type': 'text/event-stream',
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'Cache-Control': 'no-cache',
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Connection: 'keep-alive',
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'X-Accel-Buffering': 'no', // prod sits behind Traefik — don't buffer the stream
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},
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});
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}
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