use core::fmt;

use crate::{
    bitboard::{have_common_bit, square_to_bitboard},
    board::{Board, Color, Kind, Piece},
    square::{coords_to_square, square_to_algebraic, Square},
    state::{Castle, State},
};

#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
pub enum Promote {
    Knight,
    Rook,
    Bishop,
    Queen,
}

#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
pub enum MoveType {
    Quiet,
    Capture,
    DoublePush,
    Promotion(Promote),
    PromotionCapture(Promote),
    EnPassant,
    Castle,
}

#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
pub struct Move {
    pub src: usize,
    pub dst: usize,
    pub move_type: MoveType,
}

impl fmt::Debug for Move {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(
            f,
            "{}{}",
            square_to_algebraic(self.src),
            square_to_algebraic(self.dst)
        )?;

        if let MoveType::Promotion(piece) | MoveType::PromotionCapture(piece) = &self.move_type {
            let promote_char = match piece {
                Promote::Knight => 'n',
                Promote::Bishop => 'b',
                Promote::Rook => 'r',
                Promote::Queen => 'q',
            };
            write!(f, "{}", promote_char)?;
        }

        Ok(())
    }
}

impl Move {
    pub const fn new(src: usize, dst: usize) -> Self {
        Self {
            src,
            dst,
            move_type: MoveType::Quiet,
        }
    }

    pub const fn new_with_type(src: usize, dst: usize, move_type: MoveType) -> Self {
        Self {
            src,
            dst,
            move_type,
        }
    }

    pub fn parse_from_str(mv: &str) -> Result<Self, String> {
        if mv.len() != 4 && mv.len() != 5 {
            return Err("Invalid move characters length".to_string());
        }

        let mut mv_chars = mv.chars();
        let src_file = (mv_chars.next().unwrap() as usize) - ('a' as usize);
        let src_rank = (mv_chars.next().unwrap() as usize) - ('1' as usize);
        let dst_file = (mv_chars.next().unwrap() as usize) - ('a' as usize);
        let dst_rank = (mv_chars.next().unwrap() as usize) - ('1' as usize);

        let src = coords_to_square(src_rank, src_file);
        let dst = coords_to_square(dst_rank, dst_file);

        if mv.len() == 5 {
            let promotion_move = match mv_chars.next().unwrap() {
                'n' => Self::new_with_type(src, dst, MoveType::Promotion(Promote::Knight)),
                'b' => Self::new_with_type(src, dst, MoveType::Promotion(Promote::Bishop)),
                'r' => Self::new_with_type(src, dst, MoveType::Promotion(Promote::Rook)),
                'q' => Self::new_with_type(src, dst, MoveType::Promotion(Promote::Queen)),
                _ => return Err("Unrecongisable character in promotion piece index".to_string()),
            };

            return Ok(promotion_move);
        }

        Ok(Self::new(src, dst))
    }

    pub fn parse_into_str(&self) -> String {
        format!("{:?}", self)
    }
}

impl Board {
    pub fn make_move(&mut self, mv: &Move, color: Color) {
        self.update_board_state(mv, color);
    }

    pub fn update_board_state(&mut self, mv: &Move, color: Color) {
        let (own_pieces, opponent_pieces, en_passant_square) = match color {
            Color::White => (
                &mut self.white_pieces,
                &mut self.black_pieces,
                Some(mv.src + 8),
            ),
            Color::Black => (
                &mut self.black_pieces,
                &mut self.white_pieces,
                Some(mv.src - 8),
            ),
        };
        let pawn_move = Self::is_pawn_move(mv.src, &own_pieces[Kind::Pawn]);

        Self::update_game_state(&mut self.state, mv, color, pawn_move);

        match &mv.move_type {
            MoveType::Quiet => {
                Self::move_piece(mv.src, mv.dst, own_pieces);
            }
            MoveType::Capture => {
                Self::move_piece(mv.src, mv.dst, own_pieces);
                Self::remove_piece(mv.dst, opponent_pieces);
            }
            MoveType::EnPassant => {
                Self::move_piece(mv.src, mv.dst, own_pieces);
                Self::remove_pawn_enpassant(mv.dst, opponent_pieces, color);
            }
            MoveType::DoublePush => {
                Self::move_piece(mv.src, mv.dst, own_pieces);
                self.state.set_en_passant_target_square(en_passant_square);
            }
            MoveType::Promotion(promote) => {
                Self::remove_piece(mv.src, own_pieces);
                Self::promote_piece(mv.dst, own_pieces, promote);
            }
            MoveType::PromotionCapture(promote) => {
                Self::remove_piece(mv.src, own_pieces);
                Self::remove_piece(mv.dst, opponent_pieces);
                Self::promote_piece(mv.dst, own_pieces, promote);
            }
            MoveType::Castle => {
                Self::move_piece(mv.src, mv.dst, own_pieces);
                Self::move_rook_castle(mv.dst, own_pieces);
                self.state.set_castling_ability(color, Castle::None)
            }
        }
    }

