use std::collections::HashSet;

const WHITE_PAWN: char = '♙';
const WHITE_KNIGHT: char = '♘';
const WHITE_BISHOP: char = '♗';
const WHITE_ROOK: char = '♖';
const WHITE_QUEEN: char = '♕';
const WHITE_KING: char = '♔';
const BLACK_PAWN: char = '♟';
const BLACK_KNIGHT: char = '♞';
const BLACK_BISHOP: char = '♝';
const BLACK_ROOK: char = '♜';
const BLACK_QUEEN: char = '♛';
const BLACK_KING: char = '♚';

#[derive(Debug, Copy, Clone, PartialEq, PartialOrd)]
#[rustfmt::skip]
pub enum BoardPosition {
    A1, A2, A3, A4, A5, A6, A7, A8,
    B1, B2, B3, B4, B5, B6, B7, B8,
    C1, C2, C3, C4, C5, C6, C7, C8,
    D1, D2, D3, D4, D5, D6, D7, D8,
    E1, E2, E3, E4, E5, E6, E7, E8,
    F1, F2, F3, F4, F5, F6, F7, F8,
    G1, G2, G3, G4, G5, G6, G7, G8,
    H1, H2, H3, H4, H5, H6, H7, H8,
}

impl From<BoardPosition> for usize {
    #[rustfmt::skip]
    fn from(square: BoardPosition) -> Self {
        use BoardPosition::*;

        match square {
            A1 => 0, A2 => 1, A3 => 2, A4 => 3,
            A5 => 4, A6 => 5, A7 => 6, A8 => 7,

            B1 => 8, B2 => 9, B3 => 10, B4 => 11,
            B5 => 12, B6 => 13, B7 => 14, B8 => 15,

            C1 => 16, C2 => 17, C3 => 18, C4 => 19,
            C5 => 20, C6 => 21, C7 => 22, C8 => 23,

            D1 => 24, D2 => 25, D3 => 26, D4 => 27,
            D5 => 28, D6 => 29, D7 => 30, D8 => 31,

            E1 => 32, E2 => 33, E3 => 34, E4 => 35,
            E5 => 36, E6 => 37, E7 => 38, E8 => 39,

            F1 => 40, F2 => 41, F3 => 42, F4 => 43,
            F5 => 44, F6 => 45, F7 => 46, F8 => 47,

            G1 => 48, G2 => 49, G3 => 50, G4 => 51,
            G5 => 52, G6 => 53, G7 => 54, G8 => 55,

            H1 => 56, H2 => 57, H3 => 58, H4 => 59,
            H5 => 60, H6 => 61, H7 => 62, H8 => 63,
        }
    }
}

#[derive(Debug, Copy, Clone, PartialEq, Hash, Eq)]
pub enum MoveAmount {
    One,
    Two,
    Many,
}

#[derive(Debug, Clone, PartialEq, Hash, Eq)]
pub enum MoveType {
    Vertical(MoveAmount),
    Horizontal(MoveAmount),
    Diagonal(MoveAmount),
    Knight,
    KingSideCastle,
    QueenSideCastle,
    EnPassant,
    Promoted(PieceType),
}

#[derive(Debug, Copy, Clone, PartialEq)]
pub enum PieceColor {
    Black,
    White,
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
/// Which set of squares can this bishop use?
pub enum BishopType {
    /// Only dark/black squares
    Dark,

    /// Only light/red squares
    Light,
}

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum PieceType {
    Pawn(Option<Box<PieceType>>),
    Rook,
    Knight,
    King,
    Queen,
    Bishop(BishopType),
}

#[derive(Debug, PartialEq)]
pub struct Piece {
    kind: PieceType,
    color: PieceColor,
    symbol: char,
}

impl Piece {
    pub fn new(color: PieceColor, kind: PieceType) -> Self {
        Self {
            kind: kind.clone(),
            color,
            symbol: Self::get_symbol(color, kind),
        }
    }

    pub fn get_symbol(color: PieceColor, kind: PieceType) -> char {
        use PieceColor::*;
        use PieceType::*;

        match (color, kind) {
            // Treat promoted pawns as their promoted type
            (c, Pawn(Some(k))) => Self::get_symbol(c, *k),

            (White, Pawn(None)) => WHITE_PAWN,
            (White, Knight) => WHITE_KNIGHT,
            (White, Bishop(_)) => WHITE_BISHOP,
            (White, Rook) => WHITE_ROOK,
            (White, Queen) => WHITE_QUEEN,
            (White, King) => WHITE_KING,
            (Black, Pawn(None)) => BLACK_PAWN,
            (Black, Knight) => BLACK_KNIGHT,
            (Black, Bishop(_)) => BLACK_BISHOP,
            (Black, Rook) => BLACK_ROOK,
            (Black, Queen) => BLACK_QUEEN,
            (Black, King) => BLACK_KING,
        }
    }

    pub fn valid_move_types(kind: PieceType) -> HashSet<MoveType> {
        use MoveAmount::*;
        use PieceType::*;

        match kind {
            Pawn(Some(k)) => Self::valid_move_types(*k),
            Pawn(None) => HashSet::from([
                MoveType::Diagonal(One),
                MoveType::Vertical(One),
                MoveType::Vertical(Two),
                MoveType::EnPassant,
            ]),
            Knight => HashSet::from([MoveType::Knight]),
            Bishop(_) => HashSet::from([MoveType::Diagonal(Many)]),
            Rook => HashSet::from([
                MoveType::Horizontal(Many),
                MoveType::Vertical(Many),
                MoveType::KingSideCastle,
                MoveType::QueenSideCastle,
            ]),
            Queen => HashSet::from([
                MoveType::Horizontal(Many),
                MoveType::Vertical(Many),
                MoveType::Diagonal(Many),
            ]),
            King => HashSet::from([
                MoveType::Horizontal(One),
                MoveType::Vertical(One),
                MoveType::Diagonal(One),
                MoveType::KingSideCastle,
                MoveType::QueenSideCastle,
            ]),
        }
    }
}

trait PieceBehavior {
    fn get_valid_move_types() -> HashSet<MoveType>;
    fn get_symbol(&self) -> char;
}

pub struct Pawn {
    color: PieceColor,
    has_moved: bool,
}

pub struct Knight {
    color: PieceColor,
}

pub struct Bishop {
    color: PieceColor,
}

pub struct Rook {
    color: PieceColor,
    has_moved: bool,
}

pub struct Queen {
    color: PieceColor,
}

pub struct King {
    color: PieceColor,
    has_moved: bool,
}

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

    #[test]
    fn test_make_black_rook() {
        let piece = Piece::new(PieceColor::Black, PieceType::Rook);
        assert_eq!(piece.symbol, BLACK_ROOK);
        assert_eq!(piece.kind, PieceType::Rook);
        assert_eq!(piece.color, PieceColor::Black);
    }

    #[test]
    fn test_get_white_knight_char() {
        assert_eq!(
            Piece::get_symbol(PieceColor::White, PieceType::Knight),
            WHITE_KNIGHT
        );
    }

    #[test]
    fn test_get_promoted_white_pawn_queen() {
        assert_eq!(
            Piece::get_symbol(
                PieceColor::White,
                PieceType::Pawn(Some(Box::new(PieceType::Queen)))
            ),
            WHITE_QUEEN
        );
    }
}