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/*

  Stockfish, a UCI chess playing engine derived from Glaurung 2.1

  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)

  Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad

  Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad

  Stockfish is free software: you can redistribute it and/or modify

  it under the terms of the GNU General Public License as published by

  the Free Software Foundation, either version 3 of the License, or

  (at your option) any later version.

  Stockfish is distributed in the hope that it will be useful,

  but WITHOUT ANY WARRANTY; without even the implied warranty of

  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License

  along with this program.  If not, see <http://www.gnu.org/licenses/>.

*/

#ifndef POSITION_H_INCLUDED

#define POSITION_H_INCLUDED

#include <cassert>

#include <deque>

#include <memory> // For std::unique_ptr

#include <string>

#include "bitboard.h"

#include "types.h"

/// StateInfo struct stores information needed to restore a Position object to

/// its previous state when we retract a move. Whenever a move is made on the

/// board (by calling Position::do_move), a StateInfo object must be passed.

struct StateInfo {

  // Copied when making a move

  Key    pawnKey;

  Key    materialKey;

  Value  nonPawnMaterial[COLOR_NB];

  int    castlingRights;

  int    rule50;

  int    pliesFromNull;

  Score  psq;

  Square epSquare;

  // Not copied when making a move (will be recomputed anyhow)

  Key        key;

  Bitboard   checkersBB;

  Piece      capturedPiece;

  StateInfo* previous;

  Bitboard   blockersForKing[COLOR_NB];

  Bitboard   pinnersForKing[COLOR_NB];

  Bitboard   checkSquares[PIECE_TYPE_NB];

};

// In a std::deque references to elements are unaffected upon resizing

typedef std::unique_ptr<std::deque<StateInfo>> StateListPtr;

/// Position class stores information regarding the board representation as

/// pieces, side to move, hash keys, castling info, etc. Important methods are

/// do_move() and undo_move(), used by the search to update node info when

/// traversing the search tree.

class Thread;

class Position {

public:

  static void init();

  Position() = default;

  Position(const Position&) = delete;

  Position& operator=(const Position&) = delete;

  // FEN string input/output

  Position& set(const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th);

  const std::string fen() const;

  // Position representation

  Bitboard pieces() const;

  Bitboard pieces(PieceType pt) const;

  Bitboard pieces(PieceType pt1, PieceType pt2) const;

  Bitboard pieces(Color c) const;

  Bitboard pieces(Color c, PieceType pt) const;

  Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;

  Piece piece_on(Square s) const;

  Square ep_square() const;

  bool empty(Square s) const;

  template<PieceType Pt> int count(Color c) const;

  template<PieceType Pt> const Square* squares(Color c) const;

  template<PieceType Pt> Square square(Color c) const;

  // Castling

  int can_castle(Color c) const;

  int can_castle(CastlingRight cr) const;

  bool castling_impeded(CastlingRight cr) const;

  Square castling_rook_square(CastlingRight cr) const;

  // Checking

  Bitboard checkers() const;

  Bitboard discovered_check_candidates() const;

  Bitboard pinned_pieces(Color c) const;

  Bitboard check_squares(PieceType pt) const;

  // Attacks to/from a given square

  Bitboard attackers_to(Square s) const;

  Bitboard attackers_to(Square s, Bitboard occupied) const;

  Bitboard attacks_from(Piece pc, Square s) const;

  template<PieceType> Bitboard attacks_from(Square s) const;

  template<PieceType> Bitboard attacks_from(Square s, Color c) const;

  Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;

  // Properties of moves

  bool legal(Move m) const;

  bool pseudo_legal(const Move m) const;

  bool capture(Move m) const;

  bool capture_or_promotion(Move m) const;

  bool gives_check(Move m) const;

  bool advanced_pawn_push(Move m) const;

  Piece moved_piece(Move m) const;

  Piece captured_piece() const;

  // Piece specific

  bool pawn_passed(Color c, Square s) const;

  bool opposite_bishops() const;

