var imagePath = '/images/';
var imageFiles = {
    'default':'preview-year-of-the-map.jpg',
    'nyc_cover':'preview_panamap_nyc_cover.jpg',
    'nyc_photo1':'preview_panamap_nyc_photo1.jpg',
    'nyc_photo2':'preview_panamap_nyc_photo2.jpg',
    'chicago_cover':'preview_panamap_chi_cover.jpg',
    'chicago_photo1':'preview_panamap_chi_photo1.jpg',
    'chicago_photo2':'preview_panamap_chi_photo2.jpg',
    'yearofthemap':'preview-year-of-the-map.jpg',
    'themapisback':'preview_themapisback.gif',
    'trophy':'preview_panamap_trophy.jpg',
};

function addEvents(ul_id) {
    links = document.getElementById(ul_id).getElementsByTagName('a');
    for (var i = 0; i < links.length; i++) {
        link = links[i];
        if ( link.hasAttribute('preview') ) {
            key = link.getAttribute('preview')
            link.setAttribute('onmouseover', "setPreview('" + key + "');");
            link.setAttribute('onmouseout', "setPreview('default');");
        }
    }
};

function preloadImages() {
    document.hiddenImages = {};
    var img = document.getElementById('preview').getElementsByTagName('img')[0];
    for (var i in imageFiles) {
        var newimg = document.createElement('img')
        newimg.setAttribute('src', imagePath + imageFiles[i]);
        document.hiddenImages[i] = newimg;
    }
}

function setPreview(key) {
    var div = document.getElementById('preview');
    var oldimg = div.getElementsByTagName('img')[0];
    var newimg = document.hiddenImages[key];
    oldimg.parentNode.replaceChild(newimg, oldimg);
}

function initPreview() {
    preloadImages();
    addEvents('links_nyc');
    addEvents('links_chi');
    addEvents('marketing_links');
}