// ==UserScript==
// @name        Reddit Post Anchored Link
// @version     0.1.8
// @description Adds a button per post to represent an anchored link (like the parent button) derived from a permalink
// @license     MIT
// @author      Nguyen Duc My
// @namespace   https://github.com/hcpl
// @match       https://www.reddit.com/r/*/comments/*
// @grant       none
// ==/UserScript==


(function() {
    'use strict';

    addInitialPostLinkButtons();
    addDomObserversToMoreComments();
})();


function addInitialPostLinkButtons() {
    tryAddPostLinkButtons(document, 1);
}


function addDomObserversToMoreComments() {
    var moreComments = document.getElementsByClassName('morecomments');

    var observer = new MutationObserver(function(mutations, _observer) {
        for (var i = 0; i < mutations.length; ++i) {
            if (mutations[i].addedNodes.length && mutations[i].target.className.search('live-timestamp') < 0) {
                tryAddPostLinkButtons(mutations[i].target, 0);
            }
        }
    });

    for (var i = 0; i < moreComments.length; ++i) {
        var entryUnvoted = moreComments[i].parentElement;
        var thing = entryUnvoted.parentElement;
        var sideTable = thing.parentElement;

        observer.observe(sideTable, { childList: true, subtree: true });
    }
}


// Common

function tryAddPostLinkButtons(element, startIndex) {
    var buttonLists = element.getElementsByClassName('flat-list buttons');

    for (var i = startIndex; i < buttonLists.length; ++i) {
        var list = buttonLists[i];
        if (list.children.length >= 1 && list.getElementsByClassName('userscripted-button-list').length === 0) {
            var commentId = getCommentId(list);
            addButton(list, commentId);
        }
    }
}

function getCommentId(buttonList) {
    var a = buttonList.children[0].children[0];
    var pathParts = a.href.split('/');
    var commentId = pathParts[pathParts.length - 2];

    return commentId;
}

function addButton(buttonList, commentId) {
    var a = document.createElement('a');
    a.setAttribute('class', 'bylink userscripted-button-list');
    a.setAttribute('href', '#' + commentId);
    a.setAttribute('rel', 'nofollow');
    a.textContent = 'link';

    var li = document.createElement('li');
    li.appendChild(a);

    buttonList.appendChild(li);
}