use crate::{Coord, Rect};

/// A `Board` represents a two-dimensional grid with a fixed width and
/// height. Indexing always starts from (0, 0)
#[derive(PartialEq, Eq, Debug)]
pub struct Board<T> {
    width: usize,
    height: usize,
    storage: Vec<T>,
}

impl<T: Clone> Board<T> {
    pub fn new_with_default(width: usize, height: usize, default: T) -> Board<T> {
        let mut storage = Vec::with_capacity(width * height);
        for _ in 0..width * height {
            storage.push(default.clone())
        }
        Board {
            width,
            height,
            storage,
        }
    }
}

impl<T> Board<T> {
    pub fn new_from(
        width: usize,
        height: usize,
        mut func: impl FnMut(usize, usize) -> T,
    ) -> Board<T> {
        let mut storage = Vec::with_capacity(width * height);
        for y in 0..height {
            for x in 0..width {
                storage.push(func(x, y))
            }
        }
        Board {
            width,
            height,
            storage,
        }
    }

    /// Returns a reference to an element at the given location, or
    /// `None` if the location is out of bounds.
    pub fn get(&self, x: usize, y: usize) -> Option<&T> {
        if !self.contains([x, y]) {
            return None;
        }
        let idx = x + self.width * y;
        self.storage.get(idx)
    }

    /// Returns a mutable reference to an element at the given
    /// location, or `None` if the location is out of bounds.
    pub fn get_mut(&mut self, x: usize, y: usize) -> Option<&mut T> {
        if !self.contains([x, y]) {
            return None;
        }
        let idx = x + self.width * y;
        self.storage.get_mut(idx)
    }

    /// Returns the width of the board
    pub fn width(&self) -> usize {
        self.width
    }

    /// Returns the height of the board
    pub fn height(&self) -> usize {
        self.height
    }

    /// Returns `true` if the given position is in-bounds in the
    /// board; otherwise returns false
    pub fn contains(&self, pos: impl Into<Coord>) -> bool {
        let pos = pos.into();
        pos.x < self.width && pos.y < self.height
    }

    pub fn contains_rect(&self, rect: Rect) -> bool {
        let max_x = rect.width() + rect.x() - 1;
        let max_y = rect.height() + rect.y() - 1;
        self.contains([max_x, max_y])
    }

    /// Returns an iterator over the board in row-major order; this
    /// iterator returns not only the values contained in the board,
    /// but also their indices.
    pub fn iter(&self) -> BoardIter<T> {
        BoardIter {
            n: 0,
            width: self.width,
            iter: self.storage.iter(),
        }
    }

    /// Returns an iterator over the board in row-major order; this
    /// iterator returns not only the values contained in the board,
    /// but also their indices.
    pub fn iter_mut(&mut self) -> BoardIterMut<T> {
        BoardIterMut {
            n: 0,
            width: self.width,
            iter: self.storage.iter_mut(),
        }
    }

    pub fn window_iter(&self, window: Rect) -> Option<BoardWindowIter<T>> {
        if !self.contains_rect(window) {
            return None;
        }
        Some(BoardWindowIter {
            n: 0,
            width: self.width,
            window,
            iter: self.storage.iter(),
        })
    }

    pub fn window_iter_mut(&mut self, window: Rect) -> Option<BoardWindowIterMut<T>> {
        if !self.contains_rect(window) {
            return None;
        }
        Some(BoardWindowIterMut {
            n: 0,
            width: self.width,
            window,
            iter: self.storage.iter_mut(),
        })
    }
}

impl<T> std::ops::Index<Coord> for Board<T> {
    type Output = T;

    fn index(&self, pos: Coord) -> &Self::Output {
        self.get(pos.x, pos.y)
            .unwrap_or_else(|| panic!("Coordinate {:?} out of range", pos))
    }
}

impl<T> std::ops::Index<(usize, usize)> for Board<T> {
    type Output = T;

    fn index(&self, (x, y): (usize, usize)) -> &Self::Output {
        self.get(x, y)
            .unwrap_or_else(|| panic!("Coordinate {:?} out of range", (x, y)))
    }
}

impl<T> std::ops::Index<[usize; 2]> for Board<T> {
    type Output = T;

    fn index(&self, [x, y]: [usize; 2]) -> &Self::Output {
        self.get(x, y)
            .unwrap_or_else(|| panic!("Coordinate {:?} out of range", (x, y)))
    }
}

impl<T> std::ops::IndexMut<Coord> for Board<T> {
    fn index_mut(&mut self, pos: Coord) -> &mut Self::Output {
        self.get_mut(pos.x, pos.y)
            .unwrap_or_else(|| panic!("Coordinate {:?} out of range", pos))
    }
}

impl<T> std::ops::IndexMut<(usize, usize)> for Board<T> {
    fn index_mut(&mut self, (x, y): (usize, usize)) -> &mut Self::Output {
        self.get_mut(x, y)
            .unwrap_or_else(|| panic!("Coordinate {:?} out of range", (x, y)))
    }
}

impl<T> std::ops::IndexMut<[usize; 2]> for Board<T> {
    fn index_mut(&mut self, [x, y]: [usize; 2]) -> &mut Self::Output {
        self.get_mut(x, y)
            .unwrap_or_else(|| panic!("Coordinate {:?} out of range", (x, y)))
    }
}

/// An iterator over the elements of a `Board`. This returns values in
/// row-major order but each element is also accompanied by its
/// indices.
pub struct BoardIter<'a, T> {
    n: usize,
    width: usize,
    iter: std::slice::Iter<'a, T>,
}

impl<'a, T> Iterator for BoardIter<'a, T> {
    type Item = (usize, usize, &'a T);

    fn next(&mut self) -> Option<Self::Item> {
        if let Some(v) = self.iter.next() {
            let x = self.n % self.width;
            let y = self.n / self.width;
            self.n += 1;
            Some((x, y, v))
        } else {
            None
        }
    }
}

