Link to last page in list pages

// ==UserScript==
// @name            ASC Display links to last page on all pages of discussion.
// @namespace       bubo-bubo/gmscripts
// @description     ASC - Add last page button on list pages
// @include     https://discussions.apple.com/content?*
// @include     https://discussions.apple.com/community/*/content?*
// @version     1
// @grant       none
// ==/UserScript==

// Uses Hiroto's event handler design.

/*
   Add link to last page of long discussions.

Supported lists:
  https://discussions.apple.com/content?filterID=following~objecttype~objecttype[thread]
  https://discussions.apple.com/community/ipad/ipad_in_business_and_education/content?filterID=contentstatus
    %5Bpublished%5D%7Eobjecttype%7Eobjecttype%5Bthread%5D
  https://discussions.apple.com/community/mac_os/os_x_el_capitan/content?filterID=contentstatus[published]
    ~objecttype~objecttype[thread]

but not:
  https://discussions.apple.com/community/lounge/full_host_bar


Why does apple slow down old devices?            66 18035   February 2, 2017 9:15 PM
in Using iPad by gail from maine                 by gail from maine

  https://discussions.apple.com/thread/7527129
  https://discussions.apple.com/thread/7527129?start=15&tstart=0
  https://discussions.apple.com/thread/7527129?start=30&tstart=0
  https://discussions.apple.com/thread/7527129?start=45&tstart=0
  https://discussions.apple.com/thread/7527129?start=60&tstart=0

https://discussions.apple.com/community/mac_os/os_x_yosemite/content?filterID=contentstatus%5Bpublished%5D~objecttype~objecttype%5Bthread%5D*/


var watchdog1, watchdog2;
var watchInterval           = 500; // [ms] Waiting for the user to change page
var shortWatchInterval      = 100; // [ms] Waiting for the system to load new list
var debug                   = 0;  // 0 -- no debug
                                  // 1 -- normal debug
                                  // 2 -- intense debug
var priorLastThread         = '';

var aDate = new Date();
console.log ("--> lastReadPageButton: add fast links. Debug is  " + debug +
             " on " + aDate );

// Setup once page is loaded.
// modify thread content view behaviour (in post-load phase)

 if (debug)  console.log('Loaded; Now, initializing');
 // register event listeners
 window.addEventListener('unload', function(e)
        {
          if (debug)  console.log('unloading.');
          stopWatchDogButton(watchdog1);
          stopWatchDogButton(watchdog2);

          window.removeEventListener('locationChangeButton',
                                      locationChangeButtonHandler,
                                      true);
          window.removeEventListener('waitingInsertLastPageAnchor',
                                      insertLastPageAnchor,
                                      true);
          if (debug)  console.log('removing e.type is '+ e.type + " arg is " +
                                  arguments.callee);
          // remove anonymous unload. [ Thus unload ]
          window.removeEventListener(e.type,
                                     arguments.callee,
                                     true);
        }, true);

 if (debug)  console.log('adding locationChangeButton event listner');
 window.addEventListener('locationChangeButton',
                         locationChangeButtonHandler,
                         true);
 window.addEventListener('waitingInsertLastPageAnchor',
                         insertLastPageAnchor,
                         true);
 // Engage a watch dog
 var prev_href = '';
 if (debug)  console.log('prev_href is ' + prev_href );
 // Spin around here watching for the web address to change.
 // Always spinning here.
 // It takes awhile after the page address changes before the list is loaded
 // so we don't need to check that often.
 watchdog1 = setInterval( function()
        {
          var curr_href = window.location.href;
          if (debug >= 2)  console.log('   prev_href is ' + prev_href +
                                 "\n     curr_href is " + curr_href);
          if (curr_href != prev_href)
            {
              // Page changed
              if (debug)  console.log('---> found new page. ' +
                                      '  curr_href is ' + curr_href +
                                      '  Dispatching short event.');
              window.dispatchEvent(new Event('locationChangeButton'));
              prev_href = curr_href;
            }
         },
         watchInterval); // end of setting watch dog #1


