const WINDOW_SIZE: usize = 10;

struct FloatingWindow<'a> {
    data: [i64; WINDOW_SIZE],
    start_index: usize,
    current_size: usize,
}

impl<'a> FloatingWindow<'a> {
    pub fn at(&self, idx: usize) -> i64 {
        self.data[(self.start_index + idx) % WINDOW_SIZE]
    }
}


struct FloatingWindowIterator<'a> {
    window: &'a FloatingWindow<'a>,
    curr_index: usize
}

impl<'a> IntoIterator for FloatingWindow<'a> {
    type Item = i64;
    type IntoIter = FloatingWindowIterator<'a>;

    fn into_iter(&self) -> Self::IntoIter {
        FloatingWindowIterator::new(&self)
    }
}

impl<'a> FloatingWindowIterator<'a> {
    pub fn new(window: &'a FloatingWindow) -> FloatingWindowIterator<'a> {
        FloatingWindowIterator {
            window,
            curr_index: 0
        }
    }
}

impl<'a> Iterator for FloatingWindowIterator<'a> {
    type Item = i64;

    fn next(&mut self) -> Option<Self::Item> {
        if self.curr_index < self.window.current_size {
            self.curr_index += 1;
            Some(self.window.at(self.curr_index))
        } else {
            None
        }
    }
}

fn main() {
    println!("Hello!");
}