pub struct DoubleBuffer<T> {
    a1: Vec<T>,
    a2: Vec<T>,
    switch: bool,
}

impl<T> DoubleBuffer<T> {
    pub fn new(a1: Vec<T>, a2: Vec<T>) -> Self {
        Self { a1, a2, switch: false }
    }

    pub fn switch(&mut self) {
        self.switch = !self.switch;
    }

    pub fn first(&self) -> &Vec<T> {
        if self.switch { &self.a2 } else { &self.a1 }
    }

    pub fn first_mut(&mut self) -> &mut Vec<T> {
        if self.switch { &mut self.a2 } else { &mut self.a1 }
    }

    pub fn second(&self) -> &Vec<T> {
        if self.switch { &self.a1 } else { &self.a2 }
    }

    pub fn second_mut(&mut self) -> &mut Vec<T> {
        if self.switch { &mut self.a1 } else { &mut self.a2 }
    }
}