#[derive(Clone)]
enum Color {
    Black,
    White,
}

impl Color {
    fn get_home_rank(&self) -> Rank {
        match self {
            Color::Black => Rank::_8,
            Color::White => Rank::_1,
        }
    }
    fn get_pawn_rank(&self) -> Rank {
        match self {
            Color::Black => Rank::_7,
            Color::White => Rank::_2,
        }
    }
    fn get_direction(&self) -> i8 {
        match self {
            Color::Black => -1,
            Color::White => 1,
        }
    }
}

#[derive(Clone)]
struct Position {
    rank: Rank,
    file: File,
}

impl Position {
    fn delta(&self, delta_rank_file: (i8, i8)) -> Result<Position, ()> {
        let (delta_rank, delta_file) = delta_rank_file;
        Ok(Position {
            rank: self.rank.delta(delta_rank)?,
            file: self.file.delta(delta_file)?,
        })
    }
}

#[derive(PartialEq, Clone, Copy)]
enum Rank {
    _1,
    _2,
    _3,
    _4,
    _5,
    _6,
    _7,
    _8,
}

#[derive(PartialEq, Clone, Copy)]
enum File {
    A,
    B,
    C,
    D,
    E,
    F,
    G,
    H,
}

trait GridAxis
where
    Self: Sized,
    Self: Clone,
{
    const ALL_VALUES: [Self; 8];
    fn new(index: u8) -> Result<Self, ()> {
        return Ok(
            Self::ALL_VALUES[Self::validate_index(index)? as usize].clone()
        );
    }
    fn validate_index(index: u8) -> Result<u8, ()> {
        if index as usize >= Self::ALL_VALUES.len() {
            Err(())
        } else {
            Ok(index)
        }
    }
    fn get_index(&self) -> u8;
    fn delta(&self, delta: i8) -> Result<Self, ()> {
        let highest = Self::ALL_VALUES.len() as i8 - 1;
        if delta > highest
            || delta < -highest
            || (delta < 0 && self.get_index() < delta.abs() as u8)
            || (delta > 0 && self.get_index() + delta as u8 > highest as u8)
        {
            Err(())
        } else {
            Ok(Self::new(((self.get_index() as i8) + delta) as u8)?)
        }
    }
}

impl GridAxis for Rank {
    const ALL_VALUES: [Rank; 8] = [
        Rank::_1,
        Rank::_2,
        Rank::_3,
        Rank::_4,
        Rank::_5,
        Rank::_6,
        Rank::_7,
        Rank::_8,
    ];
    fn get_index(&self) -> u8 {
        *self as u8
    }
}

impl GridAxis for File {
    const ALL_VALUES: [File; 8] = [
        File::A,
        File::B,
        File::C,
        File::D,
        File::E,
        File::F,
        File::G,
        File::H,
    ];
    fn get_index(&self) -> u8 {
        *self as u8
    }
}

#[derive(Clone)]
enum PieceType {
    Pawn,
}

impl PieceType {
    fn initial_setup(&self) -> Vec<Piece> {
        match &self {
            PieceType::Pawn => [Color::Black, Color::White]
                .iter()
                .flat_map(|color| {
                    File::ALL_VALUES.iter().map(|&file| Piece {
                        piece_type: self.clone(),
                        position: Position {
                            rank: color.get_pawn_rank(),
                            file,
                        },
                        color: color.clone(),
                    })
                })
                .collect(),
        }
    }
}

struct Piece {
    position: Position,
    color: Color,
    piece_type: PieceType,
}

trait Movement {
    fn get_moves(&self) -> Vec<Position>;
    fn get_captures(&self) -> Vec<Position>;
}

impl Piece {
    fn get_moves(&self) -> Vec<Position> {
        let deltas = match self.piece_type {
            PieceType::Pawn => self._pawn_get_move_deltas(),
        };
        self.deltas_to_valid_positions(&deltas)
    }
    fn get_captures(&self) -> Vec<Position> {
        let deltas = match self.piece_type {
            PieceType::Pawn => self._pawn_get_capture_deltas(),
        };
        self.deltas_to_valid_positions(&deltas)
    }
    fn deltas_to_valid_positions(
        &self,
        deltas: &Vec<(i8, i8)>,
    ) -> Vec<Position> {
        deltas
            .iter()
            .filter_map(|&delta_rank_file| {
                self.position.delta(delta_rank_file).ok()
            })
            .collect()
    }
    fn _pawn_get_move_deltas(&self) -> Vec<(i8, i8)> {
        let direction = self.color.get_direction();
        if self.position.rank == self.color.get_pawn_rank() {
            vec![(1 * direction, 0), (2 * direction, 0)]
        } else {
            vec![(1 * direction, 0)]
        }
    }
    fn _pawn_get_capture_deltas(&self) -> Vec<(i8, i8)> {
        let direction = self.color.get_direction();
        vec![(1 * direction, 1), (1 * direction, -1)]
    }
}

struct Board {
    state: [[Option<Piece>; File::ALL_VALUES.len()]; Rank::ALL_VALUES.len()],
}

impl Board {
    fn set_at(&mut self, position: &Position, piece: Piece) {
        self.state[position.rank.get_index() as usize]
            [position.file.get_index() as usize] = Some(piece);
    }
    fn new() -> Board {
        let mut board = Board {
            state: Default::default(),
        };
        for piece_type in &[PieceType::Pawn] {
            for piece in piece_type.initial_setup() {
                board.set_at(&piece.position.clone(), piece);
            }
        }
        board
    }
}

fn main() {}