Let there be a simple language like this:

expr ::= int | '(' op expr+ ')'
op ::= '+' | '*'

The task is to write a function int evaluate(String expression) that evaluates a given expression. You can assume that expression is valid for this given language.

Examples:

"3" = 3
"( + 1 2 )" = 3
"( + 3 4 5 )" = 12
"( + 7 ( * 8 12 ) ( * 2 ( + 9 4 ) 7 ) 3 )" = 288

I made some progress but wasn't able to finish it in time. I was trying to do it the same way as evaluating RPN and spent too much time exploring this incorrect idea.
The language explicitly puts spaces around each token and I think it's an important detail. It should probably be splitted by space and then parsed and evaluated recursively.