newbury-exhibit/server/sync-server.js

import 'dotenv/config';
import express from 'express';
import { createServer } from 'http';
import { WebSocketServer } from 'ws';
import { readFileSync, writeFileSync, copyFileSync, existsSync, mkdirSync } 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 ----------------------------------------------------------
// Two files:
//   data/scene.json       -> committed "seed" (tracked in git). Default/first-run.
//   data/scene.live.json  -> authored scene written by the admin (git-IGNORED),
//                            so `git reset --hard` on deploy never clobbers it.
// We read live if it exists, else fall back to the seed. Saves always go to live.
const SEED_PATH = join(ROOT, 'data', 'scene.json');
const LIVE_PATH = join(ROOT, 'data', 'scene.live.json');

function loadScene() {
  const path = existsSync(LIVE_PATH) ? LIVE_PATH : SEED_PATH;
  return JSON.parse(readFileSync(path, 'utf-8'));
}
let scene = loadScene();

// ---- Ghost roster (for the admin picker) ---------------------------------
// Full enriched roster lives in data/ghosts.json. We serve a trimmed view with
// just what the scene editor needs to pick a ghost and auto-fill its colour.
let roster = [];
try {
  const rraw = readFileSync(join(ROOT, 'data', 'ghosts.json'), 'utf-8');
  roster = JSON.parse(rraw).map((g) => ({
    id: g.id, name: g.name, color: g.color, rarity: g.rarity,
    rarityTier: g.rarityTier, isBoss: !!g.isBoss, ability: g.abilityId,
  }));
} catch (_) {
  roster = []; // roster optional; editor falls back to free-text id
}

// ---- 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.json({ limit: '4mb' })); // for the admin save endpoint
app.use(express.static(join(ROOT, 'public')));

// Full scene for the admin editor (everything) and clients (anchors+spawns).
app.get('/api/scene', (_req, res) => {
  res.json(scene);
});

// Ghost roster for the admin picker (trimmed).
app.get('/api/ghosts', (_req, res) => {
  res.json(roster);
});

// Admin save: validate, back up the old file, write, hot-reload.
app.post('/api/scene', (req, res) => {
  const incoming = req.body;
  const err = validateScene(incoming);
  if (err) return res.status(400).json({ ok: false, error: err });
  try {
    const dataDir = join(ROOT, 'data');
    const target = LIVE_PATH; // authored scene -> live file (survives deploys)
    // timestamped backup so a bad save is always recoverable
    const backupDir = join(dataDir, 'backups');
    if (!existsSync(backupDir)) mkdirSync(backupDir, { recursive: true });
    if (existsSync(target)) {
      const stamp = new Date().toISOString().replace(/[:.]/g, '-');
      copyFileSync(target, join(backupDir, `scene-${stamp}.json`));
    }
    writeFileSync(target, JSON.stringify(incoming, null, 2), 'utf-8');
    scene = incoming;            // hot-reload: live ghosts update immediately
    broadcastHello();            // push new anchors/world to connected viewers
    res.json({ ok: true, spawns: scene.spawns.length, anchors: scene.anchors.length, blockers: (scene.blockers || []).length });
  } catch (e) {
    res.status(500).json({ ok: false, error: String(e.message || e) });
  }
});

// Minimal schema guard so a malformed save can't crash the motion loop.
function validateScene(s) {
  if (!s || typeof s !== 'object') return 'scene must be an object';
  if (!s.world || !s.world.buildSize) return 'missing world.buildSize';
  if (!Array.isArray(s.anchors)) return 'anchors must be an array';
  if (!Array.isArray(s.spawns)) return 'spawns must be an array';
  if (s.blockers && !Array.isArray(s.blockers)) return 'blockers must be an array';
  for (const sp of s.spawns) {
    if (!sp.id || !sp.motion) return `spawn missing id/motion: ${JSON.stringify(sp).slice(0, 80)}`;
    if (sp.motion === 'patrol' && (!Array.isArray(sp.path) || sp.path.length < 2)) {
      return `patrol spawn "${sp.id}" needs a path of >=2 points`;
    }
    if (sp.motion === 'hover' && !sp.position) return `hover spawn "${sp.id}" needs a position`;
  }
  return null;
}

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' });

function helloPayload() {
  return JSON.stringify({
    type: 'hello',
    world: scene.world,
    anchors: scene.anchors,
    blockers: scene.blockers || [],
  });
}

function broadcastHello() {
  const payload = helloPayload();
  for (const client of wss.clients) {
    if (client.readyState === 1) client.send(payload);
  }
}

wss.on('connection', (socket) => {
  // Send scene + immediate snapshot on connect so a new phone is instantly aligned.
  socket.send(helloPayload());
  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, ${scene.anchors.length} anchors` +
    ` (${existsSync(LIVE_PATH) ? 'live: scene.live.json' : 'seed: scene.json'})`);
});