var xmlHttp = false;
 if (!xmlHttp && typeof XMLHttpRequest != 'undefined') {
				xmlHttp = new XMLHttpRequest();
 } 

// ------------------------------------- switch button func -------------------------------------------
function switch_but(el_id) {
	if (document.getElementById(el_id).style.display=='') {
		document.getElementById(el_id).style.display='none';
		document.getElementById(el_id+'1').style.display='';
	}
	else {
		document.getElementById(el_id).style.display='';
		document.getElementById(el_id+'1').style.display='none';
	}
}
//--------------------------------------  space trim function  ----------------------------------------
function trim (str) {	
	str=str.replace(/^\s+/, '').replace(/\s+$/, '');
	str=str.replace('<','');
	str=str.replace('>','');
	return str
}

//--------------------------------------  input control function ---------------------------------
function start_send() {
	switch_but('send_but');
	var user_name = document.getElementById('user_name').value;
	var user_tel = document.getElementById('user_tel').value;
	var user_mail = document.getElementById('user_mail').value;
	var user_quest = document.getElementById('user_quest').value;
	var user_theme = document.getElementById('user_theme').value;
	
	user_name = trim(user_name);
	user_tel = trim(user_tel);
	user_mail = trim(user_mail);
	user_quest = trim(user_quest);
	user_theme = trim(user_theme);
	
	
	err_str = '';
	if (user_name == '') {
		err_str += ' - Name \n';
	}
	if (user_tel == '') {
		err_str += ' - Telefon \n';
	}
	if (user_mail == '') {
		err_str += ' - E-Mail \n';
	}
	if (user_quest == '') {
		err_str += ' - Ihre Frage oder Bestellung \n';
	}
	if (err_str == '') {
		send_mail(user_name, user_tel, user_mail, user_quest, user_theme);
	}
	else {
		err_str = 'Fehler. Möglicherweise ist das folgende Feld nicht ausgefüllt: \n'+err_str;
		alert(err_str);
		switch_but('send_but');
	}
}  

// -------------------------------------  send mail function   ------------------------------------------
function send_mail (usr_name,usr_tel,usr_mail,usr_quest,usr_theme) {
	xmlHttp.open('POST', '../scripts/send_de.php', true);
	xmlHttp.onreadystatechange = getSendResult;
	xmlHttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
	xmlHttp.send('user_name='+usr_name+'&user_tel='+usr_tel+'&user_mail='+usr_mail+'&user_quest='+usr_quest+'&user_theme='+usr_theme);
}

//--------------------------------------  UPDATE PAGE FUNCTION --------------------------------
function getSendResult() {
	if (xmlHttp.readyState == 4 && xmlHttp.status==200) {
		var response = xmlHttp.responseText;
		if (response == 'allright') {
			document.getElementById('user_name').value='';
			document.getElementById('user_tel').value='';
			document.getElementById('user_mail').value='';
			document.getElementById('user_quest').value='';
			document.getElementById('user_theme').value='';
			alert('Ihre Nachricht wurde erfolgreich verschickt.');
		}
		else {
			alert('Entschuldigung, leider kann Ihre Nachricht im Moment nicht verschickt  werden.')
		}
		switch_but('send_but');
	}
}