if (e.keyCode == 9) {
e.preventDefault();

// Multiline selection
if (selectionStart != selectionEnd && target.value.slice(selectionStart,selectionEnd).indexOf("\n") != -1) {
var pre = target.value.slice(0,selectionStart);
var sel = target.value.slice(selectionStart,selectionEnd);
var post = target.value.slice(selectionEnd,target.value.length);
if(sel.match(/\n(\t){1}/g))
var lines = sel.match(/\n(\t){1}/g).length + 1;
else
var lines = sel.split(/\n/).length;

if(!e.shiftKey) {
sel = sel.replace(/\n/g,"\n"+tab);
target.value = pre.concat(tab).concat(sel).concat(post);
target.selectionStart = selectionStart;
target.selectionEnd = selectionEnd + lines * tab.length;
} else {
if(sel.match(/^(\t){1}/m) || sel.match(/\n(\t){1}/g)) {
sel = sel.replace(/^(\t){1}/m,"");
sel = sel.replace(/\n(\t){1}/g,"\n");

target.value = pre.concat(sel).concat(post);
target.selectionStart = selectionStart;
target.selectionEnd = selectionEnd - lines * tab.length;
}
}
}
// No selection or sigle line selection
else {
if(!e.shiftKey) {
target.value = target.value.slice(0,selectionStart).concat(tab).concat(target.value.slice(selectionStart,target.value.length));
if (selectionStart == selectionEnd) {
target.selectionStart = target.selectionEnd = selectionStart + tab.length;
}
else {
target.selectionStart = selectionStart;
target.selectionEnd = selectionEnd + tab.length;
}
} else {
if (selectionStart != selectionEnd) {
var pre = target.value.slice(0,selectionStart);
var post = target.value.slice(selectionEnd,target.value.length);
var sel = target.value.slice(selectionStart,selectionEnd);

if (kc == 9 || (isSafari && kc == 25))
{
t.focus();

// hack for ie
if (!t.selectionStart)
{
var range = document.selection.createRange();
var stored_range = range.duplicate();
stored_range.moveToElementText(t);
stored_range.setEndPoint('EndToEnd', range);
t.selectionStart = stored_range.text.length - range.text.length;
t.selectionEnd = t.selectionStart + range.text.length;
t.setSelectionRange = function(start, end)
{
var range = this.createTextRange();
range.collapse(true);
range.moveStart("character", start);
range.moveEnd("character", end - start);
range.select();
}
}

var tablen = 4, tab = ' ', tab_regexp = /\n\s\s\s\s/g;
var ss = t.selectionStart, se = t.selectionEnd, ta_val = t.value, sel = ta_val.slice(ss, se); shft = (isSafari && kc == 25) || evt.shiftKey;
var was_tab = ta_val.slice(ss - tablen, ss) == tab, starts_with_tab = ta_val.slice(ss, ss + tablen) == tab, offset = shft ? 0-tablen : tablen, full_indented_line = false, num_lines = sel.split("\n").length;

if (ss != se && sel[sel.length-1] == '\n') { se--; sel = ta_val.slice(ss, se); num_lines--; }
if (num_lines == 1 && starts_with_tab) full_indented_line = true;

if (!shft || was_tab || num_lines > 1 || full_indented_line)
{
// multi-line selection
if (num_lines > 1)
{
// tab each line
if (shft && (was_tab || starts_with_tab) && sel.split(tab_regexp).length == num_lines)
{
if (!was_tab) sel = sel.substring(tablen);
t.value = ta_val.slice(0, ss - (was_tab ? tablen : 0)).concat(sel.replace(tab_regexp, "\n")).concat(ta_val.slice(se, ta_val.length));
ss += was_tab ? offset : 0; se += offset * num_lines;
}
else if (!shft)
{
t.value = ta_val.slice(0, ss).concat(tab).concat(sel.replace(/\n/g, "\n" + tab)).concat(ta_val.slice(se, ta_val.length));
se += offset * num_lines;
}
}

// single-line selection
else
{
if (shft)
t.value = ta_val.slice(0, ss - (full_indented_line ? 0 : tablen)).concat(ta_val.slice(ss + (full_indented_line ? tablen : 0), ta_val.length));
else
t.value = ta_val.slice(0, ss).concat(tab).concat(ta_val.slice(ss, ta_val.length));

if (ss == se)
ss = se = ss + offset;
else
se += offset;
}
}