#[derive(Clone, Copy, PartialEq)]
pub enum Cell {
    Empty,
    X,
    O,
}

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

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

impl Board {
    pub fn new() -> Board {
        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 apply(&mut self, m: Move) -> Result<(), &str> {
        if !self.is_valid_move(&m) {
            return Err("invalid move");
        }

        let i = m.x * 1 + m.y * 3;
        self.cells[i] = m.piece;

        match self.next {
            Cell::X => self.next = Cell::O,
            Cell::O => self.next = Cell::X,
            _ => {}
        }

        Ok(())
    }

    pub fn is_valid_move(&self, m: &Move) -> bool {
        if m.x > 2 || m.y > 2 {
            return false;
        }

        let i = m.x * 1 + m.y * 3;

        m.piece == self.next && self.cells[i] == Cell::Empty
    }

    pub fn valid_moves_available(&self) -> bool {
        // check for draw condition
        for i in 0..self.cells.len() {
            if self.cells[i] == Cell::Empty {
                return true;
            }
        }

        return false;
    }

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

        // diagonals
        if (self.cells[0] != Cell::Empty)
            && (self.cells[0] == self.cells[4] && self.cells[0] == self.cells[8])
        {
            return Some(self.cells[0]);
        }

        if (self.cells[2] != Cell::Empty)
            && (self.cells[2] == self.cells[4] && self.cells[2] == self.cells[6])
        {
            return Some(self.cells[2]);
        }

        // no winner
        return None;
    }

    pub fn cells(&self) -> Vec<Cell> {
        self.cells.clone()
    }

    pub fn next_move(&self) -> Cell {
        self.next
    }
}