/* ---------------- live events ---------------- */
let sse: EventSource;
/// The feed list and the open list, taken again from the server. The events keep both current,
/// and one missed is a count wrong until a reload: reading an item sends none to your other
/// pages, so one read on another device stayed unread here, and an iPhone stops the stream while
/// the app is in the background, when everything is missed (#168).
const catchUp=(()=>{ let t: number; return ()=>{ clearTimeout(t); t=setTimeout(()=>{
  loadFeeds(true).catch(()=>{});
  if(S.feed) loadEntries(false,true).catch(()=>{});
},300); }; })();
document.addEventListener('visibilitychange',()=>{ if(!document.hidden) catchUp(); });
let dropped=false;
function connect(){
  sse=new EventSource('/api/events');
  // Back after a drop: whatever was sent meanwhile went to nobody.
  sse.onopen=()=>{ if(dropped){ dropped=false; catchUp(); } };
  const soon=(fn: ()=>void,ms=500)=>{ let t: number; return ()=>{ clearTimeout(t); t=setTimeout(fn,ms); }; };
  // Caught: a network gone when one fires (a laptop asleep) was an unhandled rejection (#219).
  const refreshEntries=soon(()=>{ if(S.feed) loadEntries(false,true).catch(()=>{}); });
  // Every scan's events reach everyone; only this person's feeds are theirs to show or refresh.
  const mine=(id: string)=>S.feeds.some(f=>f.id===id);
  // The lists a change made stale, fetched again behind, once a burst of rows has passed (#247).
  const preloadSoon=soon(preloadLists,2000);
  sse.onmessage=m=>{
    let ev; try{ ev=JSON.parse(m.data) }catch{ return }
    if(ev.ev==='progress'){
      const pct=ev.total?ev.done/ev.total*100:0;
      // Only the row actually downloading. Without the enclosure id this used to paint
      // every pending bar at once, so adding a feed looked like it was fetching the lot.
      const bar=document.querySelector<HTMLElement>(`.dlbar[data-bar="${ev.enclosure}"] i`);
      if(bar){ bar.style.width=pct+'%'; bar.parentElement!.classList.add('live'); }
      $('#count') && ($('#count').textContent=`downloading ${ev.file} — ${pct.toFixed(0)}%`);
    }
    else if(ev.ev==='download_done'){
      const bar=document.querySelector(`.dlbar[data-bar="${ev.enclosure}"]`);
      // Said only for a file on screen, as one downloaded by hand is: the scheduled downloads of
      // everyone's feeds used to announce themselves to everyone.
      if(bar){ bar.classList.remove('live'); toast('Downloaded '+ev.path.split('/').pop()); }
      refreshEntries();
    }
    // A copy finished: the episode's "Cutting dead air…" becomes how much shorter it is.
    else if(ev.ev==='deadair_done'){
      if(!mine(ev.feed)) return;
      if(ev.saved_s>0&&document.querySelector('.dapend')) toast(`DeadAir is done: ${shorter(ev.saved_s)}`);
      refreshEntries();
      if(S.sel) loadEntries(false,true).then(()=>{ const e=cur(); if(e) showDetail(e); }).catch(()=>{});
    }
    else if(ev.ev==='download_error'){
      const bar=document.querySelector(`.dlbar[data-bar="${ev.enclosure}"]`);
      if(bar) bar.classList.remove('live');
      toast('Download failed: '+ev.msg,true); refreshEntries();
    }
    // A spinner on the feed's row while it is checked, in place of a toast per feed (issue #37).
    else if(ev.ev==='feed_start') setScanning(ev.feed,true);
    else if(ev.ev==='feed_skip') setScanning(ev.feed,false);
    else if(ev.ev==='feed_done'){
      setScanning(ev.feed,false);
      if(!mine(ev.feed)) return;
      if(ev.feed===S.feed||S.feed===':all') refreshEntries();
    }
    // No toast: a scan of every feed raised one per failure, to everyone. The feed list's
    // red ! marks the feed instead, and its page says why.
    else if(ev.ev==='feed_error') setScanning(ev.feed,false);
    // The server sends a feed's new row after anything changes it (counts, error, last check),
    // only to those who subscribe; the page used to reload the whole list after each event.
    else if(ev.ev==='feed_row'){ patchFeed(ev.row); forgetLists(ev.row.id); preloadSoon(); }
    // Only a scan that checked something: the scheduler scans every minute, due or not, and
    // every open page reloaded the whole list each time (#103).
    // Rows came as feed_row events. ponytail: a feed an OPML drops stays in the list until the
    // page reloads; reload the list here when a scan synced an OPML if that ever matters.
    else if(ev.ev==='scan_done'){ scanning.clear(); paintScanning(); spinEnd(ev); if(ev.feeds) refreshEntries(); }
    // The worker's job failed, so the scan someone is waiting on will send no scan_done.
    else if(ev.ev==='error') spinEnd();
  };
  sse.onerror=()=>{ sse.close(); dropped=true; setTimeout(connect,4000); };
}
connect();
loadFeeds().then(preloadLists).catch(()=>{});