Fix parsing of OO castling when redefined

[xboard.git] / parser.c

/*
 * parser.c --
 *
 * Copyright 2011, 2012, 2013, 2014, 2015 Free Software Foundation, Inc.
 * ------------------------------------------------------------------------
 *
 * GNU XBoard 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.
 *
 * GNU XBoard 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/.  *
 *
 *------------------------------------------------------------------------
 ** See the file ChangeLog for a revision history.  */

#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include "common.h"
#include "backend.h"
#include "frontend.h"
#include "parser.h"
#include "moves.h"


extern Board    boards[MAX_MOVES];
extern int      PosFlags(int nr);
int             yyboardindex;
int             yyskipmoves = FALSE;
char            currentMoveString[4096]; // a bit ridiculous size?
char *yy_text;

#define PARSEBUFSIZE 10000

static FILE *inputFile;
static char *inPtr, *parsePtr, *parseStart;
static char inputBuf[PARSEBUFSIZE];
static char yytext[PARSEBUFSIZE];
static char fromString = 0, lastChar = '\n';

#define NOTHING 0
#define NUMERIC 1
#define ALPHABETIC 2
#define BADNUMBER (-2000000000)

#define XCO    0
#define YCO   53
#define PIECE 94
#define MISC 155
#define JIS  200

unsigned char kanjiTab[] = {
  '1', 0357, 0274, 0221, // kanji notation for arabic digits
  '2', 0357, 0274, 0222,
  '3', 0357, 0274, 0223,
  '4', 0357, 0274, 0224,
  '5', 0357, 0274, 0225,
  '6', 0357, 0274, 0226,
  '7', 0357, 0274, 0227,
  '8', 0357, 0274, 0230,
  '9', 0357, 0274, 0231,
  'x', 0345, 0220, 0214,
  's', 0345, 0205, 0210, // sente
  'g', 0345, 0276, 0214, // gote
  '-', 0346, 0212, 0225, // resign
   0,
  'a', 0344, 0270, 0200, // in reality these are numbers in Japanese a=1, b=2 etc.
  'b', 0344, 0272, 0214,
  'c', 0344, 0270, 0211,
  'd', 0345, 0233, 0233,
  'e', 0344, 0272, 0224,
  'f', 0345, 0205, 0255,
  'g', 0344, 0270, 0203,
  'h', 0345, 0205, 0253,
  'i', 0344, 0271, 0235,
  ' ', 0343, 0200, 0200,
   0,
  'K', 0347, 0216, 0211, // piece names
  'K', 0347, 0216, 0213,
  'G', 0351, 0207, 0221,
  'S', 0351, 0212, 0200,
  'R', 0351, 0243, 0233,
  'B', 0350, 0247, 0222,
  'N', 0346, 0241, 0202,
  'L', 0351, 0246, 0231,
  'P', 0346, 0255, 0251,
  'r', 0351, 0276, 0215,
  'b', 0351, 0246, 0254,
  'p', 0343, 0201, 0250,
  'r', 0347, 0253, 0234,
  '+', 0346, 0210, 0220,
  'G', 0, 0, 0,
   0,
  '+', 0346, 0210, 0220, // helper
  '@', 0346, 0211, 0223,
  'p', 0346, 0211, 0213, // player
  ':', 0357, 0274, 0232,
  '-', 0344, 0272, 0206,
  'f', 0344, 0270, 0212,
  's', 0345, 0257, 0204,
  'b', 0345, 0274, 0225,
  'r', 0345, 0267, 0246,
  'l', 0345, 0217, 0263,
  'v', 0347, 0233, 0264,
   0,
   // shift-JIS
  '1', 0202, 0120, 0,
  '2', 0202, 0121, 0,
  '3', 0202, 0122, 0,
  '4', 0202, 0123, 0,
  '5', 0202, 0124, 0,
  '6', 0202, 0125, 0,
  '7', 0202, 0126, 0,
  '8', 0202, 0127, 0,
  '9', 0202, 0130, 0,
  'x', 0223, 0257, 0,
  's', 0220, 0346, 0,
  'g', 0214, 0343, 0,
  '-', 0223, 0212, 0,
   0,
  'a', 0210, 0352, 0, 
  'b', 0223, 0361, 0, 
  'c', 0216, 0117, 0, 
  'd', 0216, 0154, 0, 
  'e', 0214, 0334, 0, 
  'f', 0230, 0132, 0, 
  'g', 0216, 0265, 0, 
  'h', 0224, 0252, 0, 
  'i', 0213, 0343, 0, 
  ' ', 0201, 0100, 0, 
   0,
  'K', 0213, 0312, 0, 
  'K', 0213, 0312, 0, 
  'G', 0213, 0340, 0, 
  'S', 0213, 0342, 0, 
  'R', 0224, 0362, 0, 
  'B', 0212, 0160, 0,
  'N', 0214, 0152, 0, 
  'L', 0215, 0201, 0, 
  'P', 0225, 0340, 0, 
  'r', 0227, 0264, 0, 
  'b', 0224, 0156, 0, 
  'p', 0202, 0306, 0, 
  'r', 0227, 0263, 0, 
  '+', 0220, 0254, 0, 
  'G', 0, 0, 0, 
   0,
  '+', 0220, 0254, 0, 
  '@', 0221, 0305, 0, 
//  'p', 0214, 0343, 0,
  'p', 0216, 0350, 0,
  ':', 0201, 0106, 0,
  '-', 0227, 0271, 0,
  'f', 0217, 0343, 0,
  's', 0212, 0361, 0,
  'b', 0210, 0370, 0,
  'r', 0215, 0266, 0,
  'l', 0211, 0105, 0,
  'v', 0222, 0274, 0,
   0,
     
