TextRange thenRange = then.getTextRange();
Document doc = editor.getDocument();
RangeMarker thenRangeMarker = doc.createRangeMarker(thenRange);
int lineStartOffset = doc.getLineStartOffset(doc.getLineNumber(thenRange.getEndOffset()));
doc.insertString(lineStartOffset, "}\n");
int lineEndOffset = doc.getLineEndOffset(doc.getLineNumber(thenRange.getStartOffset()));
doc.insertString(lineEndOffset, String.format("\nif %s {", rightExpr.getText()));
doc.deleteString(leftExpr.getTextRange().getEndOffset(), rightExpr.getTextRange().getEndOffset());