// ==UserScript==
    // @name         Amazon Search LibGen
    // @version      1.0.0
    // @description  It add amazon's books page a link in order to search on libGen Library Genesis the title, author o ISBN code of the viewed books
    // @author       Flejta
    // @match        https://www.amazon.com/*
    // @match        https://www.amazon.fr/*
    // @match        https://www.amazon.de/*
    // @match        https://www.amazon.co.uk/*
    // @match        https://www.amazon.it/*
    // @match        https://www.amazon.%2A/*
    // @grant        none
    // @namespace https://greasyfork.org/users/859328
    // ==/UserScript==

    (function() {
        'use strict';
        var BASEURL = "http://gen.lib.rus.ec/";

        function getAuthor() {
            var author = document.querySelector('span.author span a.contributorNameID')
                || document.querySelector('span.author a.a-link-normal')
                || document.getElementById('bylineContributor');
            return author.innerText.trim();
        }

        function getTitleElem() {
            return document.getElementById('productTitle')
                || document.getElementById('title')
                || document.getElementById('ebooksTitle');
        }

        function getTitle() {
            var title = getTitleElem();
            return title.innerText.match(new RegExp("([^(\[)]+)"))[0].trim();
        }

        function addLinkElem(id, elem) {
            document.getElementById(id).appendChild(elem);
        }

        function createLibgenDiv() {
            // outer div
            var outerDiv = document.createElement('div');
            outerDiv.className='a-size-base';


            if (document.getElementById('dp') && document.getElementById('dp').className.trim() == 'ebooks_mobile') {
                outerDiv.style.margin = '20px';
                document.getElementById('dp').insertBefore(outerDiv, document.getElementsByClassName('a-container')[0]);
            } else {
                outerDiv.style.margin="5px";
                var title = getTitleElem();
                title.parentNode.appendChild(outerDiv);
            }
            outerDiv.style.padding="5px";
            outerDiv.style.border = "2px solid rgb(128, 0, 0)";
            outerDiv.style.float = "right";

            // libgen div
            var libgenDiv = document.createElement('div');
            libgenDiv.id = 'libgen';
            var b = document.createElement('b'); b.innerText = 'LibGen (Sci-Tech): '
            b.style.float = "left";
            libgenDiv.appendChild(b);
            outerDiv.appendChild(libgenDiv);

            // fiction div
            var fictionDiv = document.createElement('div');
            fictionDiv.style.marginTop="2em";
            fictionDiv.id = 'fiction';
            var b2 = document.createElement('b'); b2.innerText = 'LibGen Fiction: '
            b2.style.float = "left";
            fictionDiv.appendChild(b2);
            outerDiv.appendChild(fictionDiv);
        }


        function createLink(href, text) {
            var container = document.createElement('div');
            container.style.float = "left";
            container.style.paddingLeft = "10px";
            var innerContainer = document.createElement('div');
            innerContainer.style.border = "1px solid rgb(127, 127, 127)";
            innerContainer.style.paddingLeft = "5px";
            innerContainer.style.paddingRight = "5px";
            var a = document.createElement('a');
            a.href = href;
            a.innerText = text;
            innerContainer.appendChild(a);
            container.appendChild(innerContainer);
            return container;
        }


        function addIsbnSearchLink(isbnType) {
            Array.from(document.querySelectorAll('span.a-text-bold'))
                .filter(elem => elem.innerText.indexOf(isbnType) != -1)
                .map(isbnTextElement => {
                var isbn = isbnTextElement.nextSibling.nextSibling.innerText.trim();
                var url = BASEURL + "search.php?req=" + isbn+ "&lg_topic=libgen&open=0&view=simple&res=25&phrase=1&column=identifier";
                addLinkElem('libgen', createLink(url, isbnType.toLowerCase()));
            });

            // ugly copy&paste for mobile support
            Array.from(document.getElementsByTagName('th'))
                .filter(elem => elem.innerText.indexOf(isbnType) != -1)
                .map(isbnTextElement => {
                var isbn = isbnTextElement.nextElementSibling.textContent.trim();
                var url = BASEURL + "search.php?req=" + isbn+ "&lg_topic=libgen&open=0&view=simple&res=25&phrase=1&column=identifier";
                addLinkElem('libgen', createLink(url, isbnType.toLowerCase()));
            });
        }

        function addLibgenSearchLink(searchString, linkText) {
            var url = BASEURL + "search.php?req=" + encodeURIComponent(searchString)
            + "&open=0&res=25&view=simple&phrase=1&column=def";
            addLinkElem('libgen', createLink(url, linkText))
        }

        function addFictionSearchLink(searchString, linkText) {
            var url = BASEURL + "fiction/?q=" + encodeURIComponent(searchString);
            addLinkElem('fiction', createLink(url, linkText))
        }

        createLibgenDiv();

        var author = getAuthor();
        var title = getTitle();

        if (author && title) {
            var searchString = author + ' ' + title;
            addLibgenSearchLink(searchString, "Author + Title");
            addFictionSearchLink(searchString, "Author + Title");
        }

        if (title) {
            addLibgenSearchLink(title, "Title");
            addFictionSearchLink(title, "Title");
        }

        if (author) {
            addLibgenSearchLink(author, "Author");
            addFictionSearchLink(author, "Author");
        }

        addIsbnSearchLink('ISBN-10');
        addIsbnSearchLink('ISBN-13');
    })();