/*!
 * Flexible Nav - 2011 - by @greweb
 */

// The code
// ========
//
(function($){
    "use strict";

    // **Utilities functions**
    //
    // Generate an unique number identifier
    var _uuid = 0;
    var uuid = function(){ return ++_uuid; };

    // Template for creating a nav element with links.
    //
    // * `links` : an Array of *{ href, text }*
    var tmplNav = function(links) {
        var nav = $('<nav class="flexible-nav"><ul></ul></nav>');
        var lis = $.map(links, function(link){
            return $('<li><a href="'+link.href+'">'+link.text+'</a></li>')[0];
        });
        nav.find('ul').append(lis);
        return nav;
    }


    // Retrieve a node pointed by an a element `aEl` hash href.
    var targetForLink = function(aEl) {
        var href = $(aEl).attr('href');
        if(href.substring(0,1) == '#') {
            var target = $(href);
            return target.size() ? target : null;
        }
        return null;
    }


    // FlexibleNavMaker
    // ------------------------
    // Dynamically create a nav.
    //
    // * `selector` (optional) : selector for all nodes to add in nav.
    // using `h1, h2, h3` if not setted.
    window.FlexibleNavMaker = function(selector) {
        var self = this;
        self.nodes = $(selector || 'h1,h2,h3');

        // ### .make() ###
        // An instance of FlexibleNavMaker contains only a `make` method
        // which create the nav element with nodes matching `selector`.
        self.make = function() {
            var links = self.nodes.map(function(){
                var node = $(this);
                // Find the id or create a unique one
                var id = node.attr('id');
                if(!id) {
                    while(!id) {
                        id = 'n'+( uuid() );
                        if($('#'+id).size()>0) id = null;
                    }
                    node.attr('id', id);
                }
                // The text link is the `data-navtext` attribute or the node text.
                var text = node.attr('data-navtext') || node.text();
                return { href: '#'+id, text: text };
            });
            return tmplNav(links);
        }
    }

    // FlexibleNav
    // -----------
    // Make a nav element "flexible".
    //
    // * `nav` : a nav DOM element
    window.FlexibleNav = function(nav) {
        var self = this;
        self.nav = $(nav);

        // Init links adding some classes.
        //
        // Set the target node name class.
        // Example: class `tnn-h1`
        self.updateClasses = function() {
            self.nav.find('a').each(function(){
                var node = $(this);
                var target = targetForLink(node);
                if(target) {
                    node.addClass('tnn-'+target[0].nodeName.toLowerCase());
                }
            });
        }

        // ### .update() ###
        self.update = function() {
            var documentHeight = $(document).height();
            var windowHeight = $(window).height();

            // Transform links into array of visible target `top` position and link `node`.
            var links = self.nav.find('a').map(function(){
                var node = $(this);
                var target = targetForLink(node);
                if (target==null || !target.is(':visible')) return null;
                return {
                    top: target.offset().top,
                    node: node
                };
            });

            // Update nav link positions.
            $.each(links, function(i, link) {
                link.node.css('top', (100*link.top/documentHeight)+'%');
            });

            // Update current section.
            var scrollTop = $(document).scrollTop();
            var closest = null;
            $.each(links, function(i, link){
                link.node.removeClass('current');
                if(closest==null || (link.top <= scrollTop+10 && link.top > closest.top))
                    closest = link;
            });
            closest && closest.node.addClass('current');
        }

        // ### Init ###
        // Bind scroll event and init nav.
        $(window).scroll(function(){
            self.update();
        });
        self.updateClasses();
        self.update();
    }
}(jQuery));