Elakiri Pagination Support UserScript

// ==UserScript==
// @name Elakiri Pagination Support
// @namespace net.hopefullysafe
// @match http://elakiri.com/
// @match https://elakiri.com/
// @match http://www.elakiri.com/
// @match https://www.elakiri.com/
// @require https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js
// @grant none
// ==/UserScript==

this.$ = this.jQuery = jQuery.noConflict(true);
$(document).ready(function() {

  function addBasic(spanElem, url, params, lastPageNo) {
    params.set('pp', 20);
    params.set('page', 1);
    spanElem
      .append("  [")
      .append($("<a/>", {
          html: "1-20",
          "class": "linkStyles",
          href: url.href
      }));

    if (lastPageNo > 2) {
      params.set('page', 2);
      spanElem
        .append(" ")
        .append($("<a/>", {
            html: "21-40",
            "class": "linkStyles",
            href: url.href
        }));

      params.set('pp', 40);
      params.set('page', 1);
      spanElem
        .append(" ")
        .append($("<a/>", {
            html: "1-40",
            "class": "linkStyles",
            href: url.href
        }));
    }

    spanElem
      .append("]");
  }

  function addMultiple20(spanElem, url, params, lastPageNo) {
    var longPages20 = Math.floor(lastPageNo / 2);    // for pp=20 and default_page_size=10
    if ( lastPageNo % 2 != 0) {
      longPages20++;
    }
    params.set('pp', 20);

    params.set('page', 1);
    spanElem
      .append($("<a/>", {
          html: "1-20",
          "class": "linkStyles",
          href: url.href
      }));

    params.set('page', 2);
    spanElem
      .append(" ")
      .append($("<a/>", {
          html: "21-40",
          "class": "linkStyles",
          href: url.href
      }));

    params.set('page', 3);
    spanElem
      .append(" ")
      .append($("<a/>", {
          html: "41-60",
          "class": "linkStyles",
          href: url.href
      }));

    if (longPages20 > 3) {
      spanElem
        .append(" ...");

      if (longPages20 >= 6) {
        params.set('page', longPages20 - 2);
        spanElem
          .append(" ")
          .append($("<a/>", {
              html: ((longPages20 - 2) * 20 - 19) + "-" + ((longPages20 - 2) * 20),
              "class": "linkStyles",
              href: url.href
          }));
      }
      if (longPages20 >= 5) {
        params.set('page', longPages20 - 1);
        spanElem
          .append(" ")
          .append($("<a/>", {
              html: ((longPages20 - 1) * 20 - 19) + "-" + ((longPages20 - 1) * 20),
              "class": "linkStyles",
              href: url.href
          }));
      }
      if (longPages20 >= 4) {
        params.set('page', longPages20);
        spanElem
          .append(" ")
          .append($("<a/>", {
              html: (longPages20 * 20 - 19) + "-" + (longPages20 * 20),
              "class": "linkStyles",
              href: url.href
          }));
      }
    }
  }

  function addMultiple40(spanElem, url, params, lastPageNo) {
    var longPages40 = Math.floor(lastPageNo / 4);    // for pp=40 and default_page_size=10
    if ( lastPageNo % 4 != 0) {
      longPages40++;
    }
    params.set('pp', 40);

    params.set('page', 1);
    spanElem
      .append($("<a/>", {
          html: "1-40",
          "class": "linkStyles",
          href: url.href
      }));

    if (longPages40 > 1) {
      params.set('page', 2);
      spanElem
        .append(" ")
        .append($("<a/>", {
            html: "41-80",
            "class": "linkStyles",
            href: url.href
        }));
    }
    if (longPages40 > 2) {
      params.set('page', 3);
      spanElem
        .append(" ")
        .append($("<a/>", {
            html: "81-120",
            "class": "linkStyles",
            href: url.href
        }));
    }
    if (longPages40 > 3) {
      spanElem
        .append(" ...");

      if (longPages40 >= 6) {
        params.set('page', longPages40 - 2);
        spanElem
          .append(" ")
          .append($("<a/>", {
              html: ((longPages40 - 2) * 40 - 39) + "-" + ((longPages40 - 2) * 40),
              "class": "linkStyles",
              href: url.href
          }));
      }
      if (longPages40 >= 5) {
        params.set('page', longPages40 - 1);
        spanElem
          .append(" ")
          .append($("<a/>", {
              html: ((longPages40 - 1) * 40 - 39) + "-" + ((longPages40 - 1) * 40),
              "class": "linkStyles",
              href: url.href
          }));
      }
      if (longPages40 >= 4) {
        params.set('page', longPages40);
        spanElem
          .append(" ")
          .append($("<a/>", {
              html: (longPages40 * 40 - 39) + "-" + (longPages40 * 40),
              "class": "linkStyles",
              href: url.href
          }));
      }
    }
  }

  $('<style>.linkStyles { font-size: .9em; }</style>').appendTo('body');

  $('#collapseobj_module_31 td:nth-child(2)').each(function(){
    var pageSpan = $(this).find("span.smallfont");
    var lastLink = $(pageSpan).find("a:last");
    if ($(lastLink).length) {

      var lastPageUrl = new URL($(lastLink).prop('href'));
      let params = lastPageUrl.searchParams;

      var lastPageNo = params.get('page');
      if (lastPageNo <= 4) {
        addBasic(pageSpan, lastPageUrl, params, lastPageNo);
      } else {
        pageSpan.append("<br/>").append("[");
        addMultiple20(pageSpan, lastPageUrl, params, lastPageNo);
        pageSpan.append(" / ");
        addMultiple40(pageSpan, lastPageUrl, params, lastPageNo);
        pageSpan.append("]");
      }
    }
  });
});