#![feature(core_intrinsics)]

use std::fmt;
use std::io::{self, Write};
use std::intrinsics::likely;

const WINDOW_SIZE: usize = 10;
const UPPER_BOUND: usize = 10;

struct FloatingWindow {
    data: [usize; WINDOW_SIZE],
    start_index: usize,
    current_size: usize,
    curr_sum: usize,
    counter: [usize; UPPER_BOUND]
}

impl FloatingWindow {
    pub fn new() -> Self {
        Self {
            start_index: 0,
            current_size: 0,
            data: [0; WINDOW_SIZE],
            curr_sum: 0,
            counter: [0; UPPER_BOUND],
        }
    }

    pub fn at(&self, idx: usize) -> usize {
        self.data[(self.start_index + idx) % WINDOW_SIZE]
    }

    pub fn push(&mut self, value: usize) {
        let old_value = self.at(self.current_size);
        self.curr_sum -= old_value;
        self.curr_sum += value;
        unsafe {
            if likely(self.counter[old_value] != 0) {
                self.counter[old_value] -= 1;
            }
        }
        self.counter[value] += 1;
        self.data[(self.start_index + self.current_size) % WINDOW_SIZE] = value;
        if self.current_size < WINDOW_SIZE {
            self.current_size += 1;
        } else {
            self.start_index += 1;
        }
    }

    pub fn sum(&self) -> usize {
        return self.curr_sum;
    }

    pub fn avg(&self) -> Option<usize> {
        if self.current_size != 0 {
            Some(self.curr_sum / (self.current_size))
        } else {
            None
        }
    }

    pub fn most_common(&self) -> usize {
        let mut num = 0;
        for (idx, &value) in self.counter.iter().enumerate() {
            if value > self.counter[num] {
                num = idx;
            }
        }
        num
    }
}

impl fmt::Debug for FloatingWindow {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(
            f,
            "FloatingWindow {{ {:?}, sum: {:?}, avg: {:?}, most_common: {:?} }}",
            self.into_iter().collect::<Vec<usize>>(),
            self.sum(),
            self.avg(),
            self.most_common()
        )
    }
}

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

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

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

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

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

    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 - 1))
        } else {
            None
        }
    }
}

fn main() {
    let stdin = io::stdin();
    let mut stdout = io::stdout();
    let mut user_input = String::new();
    let mut window = FloatingWindow::new();
    loop {
        print!("> ");
        stdout.flush().expect("I/O error");
        user_input.truncate(0);
        stdin.read_line(&mut user_input).expect("I/O error");

        if user_input == "" || user_input == "q\n" {
            break;
        }

        user_input = user_input.trim().to_string();

        if user_input == "" {
            continue;
        }

        if user_input == "p" {
            println!("{:?}", window);
        } else {
            match user_input.parse() {
                Ok(num) => {
                    if num >= UPPER_BOUND {
                        eprintln!("num must be less than {}", UPPER_BOUND);
                    } else {
                        window.push(num);
                    }
                }
                Err(err) => eprintln!("Error parsing number: {}", err),
            }
        }
    }
}