  // Doing and undoing moves

  void do_move(Move m, StateInfo& st, bool givesCheck);

  void undo_move(Move m);

  void do_null_move(StateInfo& st);

  void undo_null_move();

  // Static Exchange Evaluation

  bool see_ge(Move m, Value value) const;

  // Accessing hash keys

  Key key() const;

  Key key_after(Move m) const;

  Key material_key() const;

  Key pawn_key() const;

  // Other properties of the position

  Color side_to_move() const;

  Phase game_phase() const;

  int game_ply() const;

  bool is_chess960() const;

  Thread* this_thread() const;

  uint64_t nodes_searched() const;

  bool is_draw() const;

  int rule50_count() const;

  Score psq_score() const;

  Value non_pawn_material(Color c) const;

  // Position consistency check, for debugging

  bool pos_is_ok(int* failedStep = nullptr) const;

  void flip();

private:

  // Initialization helpers (used while setting up a position)

  void set_castling_right(Color c, Square rfrom);

  void set_state(StateInfo* si) const;

  void set_check_info(StateInfo* si) const;

  // Other helpers

  void put_piece(Piece pc, Square s);

  void remove_piece(Piece pc, Square s);

  void move_piece(Piece pc, Square from, Square to);

  template<bool Do>

  void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);

  // Data members

  Piece board[SQUARE_NB];

  Bitboard byTypeBB[PIECE_TYPE_NB];

  Bitboard byColorBB[COLOR_NB];

  int pieceCount[PIECE_NB];

  Square pieceList[PIECE_NB][16];

  int index[SQUARE_NB];

  int castlingRightsMask[SQUARE_NB];

  Square castlingRookSquare[CASTLING_RIGHT_NB];

  Bitboard castlingPath[CASTLING_RIGHT_NB];

  uint64_t nodes;

  int gamePly;

  Color sideToMove;

  Thread* thisThread;

  StateInfo* st;

  bool chess960;

};

extern std::ostream& operator<<(std::ostream& os, const Position& pos);

inline Color Position::side_to_move() const {

  return sideToMove;

}

inline bool Position::empty(Square s) const {

  return board[s] == NO_PIECE;

}

inline Piece Position::piece_on(Square s) const {

  return board[s];

}

inline Piece Position::moved_piece(Move m) const {

  return board[from_sq(m)];

}

inline Bitboard Position::pieces() const {

  return byTypeBB[ALL_PIECES];

}

inline Bitboard Position::pieces(PieceType pt) const {

  return byTypeBB[pt];

}

inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {

  return byTypeBB[pt1] | byTypeBB[pt2];

}

inline Bitboard Position::pieces(Color c) const {

  return byColorBB[c];

}

inline Bitboard Position::pieces(Color c, PieceType pt) const {

  return byColorBB[c] & byTypeBB[pt];

}

inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {

  return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);

}

template<PieceType Pt> inline int Position::count(Color c) const {

  return pieceCount[make_piece(c, Pt)];

}

template<PieceType Pt> inline const Square* Position::squares(Color c) const {

  return pieceList[make_piece(c, Pt)];

}

template<PieceType Pt> inline Square Position::square(Color c) const {

  assert(pieceCount[make_piece(c, Pt)] == 1);

  return pieceList[make_piece(c, Pt)][0];

}

inline Square Position::ep_square() const {

  return st->epSquare;

}

inline int Position::can_castle(CastlingRight cr) const {

  return st->castlingRights & cr;

}

inline int Position::can_castle(Color c) const {

  return st->castlingRights & ((WHITE_OO | WHITE_OOO) << (2 * c));

}

inline bool Position::castling_impeded(CastlingRight cr) const {

  return byTypeBB[ALL_PIECES] & castlingPath[cr];

}

inline Square Position::castling_rook_square(CastlingRight cr) const {

  return castlingRookSquare[cr];

}

template<PieceType Pt>

inline Bitboard Position::attacks_from(Square s) const {

  return  Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])

        : Pt == QUEEN  ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)

        : StepAttacksBB[Pt][s];

}

template<>

inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {

  return StepAttacksBB[make_piece(c, PAWN)][s];