};

int NextUnit P((char **p));

int kifu = 0;

char
GetKanji (char **p, int start)
{
    unsigned char *q = *(unsigned char **) p;
    int i;

    if((*q & 0x80) == 0) return 0; // plain ASCII, refuse to parse
    if((**p & 0xC0) == 0x80) { // this is an illegal starting code in utf-8, so assume shift-JIS
        for(i=start+JIS; kanjiTab[i]; i+=4) {
            if(q[0] == kanjiTab[i+1] && q[1] == kanjiTab[i+2]) {
                (*p) += 2; kifu = 0x80;
                return kanjiTab[i];
            }
        }
        (*p) += (kifu ? 2 : 1); // assume this is an unrecognized kanji when reading kif files
        return 0;
    }

    for(i=start; kanjiTab[i]; i+=4) {
        if(q[0] == kanjiTab[i+1] && q[1] == kanjiTab[i+2] && q[2] == kanjiTab[i+3]) {
            (*p) += 3; kifu = 0x80;
            return kanjiTab[i];
        }
    }

    if((q[0] & 0xE0) == 0xC0 && (q[1] & 0xC0) == 0x80) (*p) += 2; else // for now skip unrecognized utf-8 characters
    if((q[0] & 0xF0) == 0xE0 && (q[1] & 0xC0) == 0x80 && (q[2] & 0xC0) == 0x80) (*p) += 3; else
    if((q[0] & 0xF8) == 0xF0 && (q[1] & 0xC0) == 0x80 && (q[2] & 0xC0) == 0x80 && (q[3] & 0xC0) == 0x80) (*p) += 4;
    else if(**p & 0x80) return -1; // not valid utf-8

    return 0; // unrecognized but valid kanji (skipped), or plain ASCII
}

int
KifuMove (char **p)
{
    static char buf[MSG_SIZ];
    char *ptr = buf+3, *q, k;
    int wom = quickFlag ? quickFlag&1 : WhiteOnMove(yyboardindex);
    k = GetKanji(p, XCO);
    if(k < 0) { (*p)++; return Nothing; } // must try shift-JIS here
    if(k >= '1' && k <= '9') {
        buf[0] = k; buf[1] = GetKanji(p, YCO); // to-square coords
    } else if(k == 'x') {
        if(GetKanji(p, YCO) != ' ') (*p) -= 3; // skip spacer kanji after recapture 
    } else if((k == 's' || k == 'g') && GetKanji(p, MISC) == 'p' && GetKanji(p, MISC) == ':') { // player name
        snprintf(yytext, MSG_SIZ, "[%s \"", k == 's' ? "White" : "Black"); // construct PGN tag
        for(q=yytext+8; **p && **p != '\n' && **p != '\r' && q < yytext + MSG_SIZ; ) *q++ = *(*p)++;
        strcpy(q, "\"]\n"); parseStart = yytext; lastChar = '\n';
        return PGNTag;
    } else if(k == '-' && GetKanji(p, MISC) == '-') { // resign
        int res;
        parseStart = yytext;
        if(wom)
             res = BlackWins, strcpy(yytext, "{sente resigns} 0-1"); 
        else res = WhiteWins, strcpy(yytext, "{gote resigns} 1-0");
        return res;
    } else {
        while(**p && **p != '\n') (*p)++; // unrecognized Japanese kanji: skip to end of line
        return Nothing;
    }
    buf[3] = GetKanji(p, PIECE); // piece ID
    if(buf[3] == '+') buf[2] = '+', buf[3] = GetKanji(p, PIECE); // +N, +L, +S
    k = GetKanji(p, MISC);
    if(k == '@') { // drop move
        buf[4] = '@', buf[5] = buf[0], buf[6] = buf[1]; buf[7] = NULLCHAR;
        if(appData.debugMode) fprintf(debugFP, "kifu drop %s\n", ptr);
        return NextUnit(&ptr);
    }

