// ==UserScript==
// @name         Arrow Keys: Next/Prev Chapter
// @namespace    https://greasyfork.org/users/45933
// @version      0.0.2
// @author       Fizzfaldt
// @description  Arrow Key Keyboard shortcuts for Multiple Sites (next/prev chapter)
// @run-at       document-end
// @grant        none
// @noframes
// @nocompat    Chrome
// @match        *://*.wuxiaworld.co/*
// @match        *://*.wuxiaworld.com/*
// @match        *://*.fanfiction.net/*
// @downloadURL none
// ==/UserScript==

/* jshint esversion: 6 */

function xPathResultToUniqueNode(x, context) {
    'use strict';
    if (!x) {
        alert("NULL xPathResult! " + context);
    }
    let first = x.iterateNext();
    if (!first) {
        alert("No xPathResult node! " + context);
        return;
    }
    let second = x.iterateNext();
    while (second != null && second.value == first.value) {
        second = x.iterateNext();
    }
    if (second != null && second.value != first.value) {
        alert("xPathResult had unique second node! [" + second + " ] " + context);
    }
    return first;
}

const prev = "prev";
const next = "next";

function getXpaths() {
    'use strict';

    var xpaths = {
        "wuxiaworld.co" : {
            prev : '//a[@class="prev" and @href]/@href',
            next : '//a[@class="next" and @href]/@href',
        },
        "wuxiaworld.com" : {
            prev : '//li[@class="prev"]/a[contains(@class, "btn-link") and @href]/@href',
            next : '//li[@class="next"]/a[contains(@class, "btn-link") and @href]/@href',
        },
        "fanfiction.net" : {
            prev : '//button[@class="btn" and contains(@onclick, "self.location=") and text()="< Prev"]/@onclick',
            next : '//button[@class="btn" and contains(@onclick, "self.location=") and text()="Next >"]/@onclick',
        },
    };

    var domain = location.hostname;
    while (domain != '') {
        if (domain in xpaths) {
            return xpaths[domain];
        }
        // Strip one subdomain and try again
        let temp = domain.split('.');
        temp.shift();
        domain = temp.join('.');
    }
    return null;
}

var pathsForHost = getXpaths();

function arrows(e) {
    'use strict';
    var result;
    switch (e.keyCode) {
        case 37: // Left
            result = document.evaluate(pathsForHost[prev], document, null, XPathResult.ANY_TYPE, null);
            break;
        case 39: // Right
            result = document.evaluate(pathsForHost[next], document, null, XPathResult.ANY_TYPE, null);
            break;
            // case 38: // Up
            // case 40: // Down
        default:
            return;
    }
    let linkHref = xPathResultToUniqueNode(result);
    let href = linkHref.value;
    // Handle location actually being javascript command
    href = href.replace(/^self.location='(.*)'$/, '$1');
    location.href=href;
}

if (pathsForHost) {
    document.addEventListener('keyup', arrows, false);
}