}

inline Bitboard Position::attacks_from(Piece pc, Square s) const {

  return attacks_bb(pc, s, byTypeBB[ALL_PIECES]);

}

inline Bitboard Position::attackers_to(Square s) const {

  return attackers_to(s, byTypeBB[ALL_PIECES]);

}

inline Bitboard Position::checkers() const {

  return st->checkersBB;

}

inline Bitboard Position::discovered_check_candidates() const {

  return st->blockersForKing[~sideToMove] & pieces(sideToMove);

}

inline Bitboard Position::pinned_pieces(Color c) const {

  return st->blockersForKing[c] & pieces(c);

}

inline Bitboard Position::check_squares(PieceType pt) const {

  return st->checkSquares[pt];

}

inline bool Position::pawn_passed(Color c, Square s) const {

  return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));

}

inline bool Position::advanced_pawn_push(Move m) const {

  return   type_of(moved_piece(m)) == PAWN

        && relative_rank(sideToMove, from_sq(m)) > RANK_4;

}

inline Key Position::key() const {

  return st->key;

}

inline Key Position::pawn_key() const {

  return st->pawnKey;

}

inline Key Position::material_key() const {

  return st->materialKey;

}

inline Score Position::psq_score() const {

  return st->psq;

}

inline Value Position::non_pawn_material(Color c) const {

  return st->nonPawnMaterial[c];

}

inline int Position::game_ply() const {

  return gamePly;

}

inline int Position::rule50_count() const {

  return st->rule50;

}

inline uint64_t Position::nodes_searched() const {

  return nodes;

}

inline bool Position::opposite_bishops() const {

  return   pieceCount[W_BISHOP] == 1

        && pieceCount[B_BISHOP] == 1

        && opposite_colors(square<BISHOP>(WHITE), square<BISHOP>(BLACK));

}

inline bool Position::is_chess960() const {

  return chess960;

}

inline bool Position::capture_or_promotion(Move m) const {

  assert(is_ok(m));

  return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));

}

inline bool Position::capture(Move m) const {

  assert(is_ok(m));

  // Castling is encoded as "king captures rook"

  return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;

}

inline Piece Position::captured_piece() const {

  return st->capturedPiece;

}

inline Thread* Position::this_thread() const {

  return thisThread;

}

inline void Position::put_piece(Piece pc, Square s) {

  board[s] = pc;

  byTypeBB[ALL_PIECES] |= s;

  byTypeBB[type_of(pc)] |= s;

  byColorBB[color_of(pc)] |= s;

  index[s] = pieceCount[pc]++;

  pieceList[pc][index[s]] = s;

  pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;

}

inline void Position::remove_piece(Piece pc, Square s) {

  // WARNING: This is not a reversible operation. If we remove a piece in

  // do_move() and then replace it in undo_move() we will put it at the end of

  // the list and not in its original place, it means index[] and pieceList[]

  // are not invariant to a do_move() + undo_move() sequence.

  byTypeBB[ALL_PIECES] ^= s;

  byTypeBB[type_of(pc)] ^= s;

  byColorBB[color_of(pc)] ^= s;

  /* board[s] = NO_PIECE;  Not needed, overwritten by the capturing one */

  Square lastSquare = pieceList[pc][--pieceCount[pc]];

  index[lastSquare] = index[s];

  pieceList[pc][index[lastSquare]] = lastSquare;

  pieceList[pc][pieceCount[pc]] = SQ_NONE;

  pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;

}

inline void Position::move_piece(Piece pc, Square from, Square to) {

  // index[from] is not updated and becomes stale. This works as long as index[]

  // is accessed just by known occupied squares.

  Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];

  byTypeBB[ALL_PIECES] ^= from_to_bb;

  byTypeBB[type_of(pc)] ^= from_to_bb;

  byColorBB[color_of(pc)] ^= from_to_bb;

  board[from] = NO_PIECE;

  board[to] = pc;

  index[to] = index[from];

  pieceList[pc][index[to]] = to;

}

#endif // #ifndef POSITION_H_INCLUDED