    fn update_game_state(state: &mut State, mv: &Move, color: Color, pawn_move: bool) {
        state.set_en_passant_target_square(None);
        state.update_castling_state_quiet(mv.src, color);
        state.update_castling_state_capture(mv.dst, Color::opponent_color(color));
        state.update_half_move(mv.move_type, pawn_move);
        state.update_full_move(color);
        state.change_side();
    }

    fn move_piece(src: usize, dst: usize, pieces: &mut [Piece; 6]) {
        for p in pieces.iter_mut() {
            if have_common_bit(p.bitboard, square_to_bitboard(src)) {
                p.bitboard &= !square_to_bitboard(src);
                p.bitboard |= square_to_bitboard(dst);
                break;
            }
        }
    }

    fn move_rook_castle(king_dst: usize, pieces: &mut [Piece; 6]) {
        let (rook_src, rook_dst) = match king_dst {
            Square::C1 | Square::C8 => (king_dst - 2, king_dst + 1),
            Square::G1 | Square::G8 => (king_dst + 1, king_dst - 1),
            _ => return,
        };

        Self::move_piece(rook_src, rook_dst, pieces);
    }

    fn promote_piece(square: usize, pieces: &mut [Piece; 6], promote: &Promote) {
        match promote {
            Promote::Knight => pieces[Kind::Knight].bitboard |= square_to_bitboard(square),
            Promote::Bishop => pieces[Kind::Bishop].bitboard |= square_to_bitboard(square),
            Promote::Rook => pieces[Kind::Rook].bitboard |= square_to_bitboard(square),
            Promote::Queen => pieces[Kind::Queen].bitboard |= square_to_bitboard(square),
        };
    }

    fn remove_piece(square: usize, pieces: &mut [Piece; 6]) {
        for p in pieces.iter_mut() {
            if have_common_bit(p.bitboard, square_to_bitboard(square)) {
                p.bitboard &= !(square_to_bitboard(square));
                break;
            }
        }
    }

    fn remove_pawn_enpassant(square: usize, pieces: &mut [Piece; 6], color: Color) {
        let piece_to_remove = match color {
            Color::White => square - 8,
            Color::Black => square + 8,
        };

        Self::remove_piece(piece_to_remove, pieces);
    }

    const fn is_pawn_move(square: usize, pawns: &Piece) -> bool {
        have_common_bit(square_to_bitboard(square), pawns.bitboard)
    }
}

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

    const FEN_QUIET: [&str; 2] = [
        "r3k2r/2p1p1qp/2npb3/1p3p2/p3P1pP/P1PB1Q2/1P1PNPP1/R3K2R w KQkq - 0 1",
        "r3k2r/2p1p1qp/2npb3/1p3p2/pP2P1pP/P1PB1Q2/3PNPP1/R3K2R b KQkq b3 0 1",
    ];

    #[test]
    fn test_make_move_quiet() -> Result<(), String> {
        let mut game = from_fen(FEN_QUIET[0])?;
        let mv = Move::new_with_type(9, 25, MoveType::DoublePush);
        game.board.make_move(&mv, Color::White);
        assert_eq!(game, from_fen(FEN_QUIET[1])?);

        Ok(())
    }

    const FEN_CAPTURE: [&str; 2] = [
        "r3k2r/2p1p1qp/2npb3/1p3p2/p3P1pP/P1PB1Q2/1P1PNPP1/R3K2R w KQkq - 0 1",
        "r3k2r/2p1p1qp/2npb3/1p3Q2/p3P1pP/P1PB4/1P1PNPP1/R3K2R b KQkq - 0 1",
    ];

    #[test]
    fn test_make_move_capture() -> Result<(), String> {
        let mut game = from_fen(FEN_CAPTURE[0])?;
        let mv = Move::new_with_type(21, 37, MoveType::Capture);
        game.board.make_move(&mv, Color::White);
        assert_eq!(game, from_fen(FEN_CAPTURE[1])?);

