Initial Comming

server/sync-server.js

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+import 'dotenv/config';
+import express from 'express';
+import { createServer } from 'http';
+import { WebSocketServer } from 'ws';
+import { readFileSync } from 'fs';
+import { fileURLToPath } from 'url';
+import { dirname, join } from 'path';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const ROOT = join(__dirname, '..');
+
+const PORT = process.env.PORT || 34034;
+const TICK_HZ = Number(process.env.TICK_HZ || 20); // server broadcast rate
+
+// ---- Load scene ----------------------------------------------------------
+function loadScene() {
+  const raw = readFileSync(join(ROOT, 'data', 'scene.json'), 'utf-8');
+  return JSON.parse(raw);
+}
+let scene = loadScene();
+
+// ---- Motion solvers ------------------------------------------------------
+// Every solver takes (spawn, tSeconds) and returns { x,y,z, yawDeg }.
+// Positions are in world millimetres, matching scene.json.
+
+function solveHover(spawn, t) {
+  const p = spawn.position;
+  const r = spawn.hoverRadiusMm ?? 0;
+  const hoverW = (2 * Math.PI) / (spawn.hoverPeriodS ?? 6);
+  const bobA = spawn.bobAmplitudeMm ?? 0;
+  const bobW = (2 * Math.PI) / (spawn.bobPeriodS ?? 3);
+  const yaw = ((spawn.yawDegPerS ?? 0) * t) % 360;
+  return {
+    x: p.x + Math.cos(hoverW * t) * r,
+    y: p.y + Math.sin(bobW * t) * bobA,
+    z: p.z + Math.sin(hoverW * t) * r,
+    yawDeg: yaw,
+  };
+}
+
+function solvePatrol(spawn, t) {
+  const path = spawn.path || [];
+  if (path.length === 0) return { x: 0, y: 0, z: 0, yawDeg: 0 };
+  if (path.length === 1) return { ...path[0], yawDeg: 0 };
+  const period = spawn.patrolPeriodS ?? 12;
+  const segCount = path.length; // looped path
+  const phase = ((t % period) / period) * segCount; // 0..segCount
+  const seg = Math.floor(phase) % segCount;
+  const frac = phase - Math.floor(phase);
+  const a = path[seg];
+  const b = path[(seg + 1) % segCount];
+  const x = a.x + (b.x - a.x) * frac;
+  const y = a.y + (b.y - a.y) * frac;
+  const z = a.z + (b.z - a.z) * frac;
+  const bobA = spawn.bobAmplitudeMm ?? 0;
+  const bobW = (2 * Math.PI) / (spawn.bobPeriodS ?? 3);
+  let yawDeg = 0;
+  if (spawn.faceTravel) {
+    yawDeg = (Math.atan2(b.x - a.x, b.z - a.z) * 180) / Math.PI;
+  }
+  return { x, y: y + Math.sin(bobW * t) * bobA, z, yawDeg };
+}
+
+const SOLVERS = { hover: solveHover, patrol: solvePatrol };
+
+function solveSpawn(spawn, t) {
+  const solver = SOLVERS[spawn.motion] || solveHover;
+  return solver(spawn, t);
+}
+
+// ---- Authoritative state -------------------------------------------------
+const startTime = Date.now();
+function nowSeconds() {
+  return (Date.now() - startTime) / 1000;
+}
+
+function buildSnapshot() {
+  const t = nowSeconds();
+  const ghosts = scene.spawns.map((spawn) => {
+    const pose = solveSpawn(spawn, t);
+    return {
+      spawnId: spawn.id,
+      ghostId: spawn.ghostId,
+      label: spawn.label,
+      pos: { x: round(pose.x), y: round(pose.y), z: round(pose.z) },
+      yawDeg: round(pose.yawDeg),
+    };
+  });
+  return { type: 'state', serverTime: t, ghosts };
+}
+
+function round(n) {
+  return Math.round(n * 10) / 10;
+}
+
+// ---- HTTP + static -------------------------------------------------------
+const app = express();
+app.use(express.static(join(ROOT, 'public')));
+
+// Scene metadata (anchors + spawn definitions) for clients to align/render.
+app.get('/api/scene', (_req, res) => {
+  res.json({
+    world: scene.world,
+    anchors: scene.anchors,
+    spawns: scene.spawns.map((s) => ({
+      id: s.id,
+      ghostId: s.ghostId,
+      label: s.label,
+      motion: s.motion,
+    })),
+  });
+});
+
+app.get('/api/health', (_req, res) => {
+  res.json({ ok: true, viewers: wss ? wss.clients.size : 0, tickHz: TICK_HZ });
+});
+
+const httpServer = createServer(app);
+
+// ---- WebSocket broadcast -------------------------------------------------
+const wss = new WebSocketServer({ server: httpServer, path: '/sync' });
+
+wss.on('connection', (socket) => {
+  // Send scene + immediate snapshot on connect so a new phone is instantly aligned.
+  socket.send(JSON.stringify({ type: 'hello', world: scene.world, anchors: scene.anchors }));
+  socket.send(JSON.stringify(buildSnapshot()));
+});
+
+setInterval(() => {
+  if (wss.clients.size === 0) return;
+  const payload = JSON.stringify(buildSnapshot());
+  for (const client of wss.clients) {
+    if (client.readyState === 1) client.send(payload);
+  }
+}, 1000 / TICK_HZ);
+
+httpServer.listen(PORT, () => {
+  console.log(`Newbury exhibit sync server on :${PORT} (broadcast ${TICK_HZ}Hz)`);
+  console.log(`  Viewer:  http://localhost:${PORT}/`);
+  console.log(`  Scene:   ${scene.spawns.length} spawns, ${scene.anchors.length} anchors`);
+});