ASC LAST page adjustment Part 2 ver 3

// ==UserScript==
// @name            ASC adjust to last page on display of posts. Part #2
// @namespace       bubo-bubo/gmscripts
// @description     ASC - Add last page button on list pages
// @include         https://discussions.apple.com/message/*
// @include         https://discussions.apple.com/thread/*
// @include         https://discussions.apple.com/docs/*
// @version         4Apr2017
// @grant           none
// ==/UserScript==

/* We may not end up on the last page of a display of posts when Apple hosts
 deleted some posts.

 https://discussions.apple.com/docs/DOC-10241?start=45&tstart=0&begin=Prior-1
 https://discussions.apple.com/thread/5469616?start=1020&tstart=0&begin=yes

 How the input web address is contructed.
        constructedLink = "https://discussions.apple.com/thread/" +
                          postNumber +
                          "?start=" +
                          lastPageStart +
                          "&tstart=0&begin=yes";

 */

var debug                   = 2;  // 0 -- no debug
                                  // 1 -- normal debug
                                  // 2 -- intense debug


var aDate = new Date();
console.log ("--> adjustLastPage: add fast links Part #2. Debug is  " + debug +
             " on " + aDate );

// Setup once page is loaded.
if (debug)  console.log('Loaded; Now, initializing');


var url = window.location.href;
var params = url.split('?');

if (debug) console.log("web page parms " + params[1]);


// See if we have already adjusted this page.
    try
    {
      pageStatus = Window.asc_jx_last_page_load_remember;

     }// End of try
    catch(err)
    {
       console.log("looking for variable pageStatus " + err.message );
       //return;
    }
if (debug) console.log("pageStatus is " + pageStatus);


myPassVar = getURLParameter('begin').toLowerCase();
if (debug) console.log("begin parm is " + myPassVar);

if (debug) console.log("myPassVar.substr(0,6) " + myPassVar.substr(0,6));
// Do we need to see if we need to adjust to the last page?
if ( ( myPassVar == "yes"|| myPassVar == "last" || myPassVar.substr(0,6) == "prior-") && pageStatus != "yes")
  {
    // Global remember, so we can check if we already adjusted this page
    Window.asc_jx_last_page_load_remember = "yes";

    if (debug>= 2) console.log("Have set Window.asc_jx_last_page_load_remember to  " +
                           Window.asc_jx_last_page_load_remember);
    currentPageStart = getURLParameter('start');
    if (debug) console.log("start parm is " + currentPageStart);

    // Check what page we are on.
    var pageNumbers =  $("span.current-page").text();
    if (debug) console.log("pageNumbers " + pageNumbers);



    // Ejaz explans how to pull words from a string
    //   in  http://stackoverflow.com/questions/16223043/get-second-and-third-words-from-string
    // The technique using split() will fail if the string has multiple spaces in it.
    // Don't forget to check your array length using .length property to avoid
    //   getting undefined in your variables.
    var actualPages = pageNumbers.match(/\S+/gi);
    if (debug) console.log("closer "+ actualPages);

    var currentPage = parseInt(actualPages[1]);
    var lastPage = parseInt(actualPages[3]);
    if (debug) console.log("currentPage " + currentPage.toString() );
    if (debug) console.log("lastPage " + lastPage.toString() );

    if (myPassVar.substr(0,6) == "prior-")
    {
      /*
      <a href="/thread/7899185?start=90&amp;tstart=0"
      title="Select to go to last page"
      role="button"
      aria-label="Select to go to last page"
      onclick="jspaginate.init('last', '7'); return false;"
      class="js-pagination-next j-paginate-last">last</a>
      */
      var lastInfo = $("a.js-pagination-next.j-paginate-last")

      var lastHref = $(lastInfo).attr("href")
      if (debug>= 2) console.log("lastHref is " + lastHref);
      /* Find where the last page starts.  With this, we can figure out
         the post per page.
         lastHref is /thread/7899185?start=90&tstart=0
      */
      var pageStartCount = parseInt(lastHref.split("=")[1].split("&")[0].replace(/%2C/g, ''))
      if (debug>= 2) console.log("pageStartCount is " + pageStartCount);
      var itemsPerPage = pageStartCount/(lastPage-1)  // 15
      if (debug>= 2) console.log("itemsPerPage is " + itemsPerPage);
      var backPrior = parseInt(myPassVar.split("-")[1])
      if (debug>= 2) console.log("backPrior is " + backPrior);
      if (debug>= 2) console.log("(currentPage + backPrior)  " + (currentPage + backPrior));
      if ((currentPage + backPrior) !=  lastPage )
        {
          if (debug) console.log( "Need to adjust. lastPage(backPrior *itemsPerPage) is  "  +
                                ( (lastPage-backPrior-1) * itemsPerPage ) +
                                " currentPage is " +
                                 (lastPage-backPrior) );
          /* count of posts starts at zero whereas page count starts at 1 */
          jspaginate.update(
                           ( (lastPage-backPrior-1) * itemsPerPage ), // target
                           (lastPage-backPrior) // current
                          )
        }
      else
        {
          if (debug) console.log("on correct page which is " + currentPage);
        }

    } // Processing for prior
    else
    {
    // If the current page is differernt than the last page, apple removed some post
    // and we need to adjust to last page.
    if ( currentPage != lastPage )
      {
        if (debug) console.log("mismatched pages ");
        // Adjust to the last page.
        // Handy dandy ASC function is used when user clicks on last button, so use it
        jspaginate.init('last', actualPages[3]);
        if (debug) console.log("Page adjusted! " );
      }
    }
  }
else
  {
    if (debug) console.log("... Nothing to do! ...");
  }


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

// ----------------------------------------------------------------------------------------
//
// http://stackoverflow.com/questions/11582512/how-to-get-url-parameters-with-javascript
//
// example:
//   myvar = getURLParameter('myvar');

function getURLParameter(name) {
  return decodeURIComponent((new RegExp('[?|&]' + name + '=' + '([^&;]+?)(&|#|;|$)').exec(location.search) ||
                            [null, ''])[1].replace(/\+/g, '%20')) || null;
}