use ijvm::Result;

#[derive(Debug)]
pub struct Stack {
    pub data: Vec<i32>
}

impl Stack {
    pub fn new() -> Stack {
        Stack {
            data: Vec::new()
        }
    }

//    pub fn len(&self) -> usize {
//        return self.data.len();
//    }

    pub fn top(&self) -> Result<i32> {
        Ok(match  self.data.last() {
            Some(a) => *a,
            None => return Err("Stack empty"),
        })
    }

    pub fn pop(&mut self) -> Result<i32> {
        Ok(match self.data.pop() {
            Some(a) => a,
            None => return Err("Stack empty"),
        })
    }

    pub fn push(&mut self, val: i32) {
        self.data.push(val);
    }

    pub fn len(&self) -> usize {
        self.data.len()
    }
}