use u64 as Bitboard;

use crate::board::bitboard::{have_common_bit, lsb};
use crate::board::state::State;
use crate::movegen::attack_generator::{
    fetch_bishop_attacks, fetch_king_attacks, fetch_knight_attacks, fetch_pawn_attacks,
    fetch_queen_attacks, fetch_rook_attacks,
};
use crate::movegen::move_generator::{
    bishop_pseudo_moves, king_pseudo_moves, knight_pseudo_moves, pawn_pseudo_moves,
    queen_pseudo_moves, rook_pseudo_moves,
};
use crate::movegen::r#move::{Move, Promote};

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Board {
    pub white_pieces: [Piece; 6],
    pub black_pieces: [Piece; 6],
    pub state: State,
}

impl Board {
    pub const fn new() -> Self {
        Self {
            white_pieces: [
                Piece::new(0xff00, PieceType::Pawn, Color::White),
                Piece::new(0x42, PieceType::Knight, Color::White),
                Piece::new(0x24, PieceType::Bishop, Color::White),
                Piece::new(0x81, PieceType::Rook, Color::White),
                Piece::new(0x8, PieceType::Queen, Color::White),
                Piece::new(0x10, PieceType::King, Color::White),
            ],
            black_pieces: [
                Piece::new(0xff000000000000, PieceType::Pawn, Color::Black),
                Piece::new(0x4200000000000000, PieceType::Knight, Color::Black),
                Piece::new(0x2400000000000000, PieceType::Bishop, Color::Black),
                Piece::new(0x8100000000000000, PieceType::Rook, Color::Black),
                Piece::new(0x800000000000000, PieceType::Queen, Color::Black),
                Piece::new(0x1000000000000000, PieceType::King, Color::Black),
            ],
            state: State::new(),
        }
    }

    pub const fn empty_board() -> Self {
        Self {
            white_pieces: [
                Piece::new(0x0, PieceType::Pawn, Color::White),
                Piece::new(0x0, PieceType::Knight, Color::White),
                Piece::new(0x0, PieceType::Bishop, Color::White),
                Piece::new(0x0, PieceType::Rook, Color::White),
                Piece::new(0x0, PieceType::Queen, Color::White),
                Piece::new(0x0, PieceType::King, Color::White),
            ],
            black_pieces: [
                Piece::new(0x0, PieceType::Pawn, Color::Black),
                Piece::new(0x0, PieceType::Knight, Color::Black),
                Piece::new(0x0, PieceType::Bishop, Color::Black),
                Piece::new(0x0, PieceType::Rook, Color::Black),
                Piece::new(0x0, PieceType::Queen, Color::Black),
                Piece::new(0x0, PieceType::King, Color::Black),
            ],
            state: State::new(),
        }
    }

    pub fn white_occupancies(&self) -> Bitboard {
        self.white_pieces.iter().fold(0, |acc, p| p.bitboard | acc)
    }

    pub fn black_occupancies(&self) -> Bitboard {
        self.black_pieces.iter().fold(0, |acc, p| p.bitboard | acc)
    }

    pub fn all_occupancies(&self) -> Bitboard {
        self.white_occupancies() | self.black_occupancies()
    }

    pub fn is_attacked(&self, square: usize, opponent_color: Color) -> bool {
        let all_occupancies = self.all_occupancies();
        let (opponent, own_color) = match opponent_color {
            Color::Black => (&self.black_pieces, Color::White),
            Color::White => (&self.white_pieces, Color::Black),
        };

        let pawns = opponent[PieceType::Pawn].bitboard;
        let knights = opponent[PieceType::Knight].bitboard;
        let bishops = opponent[PieceType::Bishop].bitboard;
        let rooks = opponent[PieceType::Rook].bitboard;
        let queens = opponent[PieceType::Queen].bitboard;
        let king = opponent[PieceType::King].bitboard;

        have_common_bit(pawns, fetch_pawn_attacks(square, own_color))
            || have_common_bit(knights, fetch_knight_attacks(square))
            || have_common_bit(bishops, fetch_bishop_attacks(all_occupancies, square))
            || have_common_bit(rooks, fetch_rook_attacks(all_occupancies, square))
            || have_common_bit(queens, fetch_queen_attacks(all_occupancies, square))
            || have_common_bit(king, fetch_king_attacks(square))
    }

