index.js

'use strict';

var defaultOptions = {
    tocRegexp: /@\[toc\]/im,
    tocTitle: 'Table of Contents',
    tocId: 'toc',
    tocWrapperClass: 'toc',
    tocLevelWrapperClass: 'toc-level',
    anchorIdPrefix: 'h-',
    reverseLink: false
};

module.exports = function (md, options) {

    // Set default options
    var options = Object.assign({}, defaultOptions, options);

    // Global variables
    var headingInfos = [];

    md.inline.ruler.after('emphasis', 'toc', function (state, silent) {

        if (silent) {
            return false;
        }

        var match = options.tocRegexp.exec(state.src);
        match = !match ? [] : match.filter(function (m) {
            return m;
        });
        if (match.length < 1) {
            return false;
        }

        var token;

        token = state.push("toc_open", "toc", 1);
        token.markup = match[0];
        token = state.push("toc_body", "", 0);
        token = state.push("toc_close", "toc", -1);

        // to continue pasing, Update pos
        state.pos = state.pos + match[0].length;
        return true;
    });

    md.core.ruler.push('init_toc', function (state) {

        // For each rendering, initialize heading count
        var headingCounts = [null, 0, 0, 0, 0, 0, 0];
        var tokens = state.tokens;

        // Parses all heading information to render the TOC
        for (var i = 0; i < tokens.length; i++)
            if (tokens[i].type === 'heading_open') {
                var tagLevel = parseInt(tokens[i].tag[1]);
                var numbering = [];

                headingCounts[tagLevel] += 1;

                for (var j = 1; j < headingCounts.length; j++) {
                    if (j <= tagLevel) {
                        numbering.push(headingCounts[j]);
                    } else {
                        headingCounts[j] = 0;
                    }
                }

                var hInfo = {
                    numbering: numbering,
                    content: tokens[i + 1].content
                };

                headingInfos.push(hInfo);
            }
    });

    md.renderer.rules.toc_open = function (tokens, index) {
        return '<div id="' + options.tocId + '" class="' + options.tocWrapperClass + '"><h3>' + options.tocTitle + '</h3>';
    }

    md.renderer.rules.toc_close = function (token, index) {
        return '</div>';
    }

    md.renderer.rules.toc_body = function (tokens, index) {
        var results = [];
        var previousLevel = 0;

        for (var i = 0; i < headingInfos.length; i++) {
            var hInfo = headingInfos[i];
            var levelDiff = hInfo.numbering.length - previousLevel;

            if (levelDiff > 0) {
                for (var _ = 0; _ < levelDiff; _++) {
                    results.push('<ul class="' + options.tocLevelWrapperClass + '">');
                }
            } else if (levelDiff < 0) {
                for (var _ = 0; _ > levelDiff; _--) {
                    results.push('</ul>');
                }
            }

            var numberingStr = hInfo.numbering.join('.');
            var anchor = options.anchorIdPrefix + numberingStr;

            results.push('<li><a href="#' + anchor + '">' + numberingStr + '.</a> ' + hInfo.content + '</li>');

            previousLevel = headingInfos[i].numbering.length;
        }

        // Add the remaining </ul> tags at end of TOC.
        for (var i = 0; i < previousLevel; i++) {
            results.push('</ul>');
        }

        return results.join('');
    }

    md.renderer.rules.heading_open = function (tokens, index) {
        var hInfo = headingInfos.shift();
        var numberingStr = hInfo.numbering.join('.');
        var anchor = options.anchorIdPrefix + numberingStr;

        return '<' + tokens[index].tag + '><a href="#' + (options.reverseLink ? options.tocId : anchor) + '" id="' + anchor + '">' + numberingStr + '.</a> ';
    }
}