#[derive(Clone, Copy, PartialEq)]
pub struct Cell(u8);
pub const CELL_EMPTY: Cell = Cell(0);
pub const CELL_X: Cell = Cell(1);
pub const CELL_O: Cell = Cell(2);

impl std::fmt::Display for Cell {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        let mut s: &str = " ";
        if *self == CELL_X {
            s = "X";
        } else if *self == CELL_O {
            s = "O";
        }

        write!(f, "{}", s)
    }
}

pub struct Move {
    pub x: usize,
    pub y: usize,
    pub c: Cell,
}

pub struct Board {
    cells: Vec<Cell>,
    next: Cell,
}

impl Board {
    pub fn new() -> Board {
        return Board {
            cells: vec![CELL_EMPTY; 9],
            next: CELL_X,
        };
    }

    pub fn reset(&mut self) {
        self.cells = vec![CELL_EMPTY; 9];
        self.next = CELL_X;
    }

    pub fn put(&mut self, m: Move) -> bool {
        let i = m.x * 1 + m.y * 3;
        if self.cells[i] != CELL_EMPTY {
            return false;
        }

        self.cells[i] = m.c;

        return true;
    }

    pub fn has_winner(&self) -> Cell {
        // rows and cols
        for i in 0..3 {
            if self.cells[i] == self.cells[i + 3] && self.cells[i] == self.cells[i + 6] {
                return self.cells[i];
            } else if self.cells[i * 3] == self.cells[i * 3 + 1]
                && self.cells[i * 3] == self.cells[i * 3 + 2]
            {
                return self.cells[i * 3];
            }
        }

        // diagonals
        if self.cells[0] == self.cells[4] && self.cells[0] == self.cells[8] {
            return self.cells[0];
        }

        if self.cells[2] == self.cells[4] && self.cells[2] == self.cells[6] {
            return self.cells[2];
        }

        // no winner
        return CELL_EMPTY;
    }
}

impl std::fmt::Display for Board {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        let mut s = String::new();

        s.push_str("┌─┬─┬─┐\n");
        for i in 0..3 {
            s.push_str(&format!(
                "│{}│{}│{}│\n",
                self.cells[i * 3],
                self.cells[i * 3 + 1],
                self.cells[i * 3 + 2]
            ));
            if i < 2 {
                s.push_str("├─┼─┼─┤\n");
            }
        }
        s.push_str("└─┴─┴─┘\n");

        let w = self.has_winner();
        if w != CELL_EMPTY {
            s.push_str(&format!("The winner is {w}"));
        } else {
            s.push_str(&format!("Next: {}", self.next));
        }
        write!(f, "{s}")
    }
}