    pub fn king_under_check(&self, color: Color) -> bool {
        let own_king_square = match color {
            Color::White => lsb(self.white_pieces[PieceType::King].bitboard),
            Color::Black => lsb(self.black_pieces[PieceType::King].bitboard),
        };

        self.is_attacked(own_king_square, color.opponent())
    }

    pub fn pseudo_moves_all(&self) -> Vec<Move> {
        let color = self.state.current_player();
        let mut moves = vec![];

        moves.extend(self.pseudo_moves(color, PieceType::Pawn));
        moves.extend(self.pseudo_moves(color, PieceType::Knight));
        moves.extend(self.pseudo_moves(color, PieceType::Bishop));
        moves.extend(self.pseudo_moves(color, PieceType::Rook));
        moves.extend(self.pseudo_moves(color, PieceType::Queen));
        moves.extend(self.pseudo_moves(color, PieceType::King));
        moves
    }

    pub fn pseudo_moves(&self, color: Color, piece_type: PieceType) -> Vec<Move> {
        let all_occupancies = self.all_occupancies();
        let (pieces, opponent_occupancies, own_occupancies) = match color {
            Color::White => (
                self.white_pieces[piece_type].bitboard,
                self.black_occupancies(),
                self.white_occupancies(),
            ),
            Color::Black => (
                self.black_pieces[piece_type].bitboard,
                self.white_occupancies(),
                self.black_occupancies(),
            ),
        };

        match piece_type {
            PieceType::Pawn => pawn_pseudo_moves(
                pieces,
                all_occupancies,
                opponent_occupancies,
                self.state.en_passant_square(),
                color,
            ),
            PieceType::Knight => knight_pseudo_moves(pieces, all_occupancies, own_occupancies),
            PieceType::Bishop => bishop_pseudo_moves(pieces, all_occupancies, own_occupancies),
            PieceType::Rook => rook_pseudo_moves(pieces, all_occupancies, own_occupancies),
            PieceType::Queen => queen_pseudo_moves(pieces, all_occupancies, own_occupancies),
            PieceType::King => {
                king_pseudo_moves(pieces, all_occupancies, own_occupancies, self, color)
            }
        }
    }

    pub fn set_piece(&mut self, piece: &Piece) {
        match piece.color {
            Color::Black => self.black_pieces[piece.piece_type].bitboard |= piece.bitboard,
            Color::White => self.white_pieces[piece.piece_type].bitboard |= piece.bitboard,
        };
    }

    pub fn set_state(&mut self, state: State) {
        self.state = state;
    }

    pub fn update_game_state(
        state: &mut State,
        mv: &Move,
        color: Color,
        pawn_move: bool,
        en_passant_square: Option<usize>,
    ) {
        state.set_en_passant_square(en_passant_square);
        state.update_castling_state_quiet(mv.src, color);
        state.update_castling_state_capture(mv.dst, color.opponent());
        state.update_half_move(mv.move_type, pawn_move);
        state.update_full_move(color);
        state.change_side();
    }

    pub fn move_piece(&mut self, src: usize, dst: usize) {
        let pieces = self.own_pieces();
        pieces
            .iter_mut()
            .filter(|p| have_common_bit(p.bitboard, square_to_bitboard(src)))
            .for_each(|p| {
                p.bitboard &= !square_to_bitboard(src);
                p.bitboard |= square_to_bitboard(dst);
            });