    kifu = 0x80;
    do { // read disambiguation (and promotion) kanji
        switch(k) {
          case '+': kifu |= 1; break;
          case 'f': kifu |= 2; break;
          case 'b': kifu |= 4; break;
          case 's': kifu |= 8; break;
          case 'l': kifu |= 0x10; break;
          case 'r': kifu |= 0x20; break;
          case 'v': kifu |= 0x40; break;
        }
    } while(k = GetKanji(p, MISC));

    if(**p == '(' && (*p)[3] == ')') { // kif disambiguation
        buf[4] = (*p)[1]; buf[5] = (*p)[2] + 'a' - '1'; buf[6] = buf[0]; buf[7] = buf[1]; buf[8] = (kifu & 1)*'+'; buf[9] = NULLCHAR;
        (*p) += 4; ptr++; // strip off piece name if we know full from-square
        if(appData.debugMode) fprintf(debugFP, "kifu move %s\n", ptr);
        return NextUnit(&ptr);
    } else { // kif2
        char *q = buf+4;
        if(islower(buf[3])) // kludge: kanji for promoted types translate as lower case
            buf[3] += 'A' - 'a', buf[2] = '+', ptr--;        // so prefix with '+'
        if(kifu * ~1) { // disambiguation was given, and thus is probably needed
            if(buf[3] != 'B' && buf[3] != 'R') {                // stepper, so distance must be <= 1 (N or L never need vertical disambiguation!)
                if(kifu & 0x10) *q++ = buf[0] - (wom ? -1 : 1); // translate left/right/straight to PSN file disambiguators
                if(kifu & 0x20) *q++ = buf[0] + (wom ? -1 : 1);
                if(kifu & 0x40) *q++ = buf[0], kifu |= 2;       // kludge: 'straight' only needs disambiguation if forward!
                if(kifu & 2) *q++ = buf[1] + (wom ? -1 : 1);    // translate forward/backward/sideway to PSN rank disambiguators
                if(kifu & 4) *q++ = buf[1] - (wom ? -1 : 1);
                if(kifu & 8) *q++ = buf[1];
            } // for B, R, +B and +R it gets ugly, as we cannot deduce the distance, and the Disambiguate callback has to directly look at 'kifu'
        }
        *q++ = buf[0]; *q++ = buf[1]; *q++ = (kifu & 1)*'+'; *q = NULLCHAR;
        if(appData.debugMode) fprintf(debugFP, "kif2 move %s\n", ptr);
        return NextUnit(&ptr);
    }
}

int
ReadLine ()
{   // Read one line from the input file, and append to the buffer
    char c, *start = inPtr;
    if(fromString) return 0; // parsing string, so the end is a hard end
    if(!inputFile) return 0;
    while((c = fgetc(inputFile)) != EOF) {
        *inPtr++ = c;
        if(c == '\n') { *inPtr = NULLCHAR; return 1; }
        if(inPtr - inputBuf > PARSEBUFSIZE-2) inPtr--; //prevent crash on overflow
    }
    if(inPtr == start) return 0;
    *inPtr++ = '\n', *inPtr = NULLCHAR; // repair missing linefeed at EOF
    return 1;
}

int
Scan (char c, char **p)
{   // line-spanning skip to mentioned character or EOF
    do {
        while(**p) if(*(*p)++ == c) return 0;
    } while(ReadLine());
    // no closing bracket; force match for entire rest of file.
    return 1;
}

int
SkipWhite (char **p)
{   // skip spaces tabs and newlines; return 1 if anything was skipped
    char *start = *p;
    do{
        while(**p == ' ' || **p == '\t' || **p == '\n' || **p == '\r') (*p)++;
    } while(**p == NULLCHAR && ReadLine()); // continue as long as ReadLine reads something
    return *p != start;
}

