/*
  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
  Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, 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/>.
*/


////
//// Includes
////

#include "direction.h"
#include "square.h"


////
//// Local definitions
////

namespace {

  const SquareDelta directionToDelta[] = {
      DELTA_E, DELTA_W, DELTA_N, DELTA_S, DELTA_NE, DELTA_SW, DELTA_NW, DELTA_SE
  };

  bool reachable(Square orig, Square dest, SignedDirection dir) {

    SquareDelta delta = directionToDelta[dir];
    Square from = orig;
    Square to = from + delta;
    while (to != dest && square_distance(to, from) == 1 && square_is_ok(to))
    {
        from = to;
        to += delta;
    }
    return (to == dest && square_distance(from, to) == 1);
  }

}


////
//// Variables
////

uint8_t DirectionTable[64][64];
uint8_t SignedDirectionTable[64][64];


////
//// Functions
////

void init_direction_table() {

  for (Square s1 = SQ_A1; s1 <= SQ_H8; s1++)
      for (Square s2 = SQ_A1; s2 <= SQ_H8; s2++)
      {
          DirectionTable[s1][s2] = uint8_t(DIR_NONE);
          SignedDirectionTable[s1][s2] = uint8_t(SIGNED_DIR_NONE);
          if (s1 == s2)
              continue;

          for (SignedDirection d = SIGNED_DIR_E; d != SIGNED_DIR_NONE; d++)
          {
              if (reachable(s1, s2, d))
              {
                  SignedDirectionTable[s1][s2] = uint8_t(d);
                  DirectionTable[s1][s2] = uint8_t(d / 2);
                  break;
              }
          }
      }
}