use std::collections::VecDeque;


pub struct EventQueue<E> {
    queue: VecDeque<E>,
}

impl<E> EventQueue<E> {
    pub const fn new() -> Self {
        Self { queue: VecDeque::new() }
    }

    pub fn read(&mut self) -> Option<E> {
        self.queue.pop_front()
    }

    pub fn write(&mut self, event: E) {
        self.queue.push_back(event);
    }

    pub fn drain(&mut self) -> Vec<E> {
        self.queue.drain(..).collect()
    }

    pub fn as_reader(&mut self) -> EventReader<E> {
        EventReader { queue: &mut self.queue }
    }

    pub fn as_writer(&mut self) -> EventWriter<E> {
        EventWriter { queue: &mut self.queue }
    }
}

impl<E> Iterator for EventQueue<E> {
    type Item = E;

    fn next(&mut self) -> Option<E> {
        self.read()
    }
}


pub struct EventReader<'q, E> {
    queue: &'q mut VecDeque<E>,
}

impl<E> EventReader<'_, E> {
    pub fn read(&mut self) -> Option<E> {
        self.queue.pop_front()
    }
}


pub struct EventWriter<'q, E> {
    queue: &'q mut VecDeque<E>,
}

impl<E> EventWriter<'_, E> {
    pub fn write(&mut self, event: E) {
        self.queue.push_front(event)
    }
}


impl<E> Iterator for EventReader<'_, E> {
    type Item = E;

    fn next(&mut self) -> Option<E> {
        self.read()
    }
}