Smart Brackets

script

// If a selection is present, wrap the text.
//
// If no selection, scan text for last open or close and
// close it if last one was an open, or
// insert open if not.

const open = "[";
const close = "]";

const range = editor.getSelectedRange();
const priorText = editor.getTextInRange(0, range[0]);

if (range[1] > 0) { 
 //text selected, wrap it!
 editor.setSelectedText(open + editor.getSelectedText() + close);
 editor.setSelectedRange(range[0] + range[1] + open.length + close.length, 0);
}
else {
 // no selection, find last 
 const lastOpen = priorText.lastIndexOf(open);
 const lastClose = priorText.lastIndexOf(close);
 
 if (lastOpen == -1 || lastClose > lastOpen) { // no close, use open
   editor.setSelectedText(open);
   editor.setSelectedRange(range[0]+open.length, 0);
 }
 else { // close last open
   editor.setSelectedText(close);
   editor.setSelectedRange(range[0]+close.length, 0);
 }
}