        //TODO:
        // pieces[piece_type].bitboard &= !square_to_bitboard(src);
        // pieces[piece_type].bitboard |= square_to_bitboard(dst);
    }

    pub fn remove_own_piece(&mut self, square: usize) {
        let pieces = self.own_pieces();
        pieces
            .iter_mut()
            .filter(|p| have_common_bit(p.bitboard, square_to_bitboard(square)))
            .for_each(|p| {
                p.bitboard &= !square_to_bitboard(square);
            });
    }

    pub fn remove_opponent_piece(&mut self, square: usize) {
        let pieces = self.opponent_pieces();
        pieces
            .iter_mut()
            .filter(|p| have_common_bit(p.bitboard, square_to_bitboard(square)))
            .for_each(|p| {
                p.bitboard &= !square_to_bitboard(square);
            });
    }

    pub fn promote_piece(&mut self, square: usize, promote: &Promote) {
        let pieces = self.own_pieces();
        match promote {
            Promote::Knight => pieces[PieceType::Knight].bitboard |= square_to_bitboard(square),
            Promote::Bishop => pieces[PieceType::Bishop].bitboard |= square_to_bitboard(square),
            Promote::Rook => pieces[PieceType::Rook].bitboard |= square_to_bitboard(square),
            Promote::Queen => pieces[PieceType::Queen].bitboard |= square_to_bitboard(square),
        };
    }

    pub fn is_pawn_move(&mut self, square: usize) -> bool {
        let pieces = self.own_pieces();
        have_common_bit(square_to_bitboard(square), pieces[PieceType::Pawn].bitboard)
    }

    pub fn own_pieces(&mut self) -> &mut [Piece; 6] {
        match self.state.current_player() {
            Color::White => &mut self.white_pieces,
            Color::Black => &mut self.black_pieces,
        }
    }

    pub fn opponent_pieces(&mut self) -> &mut [Piece; 6] {
        match self.state.current_player() {
            Color::White => &mut self.black_pieces,
            Color::Black => &mut self.white_pieces,
        }
    }

    pub fn all_pieces(&mut self) -> (&mut [Piece; 6], &mut [Piece; 6]) {
        match self.state.current_player() {
            Color::White => (&mut self.white_pieces, &mut self.black_pieces),
            Color::Black => (&mut self.black_pieces, &mut self.white_pieces),
        }
    }
}

impl Default for Board {
    fn default() -> Self {
        Self::new()
    }
}

#[derive(Debug, PartialEq, Eq, Clone)]
pub struct Piece {
    pub bitboard: Bitboard,
    pub piece_type: PieceType,
    pub color: Color,
}

impl Piece {
    pub const fn new(bitboard: Bitboard, piece_type: PieceType, color: Color) -> Self {
        Self {
            bitboard,
            piece_type,
            color,
        }
    }
}

#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub enum PieceType {
    Pawn,
    Knight,
    Bishop,
    Rook,
    Queen,
    King,
}

impl PieceType {
    pub const fn idx(self) -> usize {
        self as usize
    }
}
use std::ops::{Index, IndexMut};

use super::bitboard::square_to_bitboard;

impl Index<PieceType> for [Piece] {
    type Output = Piece;

    fn index(&self, piece_type: PieceType) -> &Self::Output {
        &self[piece_type.idx()]
    }
}

impl IndexMut<PieceType> for [Piece] {
    fn index_mut(&mut self, piece_type: PieceType) -> &mut Self::Output {
        &mut self[piece_type.idx()]
    }
}

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

impl Color {
    pub const fn opponent(self) -> Self {
        match self {
            Self::White => Self::Black,
            Self::Black => Self::White,
        }
    }
}

#[cfg(test)]
mod tests {
    use crate::{
        board::{fen::from_fen, square::Square},
        movegen::{attack_generator::init_attacks, r#move::MoveType},
    };

    use super::*;

    const FEN_EXAMPLE: [&str; 1] = ["8/6P1/4n2b/1p6/1Kp5/6n1/4b3/1k6 w - - 0 1"];

    #[test]
    fn test_occupancies() -> Result<(), String> {
        let new_game = from_fen(FEN_EXAMPLE[0])?;

        assert_eq!(new_game.board.white_occupancies(), 0x40000002000000);
        assert_eq!(new_game.board.black_occupancies(), 0x900204401002);
        assert_eq!(new_game.board.all_occupancies(), 0x40900206401002);

        Ok(())
    }

    #[test]
    fn test_is_attacked() -> Result<(), String> {
        let new_game = from_fen(FEN_EXAMPLE[0])?;
        init_attacks();

        assert!(new_game.board.is_attacked(54, Color::Black));

