// ─────────────────────────────────────────────────────────────
// src/ua.js — minimal User-Agent parser.
//
// Coarse-grained classification only: device_type / os / browser.
// We deliberately do NOT pull in ua-parser-js — the project keeps a
// small dependency footprint and we only need three buckets. The raw
// UA is also stored alongside parsed fields (see src/events.js) so a
// regex miss can be re-classified later.
//
// Also owns MOBILE_UA_RE — the existing /timeline view-dispatch
// regex used by server.js. Single source of truth.
// ─────────────────────────────────────────────────────────────

// UA substrings that mean "phone-class small screen". Tablets (iPad,
// Android tablets) deliberately do NOT match — they get the desktop
// view, which matches existing behaviour in server.js.
export const MOBILE_UA_RE =
  /\b(iPhone|iPod|Android.*Mobile|Mobile.*Firefox|IEMobile|BlackBerry|Opera Mini)\b/i;

// Tablet-class devices. Order matters in parseUA(): tablet check runs
// before mobile so "iPad" doesn't accidentally fall through to desktop.
const TABLET_UA_RE = /\b(iPad|Android(?!.*Mobile))\b/i;

export function parseUA(ua) {
  if (!ua || typeof ua !== 'string') {
    return { device_type: null, os: null, browser: null };
  }

  // device_type — fallback is 'desktop' to mirror server.js
  // wantsMobileView() (unrecognised UA → desktop page). Analytics
  // stay consistent with what the user actually saw.
  let device_type = 'desktop';
  if (TABLET_UA_RE.test(ua))      device_type = 'tablet';
  else if (MOBILE_UA_RE.test(ua)) device_type = 'mobile';

  // os
  let os = 'other';
  if      (/\b(iPhone|iPad|iPod)\b/.test(ua))   os = 'iOS';
  else if (/\bAndroid\b/.test(ua))              os = 'Android';
  else if (/\bWindows\b/.test(ua))              os = 'Windows';
  else if (/Mac OS X|Macintosh/.test(ua))       os = 'macOS';
  else if (/\bLinux\b/.test(ua))                os = 'Linux';

  // browser — order matters. All Chromium UAs include "Safari/", all
  // Edge UAs include "Chrome/", so the most specific token must win.
  let browser = 'other';
  if      (/\bEdg\//.test(ua))     browser = 'Edge';
  else if (/\bFirefox\//.test(ua)) browser = 'Firefox';
  else if (/\bChrome\//.test(ua))  browser = 'Chrome';
  else if (/\bSafari\//.test(ua))  browser = 'Safari';

  return { device_type, os, browser };
}