        Ok(())
    }

    const FEN_EN_PASSANT: [&str; 2] = [
        "r3k2r/2p1p1qp/2npb3/1p3p2/p3P1pP/P1PB1Q2/1P1PNPP1/R3K2R b KQkq h3 0 1",
        "r3k2r/2p1p1qp/2npb3/1p3p2/p3P3/P1PB1Q1p/1P1PNPP1/R3K2R w KQkq - 0 2",
    ];

    #[test]
    fn test_make_move_en_passant() -> Result<(), String> {
        let mut game = from_fen(FEN_EN_PASSANT[0])?;
        let mv = Move::new_with_type(30, 23, MoveType::EnPassant);
        game.board.make_move(&mv, Color::Black);
        assert_eq!(game, from_fen(FEN_EN_PASSANT[1])?);

        Ok(())
    }

    const FEN_DOUBLE_PUSH: [&str; 2] = [
        "rnbqkbnr/p1pppppp/8/8/1p5P/8/PPPPPPP1/RNBQKBNR w KQkq - 0 1",
        "rnbqkbnr/p1pppppp/8/8/1pP4P/8/PP1PPPP1/RNBQKBNR b KQkq c3 0 1",
    ];

    #[test]
    fn test_make_move_double_push() -> Result<(), String> {
        let mut game = from_fen(FEN_DOUBLE_PUSH[0])?;
        let mv = Move::new_with_type(10, 26, MoveType::DoublePush);
        game.board.make_move(&mv, Color::White);
        assert_eq!(game, from_fen(FEN_DOUBLE_PUSH[1])?);
        Ok(())
    }

    const FEN_PROMOTION: [&str; 2] = [
        "8/6P1/4n2b/1p6/1Kp5/6n1/4b3/1k6 w - - 0 1",
        "6Q1/8/4n2b/1p6/1Kp5/6n1/4b3/1k6 b - - 0 1",
    ];

    #[test]
    fn test_make_move_promotion() -> Result<(), String> {
        let mut game = from_fen(FEN_PROMOTION[0])?;
        let mv = Move::new_with_type(54, 62, MoveType::Promotion(Promote::Queen));
        game.board.make_move(&mv, Color::White);
        assert_eq!(game, from_fen(FEN_PROMOTION[1])?);

        Ok(())
    }

    const FEN_PROMOTION_CAPTURE: [&str; 2] = [
        "5n2/6P1/7b/1p6/1Kp5/6n1/4b3/1k6 w - - 0 1",
        "5Q2/8/7b/1p6/1Kp5/6n1/4b3/1k6 b - - 0 1",
    ];

    #[test]
    fn test_make_move_promotion_capture() -> Result<(), String> {
        let mut game = from_fen(FEN_PROMOTION_CAPTURE[0])?;
        let mv = Move::new_with_type(54, 61, MoveType::PromotionCapture(Promote::Queen));
        game.board.make_move(&mv, Color::White);
        assert_eq!(game, from_fen(FEN_PROMOTION_CAPTURE[1])?);

        Ok(())
    }

    const FEN_CASTLE: [&str; 2] = [
        "r3k2r/2p1p1qp/2npb3/1p3p2/p3P1pP/P1PB1Q2/1P1PNPP1/R3K2R w KQkq - 0 1",
        "r3k2r/2p1p1qp/2npb3/1p3p2/p3P1pP/P1PB1Q2/1P1PNPP1/R4RK1 b kq - 1 1",
    ];

    #[test]
    fn test_make_move_castle() -> Result<(), String> {
        let mut game = from_fen(FEN_CASTLE[0])?;
        let mv = Move::new_with_type(4, 6, MoveType::Castle);
        game.board.make_move(&mv, Color::White);
        assert_eq!(game, from_fen(FEN_CASTLE[1])?);
        Ok(())
    }

    #[test]
    fn test_parse_from_str() -> Result<(), String> {
        let mv_str = "a1a8";
        let actual = Move::parse_from_str(&mv_str)?;
        let expected = Move::new(Square::A1, Square::A8);
        assert_eq!(actual, expected);

        let mv_str = "b7b8q";
        let actual = Move::parse_from_str(&mv_str)?;
        let expected =
            Move::new_with_type(Square::B7, Square::B8, MoveType::Promotion(Promote::Queen));
        assert_eq!(actual, expected);

        Ok(())
    }

    #[test]
    #[should_panic(expected = "Invalid move characters length")]
    fn test_parse_from_str_panic() -> () {
        Move::parse_from_str(&"a7a8qk").unwrap();
    }
}