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

use std::slice::SliceIndex;

pub struct Vec2D<T> {

    data: Vec<T>,

    width: usize,

    height: usize,

}

impl<T> Index<usize> for Vec2D<T> {

    type Output = [T];

    #[inline]

    fn index(&self, row: usize) -> &[T] {

        debug_assert!(row < self.height);

        let pos = row * self.width;

        &self.data[pos..pos + self.width]

    }

}

impl<T> IndexMut<usize> for Vec2D<T> {

    #[inline]

    fn index_mut(&mut self, row: usize) -> &mut [T] {

        debug_assert!(row < self.height);

        let pos = row * self.width;

        &mut self.data[pos..pos + self.width]

    }

}

impl<T: Copy> Vec2D<T> {

    pub fn new(width: usize, height: usize, value: T) -> Self {

        Self {

            data: vec![value; width * height],

            width,

            height,

        }

    }

    #[inline]

    pub fn width(&self) -> usize {

        self.width

    }

    #[inline]

    pub fn height(&self) -> usize {

        self.height

    }

    #[inline]

    pub fn get_mut(&mut self, row: usize, column: usize) -> Option<&mut <usize as SliceIndex<[T]>>::Output> {

        self.data.get_mut(row * self.width + column)

    }

}

#[cfg(test)]

mod tests {

    use super::*;

    #[test]

    fn basics() {

        let mut v: Vec2D<u8> = Vec2D::new(2, 3, 0xff);

        assert_eq!(v.width, 2);

        assert_eq!(v.height, 3);

        assert_eq!(v[0][0], 0xff);

        assert_eq!(v[2][1], 0xff);

        v[2][1] = 0;

        assert_eq!(v[2][0], 0xff);

        assert_eq!(v[2][1], 0);

        v.get_mut(2, 1).map(|v| *v = 1);

        assert_eq!(v[2][1], 1);

        assert_eq!(v.get_mut(2, 2), None);

    }

}