リストの表示モードに対応した。

sumally-add-via-link.user.js

// ==UserScript==
// @name           sumally-add-via-link
// @namespace      swdyh
// @version        0.0.2
// @description    http://swdyh.tumblr.com/post/28474643309/sumally
// @include        http://sumally.com/*
// @exclude        http://sumally.com/p/*
// @run-at         document-end
// ==/UserScript==

/* User Script info
date: 2012-08-02T10:11:32.782+9:00
confirmed:
    Windows 7 Home Premium SP1 64bit:
        Firefox 14.0.1
        Google Chrome 21.0.1180.60
*/

/*jslint browser: true, maxlen: 80*/
// Edition 2012-07-27

(function executeAddViaLink(each, win, doc) {
    'use strict';

    var listArea, range, selector, addVia, eachAddedNodes, recordsReader, MO;

    listArea = doc.querySelector('.listLiquidArea, .listLineArea');

    if (!listArea) {
        return;
    }

    doc.head.appendChild(doc.createElement('style')).textContent = [
        'a.via {',
        '  color: #F8A41A !important;',
        '  margin-left: 5px !important;',
        '}',
        '.name > a.via[target] {',
        '  margin-left: 0 !important;',
        '}'
    ].join('\n');

    range = doc.createRange();
    selector = [
        '.text a[href^="http://sumally.com/p/"]',
        '.name > a.p[href^="http://sumally.com/p/"]'
    ].join(',');

    addVia = function addVia(node) {
        var nodeClassList, itemLink;

        nodeClassList = node.classList;

        if (
            !(
                nodeClassList && (
                    nodeClassList.contains('oneblock') ||
                        nodeClassList.contains('recoTimeline')
                )
            )
        ) {
            return;
        }

        itemLink = node.querySelector(selector);

        if (!(itemLink && !node.querySelector('.via'))) {
            return;
        }

        itemLink.parentNode.insertAdjacentHTML(
            'BeforeEnd',
            '<a class="via" data-item-url="' + itemLink.href + '">via</a>'
        );
    };

    each.call(doc.querySelectorAll('.oneblock, .recoTimeline'), addVia);

    range.selectNodeContents(doc.body);

    listArea.addEventListener('mouseover', function getItemPage(evt) {
        var via, createViaLink, xhr;

        via = evt.target;

        if (!(via.className === 'via' && !via.target)) {
            return;
        }

        createViaLink = function createViaLink(evt) {
            var xhr, itemPage, viaLink, viaURL, viaTitle, text;

            xhr = evt.target;

            if (!/^(?:200|304)$/.test(xhr.status)) {
                via.textContent = 'loading error';

                return;
            }

            itemPage = range.createContextualFragment(xhr.responseText);
            viaLink = itemPage.querySelector('a[data-gaq="product_via_link"]');

            if (!viaLink) {
                via.parentNode.removeChild(via);

                return;
            }

            viaURL = viaLink.href;
            viaTitle = viaLink.textContent;

            text = viaURL.length > 30 ? (viaURL.slice(0, 30) + '...') : viaURL;

            if (viaURL === viaTitle) {
                via.textContent = text;
            } else {
                via.textContent = viaTitle + ' ' + text;
            }

            via.href = viaURL;
            via.target = '_blank';

            via.insertAdjacentHTML('BeforeBegin', '<br>');
        };

        via.textContent = '...';

        xhr = new XMLHttpRequest();

        xhr.addEventListener('load', createViaLink);
        xhr.addEventListener('error', createViaLink);

        xhr.open('GET', via.dataset.itemUrl);
        // 何故かFirefox 14.0.1で動かない
        // xhr.responseType = 'document';
        xhr.send(null);
    });

    eachAddedNodes = function eachAddedNodes(record) {
        each.call(record.addedNodes, addVia);
    };
    recordsReader = function recordsReader(callback) {
        return function eachRecords(records) {
            records.forEach(callback);
        };
    };

    MO = win.MutationObserver || win.WebKitMutationObserver;

    new MO(recordsReader(eachAddedNodes)).observe(
        listArea,
        {childList: true, subtree: true}
    );
}(Array.prototype.forEach, window, document));