        Ok(())
    }

    const FEN: &str = "1r2k2r/2P1pq1p/2npb3/1p3ppP/p3P3/P2B1Q2/1P1PNPP1/R3K2R w KQk g6 0 1";
    const FEN_QUIET: &str = "1r2k2r/2P1pq1p/2npb3/1p3ppP/p3P3/P2BQ3/1P1PNPP1/R3K2R b KQk - 1 1";

    #[test]
    fn test_make_move_quiet() -> Result<(), String> {
        let mut game = from_fen(FEN)?;
        let b1c3 = Move::new(Square::F3, Square::E3);
        game.make_move(&b1c3);

        assert_eq!(game, from_fen(FEN_QUIET)?);

        Ok(())
    }

    const FEN_CAPTURE: &str = "1r2k2r/2P1pq1p/2npb3/1p3QpP/p3P3/P2B4/1P1PNPP1/R3K2R b KQk - 0 1";

    #[test]
    fn test_make_move_capture() -> Result<(), String> {
        let mut game = from_fen(FEN)?;
        let f3f5 = Move::new_with_type(Square::F3, Square::F5, MoveType::Capture);
        game.make_move(&f3f5);

        assert_eq!(game, from_fen(FEN_CAPTURE)?);

        Ok(())
    }

    const FEN_EN_PASSANT: &str =
        "1r2k2r/2P1pq1p/2npb1P1/1p3p2/p3P3/P2B1Q2/1P1PNPP1/R3K2R b KQk - 0 1";

    #[test]
    fn test_make_move_en_passant() -> Result<(), String> {
        let mut game = from_fen(FEN)?;
        let h5g6 = Move::new_with_type(Square::H5, Square::G6, MoveType::EnPassant);
        game.make_move(&h5g6);

        assert_eq!(game, from_fen(FEN_EN_PASSANT)?);

        Ok(())
    }

    const FEN_DOUBLE_PUSH: &str =
        "1r2k2r/2P1pq1p/2npb3/1p3ppP/pP2P3/P2B1Q2/3PNPP1/R3K2R b KQk b3 0 1";

    #[test]
    fn test_make_move_double_push() -> Result<(), String> {
        let mut game = from_fen(FEN)?;
        let b2b4 = Move::new_with_type(Square::B2, Square::B4, MoveType::DoublePush);
        game.make_move(&b2b4);
        assert_eq!(game, from_fen(FEN_DOUBLE_PUSH)?);

        Ok(())
    }

    const FEN_PROMOTION: &str = "1rQ1k2r/4pq1p/2npb3/1p3ppP/p3P3/P2B1Q2/1P1PNPP1/R3K2R b KQk - 0 1";

    #[test]
    fn test_make_move_promotion() -> Result<(), String> {
        let mut game = from_fen(FEN)?;
        let c7c8 = Move::new_with_type(Square::C7, Square::C8, MoveType::Promotion(Promote::Queen));
        game.make_move(&c7c8);
        assert_eq!(game, from_fen(FEN_PROMOTION)?);

        Ok(())
    }

    const FEN_PROMOTION_CAPTURE: &str =
        "1Q2k2r/4pq1p/2npb3/1p3ppP/p3P3/P2B1Q2/1P1PNPP1/R3K2R b KQk - 0 1";

    #[test]
    fn test_make_move_promotion_capture() -> Result<(), String> {
        let mut game = from_fen(FEN)?;
        let c7b8 = Move::new_with_type(
            Square::C7,
            Square::B8,
            MoveType::PromotionCapture(Promote::Queen),
        );
        game.make_move(&c7b8);
        assert_eq!(game, from_fen(FEN_PROMOTION_CAPTURE)?);

        Ok(())
    }

    const FEN_CASTLE: &str = "1r2k2r/2P1pq1p/2npb3/1p3ppP/p3P3/P2B1Q2/1P1PNPP1/R4RK1 b k - 1 1";

    #[test]
    fn test_make_move_castle() -> Result<(), String> {
        let mut game = from_fen(FEN)?;
        let e1g1 = Move::new_with_type(Square::E1, Square::G1, MoveType::Castle);
        game.make_move(&e1g1);
        assert_eq!(game, from_fen(FEN_CASTLE)?);
        Ok(())
    }
}