(function($){

$.fn.toc = function(options) {
    var defaults = {
            noBackToTopLinks: false,
            title: '',
            minimumHeaders: 3,
            headers: 'h1, h2, h3, h4, h5, h6',
            listType: 'ul', // values: [ol|ul]
            showEffect: 'none', // values: [show|slideDown|fadeIn|none]
            showSpeed: '0', // set to 0 to deactivate effect
            classes: { list: 'section table-of-contents',
                item: 'active'
            }
        },
        settings = $.extend(defaults, options);

    function fixedEncodeURIComponent (str) {
        return encodeURIComponent(str).replace(/[!'()*]/g, function(c) {
            return '%' + c.charCodeAt(0).toString(16);
        });
    }

    function createLink (header) {
        var innerText = (header.textContent === undefined) ? header.innerText : header.textContent;
        return "<a href='#" + fixedEncodeURIComponent(header.id) + "'>" + innerText + "</a>";
    }

    var headers = $(settings.headers).filter(function() {
        // get all headers with an ID
        var previousSiblingName = $(this).prev().attr( "name" );
        if (!this.id && previousSiblingName) {
            this.id = $(this).attr( "id", previousSiblingName.replace(/\./g, "-") );
        }
        return this.id;
    }), output = $(this);
    if (!headers.length || headers.length < settings.minimumHeaders || !output.length) {
        $(this).hide();
        return;
    }

    if (0 === settings.showSpeed) {
        settings.showEffect = 'none';
    }

    var render = {
        show: function() { output.hide().html(html).show(settings.showSpeed); },
        slideDown: function() { output.hide().html(html).slideDown(settings.showSpeed); },
        fadeIn: function() { output.hide().html(html).fadeIn(settings.showSpeed); },
        none: function() { output.html(html); }
    };

    var get_level = function(ele) { return parseInt(ele.nodeName.replace("H", ""), 10); };
    var highest_level = headers.map(function(_, ele) { return get_level(ele); }).get().sort()[0];
    var return_to_top = '<i class="icon-arrow-up back-to-top"> </i>';

    var level = get_level(headers[0]),
        this_level,
        html = settings.title + " <" +settings.listType + " class=\"" + settings.classes.list +"\">";
    headers.on('click', function() {
        if (!settings.noBackToTopLinks) {
            window.location.hash = this.id;
        }
    })
        .addClass('clickable-header')
        .each(function(_, header) {
            this_level = get_level(header);
            if (!settings.noBackToTopLinks && this_level === highest_level) {
                $(header).addClass('top-level-header').after(return_to_top);
            }
            if (this_level === level) // same level as before; same indenting
                html += "<li class=\"" + settings.classes.item + "\">" + createLink(header);
            else if (this_level <= level){ // higher level than before; end parent ol
                for(var i = this_level; i < level; i++) {
                    html += "</li></"+settings.listType+">"
                }
                html += "<li class=\"" + settings.classes.item + "\">" + createLink(header);
            }
            else if (this_level > level) { // lower level than before; expand the previous to contain a ol
                for(i = this_level; i > level; i--) {
                    html += "<" + settings.listType + " class=\"" + settings.classes.list +"\">" +
                        "<li class=\"" + settings.classes.item + "\">"
                }
                html += createLink(header);
            }
            level = this_level; // update for the next one
        });
    html += "</"+settings.listType+">";
    if (!settings.noBackToTopLinks) {
        $(document).on('click', '.back-to-top', function() {
            $(window).scrollTop(0);
            window.location.hash = '';
        });
    }

    render[settings.showEffect]();
};

})(jQuery);