static inline int
Match (char *pattern, char **ptr)
{
    char *p = pattern, *s = *ptr;
    while(*p && (*p == *s++ || s[-1] == '\r' && *p--)) p++;
    if(*p == 0) {
        *ptr = s;
        return 1;
    }
    return 0; // no match, no ptr update
}

static inline int
Word (char *pattern, char **p)
{
    if(Match(pattern, p)) return 1;
    if(*pattern >= 'a' && *pattern <= 'z' && *pattern - **p == 'a' - 'A') { // capitalized
        (*p)++;
        if(Match(pattern + 1, p)) return 1;
        (*p)--;
    }
    return 0;
}

int
Verb (char *pattern, char **p)
{
    int res = Word(pattern, p);
    if(res && !Match("s", p)) Match("ed", p); // eat conjugation suffix, if any
    return res;
}

int
Number (char **p)
{
    int val = 0;
    if(**p < '0' || **p > '9') return BADNUMBER;
    while(**p >= '0' && **p <= '9') {
        val = 10*val + *(*p)++ - '0';
    }
    return val;
}

int
RdTime (char c, char **p)
{
    char *start = ++(*p), *sec; // increment *p, as it was pointing to the opening ( or {
    if(Number(p) == BADNUMBER) return 0;
    sec = *p;
    if(Match(":", p) && Number(p) != BADNUMBER && *p - sec == 3) { // well formed
        sec = *p;
        if(Match(".", p) && Number(p) != BADNUMBER && *(*p)++ == c) return 1; // well-formed fraction
        *p = sec;
        if(*(*p)++ == c) return 1; // matching bracket without fraction
    }
    *p = start; // failure
    return 0;
}

char
PromoSuffix (char **p)
{
    char *start = *p;
    if(**p == 'e' && (Match("ep", p) || Match("e.p.", p))) { *p = start; return NULLCHAR; } // non-compliant e.p. suffix is no promoChar!
    if(**p == '+' && IS_SHOGI(gameInfo.variant)) { (*p)++; return '+'; }
    if(**p == '=' || (gameInfo.variant == VariantSChess) && **p == '/') (*p)++; // optional = (or / for Seirawan gating)
    if(**p == '(' && (*p)[2] == ')' && isalpha( (*p)[1] )) { (*p) += 3; return ToLower((*p)[-2]); }
    if(isalpha(**p) && **p != 'x') return ToLower(*(*p)++); // reserve 'x' for multi-leg captures? 
    if(*p != start) return **p == '+' ? *(*p)++ : '='; // must be the optional = (or =+)
    return NULLCHAR; // no suffix detected
}

int
NextUnit (char **p)
{       // Main parser routine
        int coord[4], n, result, piece, i;
        char type[4], promoted, separator, slash, *oldp, *commentEnd, c;
        int wom = quickFlag ? quickFlag&1 : WhiteOnMove(yyboardindex);

        // ********* try white first, because it is so common **************************
        if(**p == ' ' || **p == '\n' || **p == '\t') { parseStart = (*p)++; return Nothing; }


        if(**p == NULLCHAR) { // make sure there is something to parse
            if(fromString) return 0; // we are parsing string, so the end is really the end
            *p = inPtr = inputBuf;
            if(!ReadLine()) return 0; // EOF
        } else if(inPtr > inputBuf + PARSEBUFSIZE/2) { // buffer fills up with already parsed stuff
            char *q = *p, *r = inputBuf;
            while(*r++ = *q++);
            *p = inputBuf; inPtr = r - 1;
        }
        parseStart = oldp = *p; // remember where we begin

