(function(){
  function getSource(){
    try{
      let s=sessionStorage.getItem('ctb.src');
      if(s)return s;
      const p=new URLSearchParams(location.search);
      s=p.get('utm_source')||p.get('src')||'';
      if(!s&&document.referrer){try{const h=new URL(document.referrer).hostname;if(h&&h!==location.hostname)s=h}catch(e){}}
      s=s||'(direct)';
      sessionStorage.setItem('ctb.src',s);
      return s;
    }catch(e){return '(direct)'}
  }
  window.ctbGetSource=getSource;
  const path=location.pathname.replace(/\/$/,'')||'/';
  const page=path==='/'?'bridge':(path==='/start'?'start':null);
  if(page)fetch('/api/public/track',{method:'POST',headers:{'Content-Type':'application/json'},body:JSON.stringify({event:page,source:getSource()})}).catch(()=>{});
})();