const fe = mip.nextElementSibling;
          if(fe) mip.parentNode.insertBefore(e, fe);
          else D.append(mip.parentNode, e);
        }else{
          D.append(holder,e);
          this.e.newestMessage = e;
        }
        if(!atEnd && !this.isBatchLoading
           && e.dataset.xfrom!==this.me && !isInViewport(e)){
          /* If a new non-history message arrives while the user is
             scrolled elsewhere, do not scroll to the latest
             message, but gently alert the user that a new message
             has arrived. */
          F.toast.message("New message has arrived.");
        }else if(!this.isBatchLoading && e.dataset.xfrom===Chat.me){
          this.scheduleScrollOfMsg(e);
        }else if(!this.isBatchLoading){
          /* When a message from someone else arrives, we have to
             figure out whether or not to scroll it into view. Ideally
             we'd just stuff it in the UI and let the flexbox layout
             DTRT, but Safari has expressed, in no uncertain terms,
             some disappointment with that approach, so we'll
             heuristicize it: if the previous last message is in view,
             assume the user is at or near the input element and

      */
      scrollMessagesTo: function(where){
        if(where<0){
          Chat.e.messagesWrapper.scrollTop = 0;
        }else if(where>0){
          Chat.e.messagesWrapper.scrollTop = Chat.e.messagesWrapper.scrollHeight;
        }else if(Chat.e.newestMessage){
          Chat.e.newestMessage.scrollIntoView(false);
        }
      },
      toggleChatOnlyMode: function(){
        return this.chatOnlyMode(!this.isChatOnlyMode());
      },
      settings:{
        get: (k,dflt)=>F.storage.get(k,dflt),

    const toolbar = Chat.e.loadOlderToolbar = D.attr(
      D.fieldset(loadLegend), "id", "load-msg-toolbar"
    );
    Chat.disableDuringAjax.push(toolbar);
    /* Loads the next n oldest messages, or all previous history if n is negative. */
    const loadOldMessages = function(n){
      Chat.ajaxStart();
      Chat.e.messagesWrapper.classList.add('loading');
      Chat.isBatchLoading = true;
      var gotMessages = false;
      fetch("chat-poll?before="+Chat.mnMsg+"&n="+n)
        .then(x=>x.json())
        .then(function(x){
          gotMessages = x.msgs.length;
          newcontent(x,true);
        })
        .catch(e=>Chat.reportError(e))
        .finally(function(){
          Chat.isBatchLoading = false;
          Chat.e.messagesWrapper.classList.remove('loading');
          if(n<0/*we asked for all history*/
             || 0===gotMessages/*we found no history*/
             || (n>0 && gotMessages<n /*we got fewer history entries than requested*/)
             || (false!==gotMessages && n===0 && gotMessages<Chat.loadMessageCount
                 /*we asked for default amount and got fewer than that.*/)){
            /* We've loaded all history. Permanently disable the
               history-load toolbar and keep it from being re-enabled
               via the ajaxStart()/ajaxEnd() mechanism... */
            const div = Chat.e.loadOlderToolbar.querySelector('div');
            D.append(D.clearElement(div), "All history has been loaded.");
            D.addClass(Chat.e.loadOlderToolbar, 'all-done');

    D.append(Chat.e.messagesWrapper, toolbar);
    toolbar.disabled = true /*will be enabled when msg load finishes */;
  })()/*end history loading widget setup*/;

  async function poll(isFirstCall){
    if(poll.running) return;
    poll.running = true;
    if(isFirstCall){
      Chat.ajaxStart();
      Chat.e.messagesWrapper.classList.add('loading');
    }
    Chat.isBatchLoading = isFirstCall;
    var p = fetch("chat-poll?name=" + Chat.mxMsg);
    p.then(x=>x.json())
      .then(y=>newcontent(y))
      .catch(e=>console.error(e))
    /* ^^^ we don't use Chat.reportError(e) here b/c the polling
       fails exepectedly when it times out, but is then immediately
       resumed, and reportError() produces a loud error message. */
      .finally(function(){
        if(isFirstCall){
          Chat.isBatchLoading = false;
          Chat.ajaxEnd();
          setTimeout(function(){
            Chat.scrollMessagesTo(1);
            Chat.e.messagesWrapper.classList.remove('loading');
          }, 250);
        }
        poll.running=false;
      });
  }
  poll.running = false;
  poll(true);
  setInterval(poll, 1000);
  F.page.chat = Chat/* enables testing the APIs via the dev tools */;
})();