        // ********* attempt to recognize a SAN move in the leading non-blank text *****
        piece = separator = promoted = slash = n = 0;
        for(i=0; i<4; i++) coord[i] = -1, type[i] = NOTHING;
        if(**p & 0x80) return KifuMove(p); // non-ascii. Could be some kanj notation for Shogi or Xiangqi
        if(**p == '+') (*p)++, promoted++;
        if(**p >= 'a' && **p <= 'z' && (*p)[1]== '@') piece =*(*p)++ + 'A' - 'a'; else
        if(**p >= 'A' && **p <= 'Z') {
             static char s[] = SUFFIXES;
             char *q;
             piece = *(*p)++; // Note we could test for 2-byte non-ascii names here
             if(q = strchr(s, **p)) (*p)++, piece += 64*(q - s + 1);
             if(**p == '/') slash = *(*p)++;
        }
        while(n < 4) {
            if(**p >= 'a' && **p < 'x') coord[n] = *(*p)++ - 'a', type[n++] = ALPHABETIC;
            else if((i = Number(p)) != BADNUMBER) coord[n] = i, type[n++] = NUMERIC;
            else break;
            if(n == 2 && type[0] == type[1]) { // if two identical types, the opposite type in between must have been missing
                type[2] = type[1]; coord[2] = coord[1];
                type[1] = NOTHING; coord[1] = -1; n++;
            }
        }
        // we always get here, and might have read a +, a piece, and upto 4 potential coordinates
        if(n <= 2) { // could be from-square or disambiguator, when -:xX follow, or drop with @ directly after piece, but also to-square
             if(**p == '-' || **p == ':' || **p == 'x' || **p == 'X' || // these cannot be move suffix, so to-square must follow
                 (**p == '@' || **p == '*') && n == 0 && !promoted && piece) { // P@ must also be followed by to-square
                separator = *(*p)++;
                if(n == 1) coord[1] = coord[0]; // must be disambiguator, but we do not know which yet
                n = 2;
                while(n < 4) { // attempt to read to-square
                    if(**p >= 'a' && **p < 'x') coord[n] = *(*p)++ - 'a', type[n++] = ALPHABETIC;
                    else if((i = Number(p)) != BADNUMBER) coord[n] = i, type[n++] = NUMERIC;
                    else break;
                }
            } else if((**p == '+' || **p == '=') && n == 1 && piece && type[0] == NUMERIC) { // can be traditional Xiangqi notation
                separator = *(*p)++;
                n = 2;
                if((i = Number(p)) != BADNUMBER) coord[n] = i, type[n++] = NUMERIC;
            } else if(n == 2) { // only one square mentioned, must be to-square
                while(n < 4) { coord[n] = coord[n-2], type[n] = type[n-2], coord[n-2] = -1, type[n-2] = NOTHING; n++; }
            }
        } else if(n == 3 && type[1] != NOTHING) { // must be hyphenless disambiguator + to-square
            for(i=3; i>0; i--) coord[i] = coord[i-1], type[i] = type[i-1]; // move to-square to where it belongs
            type[1] = NOTHING; // disambiguator goes in first two positions
            n = 4;
        }
        // we always get here; move must be completely read now, with to-square coord(s) at end
        if(n == 3) { // incomplete to-square. Could be Xiangqi traditional, or stuff like fxg
            if(piece && type[1] == NOTHING && type[0] == NUMERIC && type[2] == NUMERIC &&
                (separator == '+' || separator == '=' || separator == '-')) {
                     // Xiangqi traditional

                return ImpossibleMove; // for now treat as invalid
            }
            // fxg stuff, but also things like 0-0, 0-1 and 1-0
            if(!piece && type[1] == NOTHING && type[0] == ALPHABETIC && type[2] == ALPHABETIC
                 && (coord[0] != 14 || coord[2] != 14) /* reserve oo for castling! */ ) {
                piece = 'P'; n = 4; // kludge alert: fake full to-square
            }
        } else if(n == 1 && type[0] == NUMERIC && coord[0] > 1) { while(**p == '.') (*p)++; return Nothing; } // fast exit for move numbers
        if(n == 4 && type[2] != type[3] && // we have a valid to-square (kludge: type[3] can be NOTHING on fxg type move)
                     (piece || !promoted) && // promoted indicator only valid on named piece type
                     (type[2] == ALPHABETIC || IS_SHOGI(gameInfo.variant))) { // in Shogi also allow alphabetic rank
            DisambiguateClosure cl;
            int fromX, fromY, toX, toY;

            if(slash && (!piece || type[1] == NOTHING)) goto badMove; // slash after piece only in ICS long format
            if (yyskipmoves) return (int) AmbiguousMove; /* not disambiguated */

