use std::ops::{Index, IndexMut};
use super::circular_index;

/// Game of Life universe building blocks (a plane is a circular Vec)
///
/// This is used internally in the implementation of the Universe to allow
/// more readable and safer traversing of the universe blocks
#[derive(Debug, Clone, PartialEq)]
pub(crate) struct Plane(pub Vec<bool>);

impl Index<isize> for Plane {
    type Output = bool;
    fn index(&self, idx: isize) -> &bool {
        let len = self.0.len() as isize;
        &self.0[circular_index(idx, len)]
    }
}

impl IndexMut<isize> for Plane {
    fn index_mut(&mut self, idx: isize) -> &mut Self::Output {
        let len = self.0.len() as isize;
        &mut self.0[circular_index(idx, len)]
    }
}

#[cfg(test)]
mod plane {
    use super::*;

    mod index {
        use super::*;

        #[test]
        fn get_element() {
            let p = Plane(vec![false, false, true, false, false]);
            assert_eq!(p[0], false);
            assert_eq!(p[1], false);
            assert_eq!(p[3], false);
            assert_eq!(p[4], false);

            assert_eq!(p[-3], true);
            assert_eq!(p[2], true);
            assert_eq!(p[7], true);
        }
    }

    #[cfg(test)]
    mod index_mut {
        use super::*;

        #[test]
        fn set_negative_index_element() {
            let mut p = Plane(vec![false, false, false, false, false]);
            p[-3] = true;
            assert_eq!(p, Plane(vec![false, false, true, false, false]));
        }

        #[test]
        fn set_element() {
            let mut p = Plane(vec![false, false, false, false, false]);
            p[2] = true;
            assert_eq!(p, Plane(vec![false, false, true, false, false]));
        }

        #[test]
        fn set_out_of_bound_element() {
            let mut p = Plane(vec![false, false, false, false, false]);
            p[7] = true;
            assert_eq!(p, Plane(vec![false, false, true, false, false]));
        }
    }
}