use std::fmt;

#[derive(PartialEq)]
pub enum Player {
    Black,
    White,
}

impl fmt::Display for Player {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "{}",
            match self {
                Player::Black => "B",
                Player::White => "W",
            }
        )
    }
}

#[derive(PartialEq)]
pub enum Stone {
    Flat,
    Standing,
    Capstone,
}

impl fmt::Display for Stone {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "{}",
            match self {
                Stone::Flat => "",
                Stone::Standing => "S",
                Stone::Capstone => "C",
            }
        )
    }
}

pub struct Position {
    pub x: u8,
    pub y: u8,
}
impl fmt::Display for Position {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{:x}{}", 10 + self.x, self.y)
    }
}

pub enum Direction {
    Up,
    Down,
    Left,
    Right,
}

impl fmt::Display for Direction {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "{}",
            match self {
                Direction::Up => "+",
                Direction::Down => "-",
                Direction::Left => "<",
                Direction::Right => ">",
            }
        )
    }
}

pub enum Action {
    Place(Player, Position, Stone),
    Move(Player, Position, Direction, Vec<u8>),
}

impl fmt::Display for Action {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Action::Place(player, pos, stone) => write!(f, "{}{}{}", pos, player, stone),
            Action::Move(_, pos, direction, drops) => write!(
                f,
                "{}{}{}",
                pos,
                direction,
                drops.into_iter().map(|q| q.to_string()).collect::<String>()
            ),
        }
    }
}

type Stack = Vec<(Player, Stone)>;

pub struct Board {
    size: u16,
    black_flats: u8,
    white_flats: u8,
    black_capstones: u8,
    white_capstones: u8,
    board: Vec<Stack>,
}

// Probably it's best to split the move and place actions into their
// own methods, they should also take an extra argument which can be
// used to log error messages

// How to solve code duplication between is_legal_action and
// perform_action?

// TODO: Generate all legal actions for a given player

impl Board {
    fn lookup(&self, pos: &Position) -> Option<&Stack> {
        let y: u16 = pos.y as u16;
        let x: u16 = pos.x as u16;
        self.board.get((x + y * self.size) as usize)
    }

    fn is_legal_action(&self, mov: &Action) -> bool {
        match mov {
            Action::Place(player, pos, piece) => match self.lookup(pos) {
                Some(stack) => {
                    // Incomplete and incorrect, must take account of
                    // piece availabilty
                    if stack.len() == 0 {
                        true
                    } else {
                        false
                    }
                }
                None => false,
            },
            Action::Move(player, pos, direction, drops) => match self.lookup(pos) {
                Some(stack) => {
                    /* Rules for moving a stack:
                    0. There are stones
                    1. Top stone belongs to player
                    2. Zero or One stones dropped on starting square
                    3. Total number of stones moved does not exceed the carry capacity
                    4. Direction does not contain a capstone
                    5. Wall may only appear on last spot if it's capstone alone that covers
                    6. All stones are used up before then end of the board is met

                    We check 0,1,2, and 3 first
                     */
                    if (stack.len() == 0)
                        || (drops.len() == 0)
                        || (stack[0].0 != *player)
                        || (drops[0] > 1)
                        || (drops.iter().sum::<u8>() as u16 > self.size)
                    {
                        false
                    } else {
                        let steps: usize = drops.len() - 1;
                        let cap: bool = stack[0].1 == Stone::Capstone;
                        let (dy, dx): (i8, i8) = match direction {
                            Direction::Up => (1, 0),
                            Direction::Down => (-1, 0),
                            Direction::Left => (0, -1),
                            Direction::Right => (0, 1),
                        };

                        false
                    }
                }
                None => false,
            },
        }
    }
}