// ==UserScript==
// @name         Next Chapter Shortcut
// @namespace    https://greasyfork.org/en/users/55535-sllypper
// @version      0.4
// @description  And insta-scrolling for Mangakakalot & Manganelo
// @author       sllypper
// @match        https://mangakakalot.com/chapter/*
// @match        https://manganelo.com/chapter/*
// @grant        none
// @downloadURL none
// ==/UserScript==

(function() {
    'use strict';

    let scrollAmount = 64;
    let repeatBy = 32;

    let scrollActions = {};

    let buttons = document.getElementsByClassName('navi-change-chapter-btn');
    if (buttons.length === 0) {
        buttons = document.getElementsByClassName('btn-navigation-chap');
        if (buttons.length === 0) return;
    }

    buttons = buttons[0].childNodes;

    let prevButton = buttons[0];
    let nextButton = buttons[buttons.length-1];

    // if there's only one button
    if (buttons.length != 2) {
        // if it's the "next" button
        if (buttons[0].classList.contains("next") || buttons[0].classList.contains("navi-change-chapter-btn-next")) {
            // then we're in chapter 1
            // and there's no prev button
            prevButton = null;
        } else {
            // else we're in the last chapter
            // and there's no next button
            nextButton = null;
        }
    }

    document.addEventListener("keydown", event => {
        if (event.code === "KeyW" || event.code === "KeyK") {
            if (scrollActions.up === undefined) {
                scrollAction(-scrollAmount, repeatBy, 'up');
            }
        } else if (event.code === "KeyS" || event.code === "KeyJ") {
            if (scrollActions.down === undefined) {
                scrollAction(scrollAmount, repeatBy, 'down');
            }
        } else if (event.code === "KeyC" && nextButton != null) {
            nextButton.click();
        } else if (event.code === "KeyZ" && prevButton != null) {
            prevButton.click();
        }
    });

    document.addEventListener("keyup", event => {
        if (event.code === "KeyW" || event.code === "KeyK") {
            clearScrollAction('up');
        } else if (event.code === "KeyS" || event.code === "KeyJ") {
            clearScrollAction('down');
        }
    });

    function scrollAction(amount, freq, id) {
        scrollActions[id] = setInterval(() => {
            window.scrollBy(0, amount);
        }, freq)
    }

    function clearScrollAction(id) {
        clearInterval(scrollActions[id]);
        scrollActions[id] = undefined;
    }

})();