/// An iterator over the elements of a `Board`. This returns values in
/// row-major order but each element is also accompanied by its
/// indices.
pub struct BoardIterMut<'a, T> {
    n: usize,
    width: usize,
    iter: std::slice::IterMut<'a, T>,
}

impl<'a, T> Iterator for BoardIterMut<'a, T> {
    type Item = (usize, usize, &'a mut T);

    fn next(&mut self) -> Option<Self::Item> {
        if let Some(v) = self.iter.next() {
            let x = self.n % self.width;
            let y = self.n / self.width;
            self.n += 1;
            Some((x, y, v))
        } else {
            None
        }
    }
}

pub struct BoardWindowIter<'a, T> {
    n: usize,
    width: usize,
    window: Rect,
    iter: std::slice::Iter<'a, T>,
}

impl<'a, T> Iterator for BoardWindowIter<'a, T> {
    type Item = (usize, usize, &'a T);

    fn next(&mut self) -> Option<Self::Item> {
        while let Some(v) = self.iter.next() {
            let x = self.n % self.width;
            let y = self.n / self.width;
            self.n += 1;
            if self.window.contains([x, y]) {
                return Some((x, y, v));
            }
        }
        None
    }
}

pub struct BoardWindowIterMut<'a, T> {
    n: usize,
    width: usize,
    window: Rect,
    iter: std::slice::IterMut<'a, T>,
}

impl<'a, T> Iterator for BoardWindowIterMut<'a, T> {
    type Item = (usize, usize, &'a mut T);

    fn next(&mut self) -> Option<Self::Item> {
        while let Some(v) = self.iter.next() {
            let x = self.n % self.width;
            let y = self.n / self.width;
            self.n += 1;
            if self.window.contains([x, y]) {
                return Some((x, y, v));
            }
        }
        None
    }
}

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

    macro_rules! board_from_vec {
        ($w:expr, $h:expr; [$($vec:tt)*]) => {
            {
                let w = $w;
                let h = $h;
                let v = vec![$($vec)*];
                assert!(v.len() == w * h);
                Board::new_from(w, h, |x, y| {
                    v[x + y * w]
                })
            }
        }
    }

    #[test]
    fn board_indexing() {
        let b = board_from_vec![2,2; [1,2,3,4]];
        // in-bounds tests
        assert_eq!(b.get(0, 0), Some(&1));
        assert_eq!(b.get(1, 0), Some(&2));
        assert_eq!(b.get(0, 1), Some(&3));
        assert_eq!(b.get(1, 1), Some(&4));
        // out-of-bounds tests
        assert_eq!(b.get(2, 0), None);
        assert_eq!(b.get(0, 2), None);
        assert_eq!(b.get(2, 2), None);
    }

    #[test]
    fn board_mut_indexing() {
        let mut b = board_from_vec![2,2; [1,2,3,4]];
        // in-bounds tests
        *b.get_mut(0, 0).unwrap() = 5;
        *b.get_mut(1, 0).unwrap() = 6;
        *b.get_mut(0, 1).unwrap() = 7;
        *b.get_mut(1, 1).unwrap() = 8;

        assert_eq!(b, board_from_vec![2,2; [5,6,7,8]]);
    }

    #[test]
    fn board_iter() {
        let b = board_from_vec![2,2; [1,2,3,4]];
        let mut iter = b.iter();
        // in-bounds tests
        assert_eq!(iter.next(), Some((0, 0, &1)));
        assert_eq!(iter.next(), Some((1, 0, &2)));
        assert_eq!(iter.next(), Some((0, 1, &3)));
        assert_eq!(iter.next(), Some((1, 1, &4)));
        assert_eq!(iter.next(), None);
    }

    #[test]
    fn board_iter_mut() {
        let mut b = board_from_vec![2,2; [1,2,3,4]];
        // in-bounds tests
        for (x, y, r) in b.iter_mut() {
            *r = x * 2 + y * 2;
        }
        assert_eq!(b, board_from_vec![2,2; [0,2,2,4]]);
    }

    #[test]
    fn window_iter() {
        let b = board_from_vec![
            4,4;
            [1,2,3,4,
             5,6,7,8,
             8,7,6,5,
             4,3,2,1,
            ]
        ];

        let mut iter = b
            .window_iter(Rect {
                origin: [1, 1].into(),
                size: [2, 2].into(),
            })
            .expect("Did not find expected BoardWindowIter");
        // in-bounds tests
        assert_eq!(iter.next(), Some((1, 1, &6)));
        assert_eq!(iter.next(), Some((2, 1, &7)));
        assert_eq!(iter.next(), Some((1, 2, &7)));
        assert_eq!(iter.next(), Some((2, 2, &6)));
        assert_eq!(iter.next(), None);
    }

    #[test]
    fn window_iter_mut() {
        let mut b: Board<isize> = board_from_vec![
        4,4;
        [1,2,3,4,
         5,6,7,8,
         8,7,6,5,
         4,3,2,1,
        ]];

        let iter = b
            .window_iter_mut(Rect {
                origin: [1, 1].into(),
                size: [2, 2].into(),
            })
            .expect("Did not find expected BoardWindowIterMut");
        for (x, y, v) in iter {
            *v = -(2 * x as isize + 2 * y as isize);
        }

        assert_eq!(
            b,
            board_from_vec![
                4,4;
                [ 1, 2, 3, 4,
                  5,-4,-6, 8,
                  8,-6,-8, 5,
                  4, 3, 2, 1,
                ]
            ]
        );
    }
}