use u64 as Bitboard;

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

#[derive(Debug, PartialEq, Eq, Clone)]
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, Kind::Pawn, Color::White),
                Piece::new(0x42, Kind::Knight, Color::White),
                Piece::new(0x24, Kind::Bishop, Color::White),
                Piece::new(0x81, Kind::Rook, Color::White),
                Piece::new(0x8, Kind::Queen, Color::White),
                Piece::new(0x10, Kind::King, Color::White),
            ],
            black_pieces: [
                Piece::new(0xff000000000000, Kind::Pawn, Color::Black),
                Piece::new(0x4200000000000000, Kind::Knight, Color::Black),
                Piece::new(0x2400000000000000, Kind::Bishop, Color::Black),
                Piece::new(0x8100000000000000, Kind::Rook, Color::Black),
                Piece::new(0x800000000000000, Kind::Queen, Color::Black),
                Piece::new(0x1000000000000000, Kind::King, Color::Black),
            ],
            state: State::new(),
        }
    }

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

        have_common_bit(
            opponent[Kind::Pawn].bitboard,
            fetch_pawn_attacks(square, own_color),
        ) || have_common_bit(
            opponent[Kind::Knight].bitboard,
            fetch_knight_attacks(square),
        ) || have_common_bit(
            opponent[Kind::Bishop].bitboard,
            fetch_bishop_attacks(all_occupancies, square),
        ) || have_common_bit(
            opponent[Kind::Rook].bitboard,
            fetch_rook_attacks(all_occupancies, square),
        ) || have_common_bit(
            opponent[Kind::Queen].bitboard,
            fetch_queen_attacks(all_occupancies, square),
        ) || have_common_bit(opponent[Kind::King].bitboard, fetch_king_attacks(square))
    }

    pub fn is_move_legit(&self, square: usize, opponent_color: Color) -> bool {
        !self.is_attacked(square, opponent_color)
    }

    pub fn pseudo_moves_all(&self, color: Color) -> Vec<Move> {
        let mut moves = vec![];
        moves.extend(self.pseudo_moves(color, Kind::Pawn));
        moves.extend(self.pseudo_moves(color, Kind::Knight));
        moves.extend(self.pseudo_moves(color, Kind::Bishop));
        moves.extend(self.pseudo_moves(color, Kind::Rook));
        moves.extend(self.pseudo_moves(color, Kind::Queen));
        moves.extend(self.pseudo_moves(color, Kind::King));
        moves
    }

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

        match kind {
            Kind::Pawn => pawn_pseudo_moves(
                pieces,
                all_occupancies,
                opponent_occupancies,
                self.state.en_passant_target_square(),
                color,
            ),
            Kind::Knight => knight_pseudo_moves(pieces, all_occupancies, own_occupancies),
            Kind::Bishop => bishop_pseudo_moves(pieces, all_occupancies, own_occupancies),
            Kind::Rook => rook_pseudo_moves(pieces, all_occupancies, own_occupancies),
            Kind::Queen => queen_pseudo_moves(pieces, all_occupancies, own_occupancies),
            Kind::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.kind].bitboard |= piece.bitboard,
            Color::White => self.white_pieces[piece.kind].bitboard |= piece.bitboard,
        };
    }

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

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

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

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

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

impl Kind {
    fn idx(&self) -> usize {
        match self {
            Kind::Pawn => 0,
            Kind::Knight => 1,
            Kind::Bishop => 2,
            Kind::Rook => 3,
            Kind::Queen => 4,
            Kind::King => 5,
        }
    }
}
use std::ops::{Index, IndexMut};

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

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

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

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

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

#[cfg(test)]
mod tests {
    use crate::{attack::init_attacks, fen::from_fen};

    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(())
    }

    #[test]
    fn test_fifty_move_draw() -> Result<(), String> {
        //TODO: make a MoveHistory/BoardHistory/GameHistory struct
        Ok(())
    }

    #[test]
    fn test_threefold_repetition() -> Result<(), String> {
        //TODO: make a MoveHistory/BoardHistory/GameHistory struct
        Ok(())
    }
}