// -----------------------------------------------------------------------------
function locationChangeButtonHandler(e)
       {
         if (debug)  console.log('---> locationChangeButtonHandler is observed. '+
                                 "Debug is  " + debug);
         // Give a little time for the page to settle down.
         // Spin around here watching for the web address in the last entry to change.
         // Stop spinning once change is found
         watchdog2 = setInterval( function()
                {
                  var trSectionSpin = new Array();

                  trSectionSpin = $("table tr.js-browse-item td.j-td-title");
                  if (debug>=2) console.log("finding title" );
                  // .size() is in Jquery and other many other lib
                  rememberLastThread = $("a:first",
                                          trSectionSpin[trSectionSpin.size()-1]
                                        ).attr("href");
                  if (debug) console.log("last thread on page is " + rememberLastThread);
                  if (priorLastThread != rememberLastThread)
                    {
                      // Page changed
                      if (debug)  console.log('---> found new page: ' +
                                              rememberLastThread + ' Dispatching ' +
                                              'insert anchors event.');
                      window.dispatchEvent(new Event('waitingInsertLastPageAnchor'));
                      priorLastThread = rememberLastThread;
                      stopWatchDogButton(watchdog2);
                    }
                },
                   shortWatchInterval); // end of setting watch dog

        }

// -----------------------------------------------------------------------------
function stopWatchDogButton(dog) {
    clearInterval(dog);
    if (debug) console.log('Cleared interval for : ' + dog);
}

// -----------------------------------------------------------------------------
var replyCounts = new Array();
var titleCounts = new Array();
var done = 0;
var entrySize = 15;  // number of discussion listed on web page
var lastPageStart = 0;
var constructedLink = "";
var insertA = "";
var rememberLastThread = "";
var debugStop = 0;

function insertLastPageAnchor()
  {
   /* debugStop++;
    if ( debugStop > 5 ) throw new Error();*/

    if (debug) console.log('\nInserting last page anchors');/**/
    try
    {
      $("table tr.js-browse-item td.j-td-replies").each(
        function( index )
          {
            replyCounts[index] = $( this ).text();
            console.log("index is " + index );
            if (debug>=2) console.log("reply index is " + index +
                                      " for " + $( this ).text() );
          }
       ); // End of each
      }
    catch(err)
    {
       console.log("within insertLastPageAnchor got error of " + err.message );
       return;
    }

    console.log("here...");
    if (debug) for ( i = 0;i<replyCounts.length;++i )
      {
        console.log("reply " + i + " is " + replyCounts[i] );
      }

    if (debug) console.log("Find the titles");
    var trSection = new Array();
    trSection = $("table tr.js-browse-item td.j-td-title");
    $("a:first", trSection ).each(
      function( index )
        {
          titleCounts[index] = $( this ).text();
          if (debug) console.log("------  " + $( this ).html() + " ------");

          postNumber = $( this ).attr("href").split("/")[2].trim();
          if (debug) console.log("a post number is " + postNumber);

          mathFloorInt = Math.floor(replyCounts[index]/entrySize);
          console.log ("repies = " + replyCounts[index] + " mathFloorInt is " +
                       mathFloorInt );
          if (mathFloorInt)
          {
            lastPageStart = mathFloorInt * entrySize;
            constructedLink = "https://discussions.apple.com/thread/" +
                          postNumber +
                          "?start=" +
                          lastPageStart +
                          "&tstart=0";
             if (debug) console.log("link is " + constructedLink);

             insertA = '<span class="rcUserASCModLastReadPage">' +
                       '<a style=" color: SlateBlue; ' +
                       'margin-left: 15px; border: 1px dotted black;" ' +
                       'href="' +
                       constructedLink +
                       '">Last Page</a>' +
                       '</span>';
             if (debug) console.log("inserted is " + insertA);
             $( this ).after( insertA );
           }
        } // end of anonymous function
     ); // end of .each


  } // end of function insertLastPageAnchor

// Seems that javascript [ or someone ]
// sends the last value from an assignment statement as the return code to the caller.
done = 0;