-/// move_from_san() takes a position and a string as input, and tries to
-/// interpret the string as a move in short algebraic notation. On success,
-/// the move is returned. On failure (i.e. if the string is unparsable, or
-/// if the move is illegal or ambiguous), MOVE_NONE is returned.
-
-Move move_from_san(const Position& pos, const string& movestr) {
-
- assert(pos.is_ok());
-
- enum { START, TO_FILE, TO_RANK, PROMOTION_OR_CHECK, PROMOTION, CHECK, END };
- static const string pieceLetters = "KQRBN";
-
- MoveStack mlist[MOVES_MAX], *last;
- PieceType pt = PIECE_TYPE_NONE, promotion = PIECE_TYPE_NONE;
- File fromFile = FILE_NONE, toFile = FILE_NONE;
- Rank fromRank = RANK_NONE, toRank = RANK_NONE;
- Move move = MOVE_NONE;
- Square from, to;
- int matches, state = START;
-
- // Generate all legal moves for the given position
- last = generate<MV_LEGAL>(pos, mlist);
-
- // Castling moves
- if (movestr == "O-O-O" || movestr == "O-O-O+")
- {
- for (MoveStack* cur = mlist; cur != last; cur++)
- if (move_is_long_castle(cur->move))
- return cur->move;
-
- return MOVE_NONE;
- }
- else if (movestr == "O-O" || movestr == "O-O+")
- {
- for (MoveStack* cur = mlist; cur != last; cur++)
- if (move_is_short_castle(cur->move))
- return cur->move;
-
- return MOVE_NONE;
- }
-
- // Normal moves. We use a simple FSM to parse the san string
- for (size_t i = 0; i < movestr.length(); i++)
- {
- char type, c = movestr[i];
-
- if (pieceLetters.find(c) != string::npos)
- type = 'P';
- else if (c >= 'a' && c <= 'h')
- type = 'F';
- else if (c >= '1' && c <= '8')
- type = 'R';
- else
- type = c;
-
- switch (type) {
- case 'P':
- if (state == START)
- {
- pt = piece_type_from_char(c);
- state = TO_FILE;
- }
- else if (state == PROMOTION)
- {
- promotion = piece_type_from_char(c);
- state = (i < movestr.length() - 1 ? CHECK : END);
- }
- else
- return MOVE_NONE;
- break;
- case 'F':
- if (state == START)
- {
- pt = PAWN;
- fromFile = toFile = file_from_char(c);
- state = TO_RANK;
- }
- else if (state == TO_FILE)
- {
- toFile = file_from_char(c);
- state = TO_RANK;
- }
- else if (state == TO_RANK && toFile != FILE_NONE)
- {
- // Previous file was for disambiguation
- fromFile = toFile;
- toFile = file_from_char(c);
- }
- else
- return MOVE_NONE;
- break;
- case 'R':
- if (state == TO_RANK)
- {
- toRank = rank_from_char(c);
- state = (i < movestr.length() - 1) ? PROMOTION_OR_CHECK : END;
- }
- else if (state == TO_FILE && fromRank == RANK_NONE)
- {
- // It's a disambiguation rank instead of a file
- fromRank = rank_from_char(c);
- }
- else
- return MOVE_NONE;
- break;
- case 'x':
- case 'X':
- if (state == TO_RANK)
- {
- // Previous file was for disambiguation, or it's a pawn capture
- fromFile = toFile;
- state = TO_FILE;
- }
- else if (state != TO_FILE)
- return MOVE_NONE;
- break;
- case '=':
- if (state == PROMOTION_OR_CHECK)
- state = PROMOTION;
- else
- return MOVE_NONE;
- break;
- case '+':
- case '#':
- if (state == PROMOTION_OR_CHECK || state == CHECK)
- state = END;
- else
- return MOVE_NONE;
- break;
- default:
- return MOVE_NONE;
- break;
- }
- }
-
- if (state != END)
- return MOVE_NONE;
-
- // Look for an unambiguous matching move
- to = make_square(toFile, toRank);
- matches = 0;
-
- for (MoveStack* cur = mlist; cur != last; cur++)
- {
- from = move_from(cur->move);
-
- if ( pos.type_of_piece_on(from) == pt
- && move_to(cur->move) == to
- && move_promotion_piece(cur->move) == promotion
- && (fromFile == FILE_NONE || fromFile == square_file(from))
- && (fromRank == RANK_NONE || fromRank == square_rank(from)))
- {
- move = cur->move;
- matches++;
- }
- }
- return matches == 1 ? move : MOVE_NONE;
-}
-
-