LearnSpace: full-stack educational whiteboard platform

Node.js/Express backend + vanilla JS frontend.
Features: real-time collaborative whiteboard (SSE), multi-page support,
LaTeX formulas, shapes/connectors, coordinate systems, number lines,
compass, zoom/pan, Catmull-Rom pencil smoothing, ruler/protractor with
rotation & resize controls, minimap navigation overlay, auto-measurements,
multi-page thumbnails sidebar, PNG export, page templates.
Student/teacher workflows: classes, assignments, library, dashboard.
Mobile responsive. SQLite (better-sqlite3).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/utils/logger.js

@@ -0,0 +1,61 @@
+'use strict';
+
+/* ── Structured logger — JSON in prod, pretty in dev ──────────────────────
+   Usage:  logger.info('msg', { key: val })
+           logger.error('msg', { err: e.message })
+   ──────────────────────────────────────────────────────────────────────── */
+
+const LEVELS = { error: 0, warn: 1, info: 2, debug: 3 };
+
+const COLORS = {
+  error: '\x1b[31m',   // red
+  warn:  '\x1b[33m',   // yellow
+  info:  '\x1b[36m',   // cyan
+  debug: '\x1b[90m',   // gray
+};
+const RESET = '\x1b[0m';
+
+const isProd = process.env.NODE_ENV === 'production';
+
+function _currentLevel() {
+  const env = process.env.LOG_LEVEL;
+  if (env && LEVELS[env] !== undefined) return LEVELS[env];
+  return isProd ? LEVELS.info : LEVELS.debug;
+}
+
+function log(level, msg, meta) {
+  if (LEVELS[level] > _currentLevel()) return;
+
+  const ts = new Date().toISOString();
+
+  if (isProd) {
+    /* JSON — one line per entry, parseable by log aggregators */
+    const entry = { level, ts, msg };
+    if (meta && typeof meta === 'object') Object.assign(entry, meta);
+    process.stdout.write(JSON.stringify(entry) + '\n');
+  } else {
+    /* Pretty — coloured label + message + optional meta */
+    const color = COLORS[level] || '';
+    const label = `[${ts}] ${color}${level.toUpperCase().padEnd(5)}${RESET}`;
+    const metaStr = meta && Object.keys(meta).length
+      ? ' ' + JSON.stringify(meta, null, 0)
+      : '';
+    process.stdout.write(`${label} ${msg}${metaStr}\n`);
+  }
+}
+
+const logger = {
+  error: (msg, meta) => log('error', msg, meta),
+  warn:  (msg, meta) => log('warn',  msg, meta),
+  info:  (msg, meta) => log('info',  msg, meta),
+  debug: (msg, meta) => log('debug', msg, meta),
+
+  /* Convenience: log an Error object */
+  exception: (msg, err, meta) => log('error', msg, {
+    err: err?.message,
+    stack: !isProd ? err?.stack : undefined,
+    ...meta,
+  }),
+};
+
+module.exports = logger;