Mirror stamp tickets

Find out how many stamps it takes to turn a fairground ticket into a "mirror" ticket.

A ticket carries a positive whole number n. A number is a mirror number if it reads the same forwards and backwards in ordinary decimal digits (7, 4884 and 1001 are mirror numbers; 120 is not).

The booth attendant works like this: if the ticket's current number is a mirror number, she is done. Otherwise she stamps it, which replaces the number by *the number plus its reversal*. The reversal of a number is its digits written backwards, read as a normal number, so leading zeros of the reversal simply disappear (the reversal of 120 is 21). She stamps at most max_stamps times, and the number is checked again after every stamp, including the last one.

Input: n, a positive integer, and max_stamps, a non-negative integer.

Output: a list [stamps, value]: how many stamps were used and the final number on the ticket. If the number is still not a mirror number after max_stamps stamps, return [-1, value], where value is the number on the ticket after those max_stamps stamps.