Ext.ns('FileDownloader');

/**
 * Given a URL this function will create a hidden form and post its (empty) contents
 * to the specified URL. If the response contains an appropriate header the user will
 * be prompted for a file download.
 *
 * @param url The URL to download to
 * @param parameters [Optional] a javascript object containing parameter key value pairs to be posted. The values may consist of Javascript primitives or Arrays
 */
FileDownloader.downloadFile = function(url, parameters) {
    //build our list of input children first
    var inputs = [];
    if (parameters) {
        for (var key in parameters) {
            if (!key) {
                continue;
            }

            //We need to treat arrays and objects
            var value = parameters[key];
            if (!Ext.isArray(value)) {
                value = [value];
            }

            //Build a number of Ext.DomHelper config objects representing the inputs
            for (var i = 0; i < value.length; i++) {
                inputs.push({
                    tag : 'input',
                    id : String.format('portal-input-{0}-{1}', key, i),
                    type : 'hidden',
                    name : key,
                    value : value[i]
                });
            }
        }
    }

    var body = Ext.getBody();
    var frame = body.createChild({
        tag : 'iframe',
        id : 'portal-iframe',
        name : 'iframe'
    });
    var form = body.createChild({
        tag : 'form',
        id : 'portal-form',
        target : 'portal-iframe',
        method : 'POST',
        children : inputs
    });

    form.dom.action = url;
    form.dom.submit();
};