// ==UserScript==
// @name         Random button for e-hentai
// @namespace    uareader_random_button
// @version      1.2
// @description  *fap* *fap* *fap*
// @author       uareader
// @match        https://e-hentai.org/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    var buttonRandom;
    var galleries = document.getElementsByClassName("gl1t");
    var galleriesLength = galleries.length;
    var galleriesContainer;

    // create a button
    if(galleriesLength > 1) {

        let buttonRandom_insertion_area = document.querySelector("form[action='" + window.location.origin + window.location.pathname + "']");

        if(buttonRandom_insertion_area != null) {

            buttonRandom_insertion_area = buttonRandom_insertion_area.parentElement;

            buttonRandom = document.createElement("input");
            buttonRandom.value = "Randomize";
            buttonRandom.type = "button";
            buttonRandom.addEventListener('click',randomizeSearchResults,false);

            buttonRandom_insertion_area.appendChild(document.createElement("br"));
            buttonRandom_insertion_area.appendChild(buttonRandom);

            galleriesContainer = galleries[0].parentElement;

        }

    }

    // function that randomize the galleries results
    function randomizeSearchResults(click_event) {

        buttonRandom.removeEventListener('click',randomizeSearchResults,false);

        var indexesList = [];
        var tempValue;
        var randomIndex;

        // create an array of indexes
        for(let i = 0; i < galleriesLength; i++) {
            indexesList.push(i);
        }

        // swap each index with another from after within the array
        for(let i= 0; i < galleriesLength - 1; i++) {

            tempValue = indexesList[i];
            randomIndex = Math.floor(Math.random() * (galleriesLength - (i+1)) + (i+1));

            indexesList[i] = indexesList[randomIndex];
            indexesList[randomIndex] = tempValue;

        }

        // swap the last index with another from before within the array
        tempValue = indexesList[galleriesLength-1];
        randomIndex = Math.floor(Math.random() * (galleriesLength-1));

        indexesList[galleriesLength-1] = indexesList[randomIndex];
        indexesList[randomIndex] = tempValue;

        // finally randomize the galleries
        for(let i= 0; i < galleriesLength; i++) {
            galleriesContainer.insertBefore(galleriesContainer.childNodes[i], galleriesContainer.childNodes[indexesList[i]]);
        }

        buttonRandom.addEventListener('click',randomizeSearchResults,false);

    }

})();