/* ---------------- 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(); checkVersion(); flushOutbox(); } };
  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 }
    // Someone else's download is theirs: its file's name and its failure stay off this page (#294).
    if((ev.ev==='progress'||ev.ev==='download_error')&&!mine(ev.feed)) 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()); }
      // On iPX now, in what this page holds too, so the open file's box says so at once rather
      // than after the list comes again; and, asked for on this device, its copy here follows (#457).
      for(const e of S.entries) for(const x of e.enclosures) if(x.id===ev.enclosure){ x.path=ev.path; x.state='done'; }
      if(wanted.has(ev.enclosure)) followWanted({id: ev.enclosure, path: ev.path});
      else syncKeepButtons();
      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');
      unwant(ev.enclosure);
      // Which item, and what to do: the reason (ev.msg) is in the daemon's log (#304).
      const e=S.entries.find(x=>x.enclosures.some(n=>n.id===ev.enclosure));
      toast(`Unable to download ${e?`"${entryName(e).text}"`:'a file'}. Try again with its download button.`,true); refreshEntries();
    }
    // Jev picked items out for someone's Signals: theirs are fetched again, and the one open.
    else if(ev.ev==='signal_hits'){
      if(!S.signals.length) return;
      refreshSignals();
      if(signalOf(S.feed)) 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'||S.feeds.some(f=>f.id===ev.feed&&f.group===S.feed)) 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); };
}

/// A deploy of ipx-web drops the stream and the page kept running the script it loaded, in an
/// open tab or the home-screen app, until reloaded by hand (#388). Back after a drop, the page
/// asks for itself again: a different app.js named there is a new version.
const runningScript=document.querySelector('script[src^="/app.js"]')?.getAttribute('src');
async function checkVersion(){
  if(!runningScript) return;
  let page: string;
  // Mid-deploy, / can be a 502 or the sign-in page: no script named, nothing to compare.
  try{ const r=await fetch('/',{cache:'no-store'}); if(!r.ok) return; page=await r.text(); }catch{ return; }
  const live=page.match(/\/app\.js\?v=[0-9a-f]+/)?.[0];
  if(!live||live===runningScript) return;
  if(reloadWouldLose()) offerReload();
  else reloadKeepingPlace();
}
/// Something a reload throws away: an episode playing, a dialog open, a search or a field typed in.
function reloadWouldLose(){
  const typing=document.activeElement instanceof HTMLTextAreaElement
    || (document.activeElement instanceof HTMLInputElement && document.activeElement.type!=='range'
        && document.activeElement.type!=='checkbox' && document.activeElement.value!=='');
  return !audio.paused || !!$('#modal')?.classList.contains('on') || !!S.q || typing;
}
/// The feed and tab come back from localStorage; the item open is carried across in the session,
/// whole: read, it is off the Unread list the server sends after the reload.
function reloadKeepingPlace(){
  try{ const e=cur(); if(e) sessionStorage.setItem('ipx.reopen',JSON.stringify(e)); }catch{}
  location.reload();
}
/// The item open before a reload for a new version, once, for showList to open again.
function takeReopen(): Entry|null{
  try{
    const j=sessionStorage.getItem('ipx.reopen'); sessionStorage.removeItem('ipx.reopen');
    return j ? JSON.parse(j) as Entry : null;
  }catch{ return null; }
}
let offered=false;
function offerReload(){
  if(offered) return;
  offered=true;
  const t=document.createElement('div'), b=document.createElement('button');
  t.className='toast'; t.setAttribute('role','status'); t.textContent='A new version of iPX is ready. ';
  b.type='button'; b.className='btn'; b.textContent='Reload';
  b.onclick=reloadKeepingPlace;
  t.appendChild(b);
  $('#toasts')?.appendChild(t);
}
connect();
loadFeeds().then(preloadLists).catch(()=>{});