/**
 * JS for the "request info" form.
 * 
 * 
 */

/**
 * Runs on page load.
 * 
 * 
 */
$(document).ready(function() {
    $('#source_1').bind('change', source1Onchange);
});

/**
 * Onchange handler for the "source_1" <select> element. Retrieves source_2
 * values from the server via Ajax.
 * 
 * 
 */
function source1Onchange(event) {
    var source_1 = $(this)[0].options[$(this)[0].selectedIndex].value;
    $.ajax({
        url: 'about/get_source_2_as_xml',
        type: 'POST',
        data: 'source_1=' + source_1,
        success: populateSource2,
        error: sourceError
    });
}

/**
 * Fires whether request is successful or not. Checks for errors, shows/hides
 * "source_2", <select>, etc.
 * 
 * 
 */
function sourceError() {
    source2Prep();
    $('#source_2').show();
    $('#source_2')[0].options.length = 0;
    var opt = new Option('An error has occurred...', '');
    addOption($('#source_2')[0], opt, 0);
}

/**
 * Populates "source_2" <select> with options.
 * 
 * 
 */
function populateSource2(xml) {
    // Hide source_2 <select> if nothing is selected in source_1 <select>.
    if ($('#source_1')[0].selectedIndex == 0) {
        $('#source_2').hide();
        return;
    }
    source2Prep();
    // Add "please select" first option.
    var opt = new Option('Please select...', '');
    addOption($('#source_2')[0], opt, 0);
    // Get <source> tags from XML retrieved from server.
    var xml_sources = xml.getElementsByTagName('source');
    // Add an <option> for each <source> in the XML.
    for (var i = 0; i < xml_sources.length; i++) {
        var source = xml_sources[i].childNodes[0].nodeValue;
        var opt = new Option(source, source);
        addOption($('#source_2')[0], opt, i + 1);
    }
    // Make sure "please select" option is selected.
    $('#source_2')[0].selectedIndex = 0;
}

/**
 * Shows or hides "source_2" <select>.
 * 
 * 
 */
function source2Prep() {
    if ($('#source_2').length) {
        // Show source_2 <select> in case it was previously hidden.
        $('#source_2').show();
        $('#source_2')[0].options.length = 0;
    } else {
        // Create source_2 <select>.
        var source_2 = document.createElement('SELECT');
        $(source_2).attr({ id:'source_2', name:'source_2' });
        $('#source_1').parent().append(source_2);
    }
}

/**
 * Adds an option to a <select>.
 * 
 * 
 */
function addOption(select, opt, index) {
    if ($.browser.msie) {
        select.add(opt, index);
    } else {
        select.appendChild(opt);
    }
}