server.js

// ============================================================================
// EyeLS — Node.js (Express) server
//
// Responsibilities:
//   1. Serve the static front-end (HTML / CSS / JS / eyels.js).
//   2. Expose a small REST API:
//        POST /api/stats        text -> JSON stats (delegated to the C++ binary)
//        POST /api/sessions     persist a typed session
//        GET  /api/sessions     list all persisted sessions
//        GET  /api/sessions/:id fetch one session
//        DELETE /api/sessions/:id
//        GET  /api/health       basic introspection (stack info)
//
// The /api/stats endpoint shells out to ./tools/stats (a C++ program) so that
// the heavy text-crunching happens in native code — Node just streams data
// in and pipes JSON back out.
// ============================================================================

'use strict';

const express = require('express');
const path = require('path');
const fs = require('fs');
const { spawn } = require('child_process');

const ROOT = __dirname;
const STATS_BIN = path.join(ROOT, 'tools', 'stats');
const DATA_DIR = path.join(ROOT, 'data');
const SESSIONS_FILE = path.join(DATA_DIR, 'sessions.json');
const PORT = Number(process.env.PORT) || 3000;

const app = express();
app.use(express.json({ limit: '2mb' }));

// --------------------------------------------------------------------------
// Static front-end
// --------------------------------------------------------------------------
app.use(
  express.static(ROOT, {
    // Don't auto-serve index.html from /; we want explicit routes below so
    // the URL bar reflects the active view.
    index: false,
    extensions: ['html'],
  })
);

app.get('/', (_req, res) => res.sendFile(path.join(ROOT, 'index.html')));
app.get('/stats', (_req, res) => res.sendFile(path.join(ROOT, 'stats.html')));
app.get('/settings', (_req, res) =>
  res.sendFile(path.join(ROOT, 'settings.html'))
);

// --------------------------------------------------------------------------
// Sessions persistence (simple JSON file — fine for a personal app)
// --------------------------------------------------------------------------
function loadSessions() {
  try {
    return JSON.parse(fs.readFileSync(SESSIONS_FILE, 'utf-8'));
  } catch {
    return [];
  }
}

function saveSessions(sessions) {
  fs.mkdirSync(DATA_DIR, { recursive: true });
  fs.writeFileSync(SESSIONS_FILE, JSON.stringify(sessions, null, 2));
}

// --------------------------------------------------------------------------
// /api/stats — shell out to the C++ binary
// --------------------------------------------------------------------------
function runStats(text) {
  return new Promise((resolve, reject) => {
    if (!fs.existsSync(STATS_BIN)) {
      return reject(
        new Error(
          'C++ stats binary not found. Build it with: `make -C tools` ' +
            '(or `npm run build:cpp`).'
        )
      );
    }
    const child = spawn(STATS_BIN, [], { stdio: ['pipe', 'pipe', 'pipe'] });
    let out = '';
    let err = '';
    child.stdout.on('data', (d) => (out += d.toString('utf8')));
    child.stderr.on('data', (d) => (err += d.toString('utf8')));
    child.on('error', (e) => reject(e));
    child.on('close', (code) => {
      if (code !== 0) {
        return reject(
          new Error(`stats binary exited ${code}: ${err.trim() || '(no stderr)'}`)
        );
      }
      try {
        resolve(JSON.parse(out));
      } catch (parseErr) {
        reject(new Error(`invalid JSON from stats binary: ${parseErr.message}`));
      }
    });
    child.stdin.end(text || '');
  });
}

app.post('/api/stats', async (req, res) => {
  const text = typeof req.body.text === 'string' ? req.body.text : '';
  try {
    const stats = await runStats(text);
    res.json({ ok: true, stats, generatedBy: 'C++ (./tools/stats)' });
  } catch (e) {
    res.status(500).json({ ok: false, error: e.message });
  }
});

// --------------------------------------------------------------------------
// /api/sessions
// --------------------------------------------------------------------------
app.get('/api/sessions', (_req, res) => {
  res.json({ ok: true, sessions: loadSessions() });
});

app.get('/api/sessions/:id', (req, res) => {
  const id = String(req.params.id);
  const session = loadSessions().find((s) => String(s.id) === id);
  if (!session) return res.status(404).json({ ok: false, error: 'not found' });
  res.json({ ok: true, session });
});

app.post('/api/sessions', (req, res) => {
  const text = typeof req.body.text === 'string' ? req.body.text : '';
  if (!text.trim()) {
    return res.status(400).json({ ok: false, error: 'empty text' });
  }
  const sessions = loadSessions();
  const session = {
    id: Date.now(),
    timestamp: new Date().toISOString(),
    text,
    characters: text.length,
  };
  sessions.unshift(session);
  // Keep the last 100 sessions to avoid unbounded growth.
  if (sessions.length > 100) sessions.length = 100;
  saveSessions(sessions);
  res.json({ ok: true, session });
});

app.delete('/api/sessions/:id', (req, res) => {
  const id = String(req.params.id);
  const sessions = loadSessions();
  const next = sessions.filter((s) => String(s.id) !== id);
  if (next.length === sessions.length) {
    return res.status(404).json({ ok: false, error: 'not found' });
  }
  saveSessions(next);
  res.json({ ok: true });
});

// --------------------------------------------------------------------------
// /api/health — for debugging which pieces of the stack are reachable
// --------------------------------------------------------------------------
app.get('/api/health', (_req, res) => {
  res.json({
    ok: true,
    node: process.version,
    statsBinaryAvailable: fs.existsSync(STATS_BIN),
    stack: {
      server: 'Node.js + Express',
      stats: 'C++ (./tools/stats)',
      mainApp: 'Vanilla JS + eyels.js gaze tracker',
      dashboard: 'Angular (/stats)',
      settings: 'Vue 3 (/settings)',
    },
  });
});

// --------------------------------------------------------------------------
// Boot
// --------------------------------------------------------------------------
app.listen(PORT, () => {
  // eslint-disable-next-line no-console
  console.log(`\n  EyeLS server running at http://localhost:${PORT}`);
  console.log(
    `  Stack: Node.js (Express)  +  C++ stats  +  Angular  +  Vue  +  Vanilla JS\n`
  );
  if (!fs.existsSync(STATS_BIN)) {
    console.warn(
      `  ⚠  C++ stats binary missing at ${STATS_BIN}.\n` +
        `     Build it with:  npm run build:cpp\n`
    );
  }
});