            if(type[2] == NUMERIC) { // alpha-rank
                coord[2] = BOARD_RGHT - BOARD_LEFT - coord[2];
                coord[3] = BOARD_HEIGHT - coord[3];
                if(coord[0] >= 0) coord[0] = BOARD_RGHT - BOARD_LEFT - coord[0];
                if(coord[1] >= 0) coord[1] = BOARD_HEIGHT - coord[1];
            }
            toX = cl.ftIn = (currentMoveString[2] = coord[2] + 'a') - AAA;
            toY = cl.rtIn = (currentMoveString[3] = coord[3] + '0') - ONE;
            if(type[3] == NOTHING) cl.rtIn = -1; // for fxg type moves ask for toY disambiguation
            else if(toY >= BOARD_HEIGHT || toY < 0)   return ImpossibleMove; // vert off-board to-square
            if(toX < BOARD_LEFT || toX >= BOARD_RGHT) return ImpossibleMove;
            if(piece) {
                cl.pieceIn = CharToPiece(wom ? piece : piece + 'a' - 'A');
                if(cl.pieceIn == EmptySquare) return ImpossibleMove; // non-existent piece
                if(promoted) cl.pieceIn = (ChessSquare) (CHUPROMOTED cl.pieceIn);
            } else cl.pieceIn = EmptySquare;
            if(separator == '@' || separator == '*') { // drop move. We only get here without from-square or promoted piece
                fromY = DROP_RANK; fromX = cl.pieceIn;
                currentMoveString[0] = piece;
                currentMoveString[1] = '@';
                currentMoveString[4] = NULLCHAR;
                return LegalityTest(boards[yyboardindex], PosFlags(yyboardindex)&~F_MANDATORY_CAPTURE, fromY, fromX, toY, toX, NULLCHAR);
            }
            if(type[1] == NOTHING && type[0] != NOTHING) { // there is a disambiguator
                if(type[0] != type[2]) coord[0] = -1, type[1] = type[0], type[0] = NOTHING; // it was a rank-disambiguator
            }
            if(  type[1] != type[2] && // means fromY is of opposite type as ToX, or NOTHING
                (type[0] == NOTHING || type[0] == type[2]) ) { // well formed

                fromX = (currentMoveString[0] = coord[0] + 'a') - AAA;
                fromY = (currentMoveString[1] = coord[1] + '0') - ONE;
                currentMoveString[4] = cl.promoCharIn = PromoSuffix(p);
                currentMoveString[5] = NULLCHAR;
                if(!cl.promoCharIn && (**p == '-' || **p == 'x')) { // Lion-type multi-leg move
                    currentMoveString[5] = (killX = toX) + AAA; // what we thought was to-square is in fact kill-square
                    currentMoveString[6] = (killY = toY) + ONE; // append it as suffix behind long algebraic move
                    currentMoveString[4] = ';';
                    currentMoveString[7] = NULLCHAR;
                    // read new to-square (VERY non-robust! Assumes correct (non-alpha-rank) syntax, and messes up on errors)
                    toX = cl.ftIn = (currentMoveString[2] = *++*p) - AAA; ++*p;
                    toY = cl.rtIn = (currentMoveString[3] = Number(p) + '0') - ONE;
                }
                if(type[0] != NOTHING && type[1] != NOTHING && type[3] != NOTHING) { // fully specified.
                    ChessSquare realPiece = boards[yyboardindex][fromY][fromX];
                    // Note that Disambiguate does not work for illegal moves, but flags them as impossible
                    if(piece) { // check if correct piece indicated
                        if(PieceToChar(realPiece) == '~') realPiece = (ChessSquare) (DEMOTED realPiece);
                        if(!(appData.icsActive && PieceToChar(realPiece) == '+') && // trust ICS if it moves promoted pieces
                           piece && realPiece != cl.pieceIn) return ImpossibleMove;
                    } else if(!separator && **p == '+') { // could be a protocol move, where bare '+' suffix means shogi-style promotion
                        if(realPiece < (wom ?  WhiteCannon : BlackCannon) && PieceToChar(PROMOTED realPiece) == '+') // seems to be that
                           currentMoveString[4] = cl.promoCharIn = *(*p)++; // append promochar after all
                    }
                    result = LegalityTest(boards[yyboardindex], PosFlags(yyboardindex), fromY, fromX, toY, toX, cl.promoCharIn);
                    if (currentMoveString[4] == NULLCHAR) { // suppy missing mandatory promotion character
                      if(result == WhitePromotion  || result == BlackPromotion) {
                        switch(gameInfo.variant) {
                          case VariantCourier:
                          case VariantShatranj: currentMoveString[4] = PieceToChar(BlackFerz); break;
                          case VariantGreat:    currentMoveString[4] = PieceToChar(BlackMan); break;
                          case VariantShogi:    currentMoveString[4] = '+'; break;
                          default:              currentMoveString[4] = PieceToChar(BlackQueen);
                        }
                      } else if(result == WhiteNonPromotion  || result == BlackNonPromotion) {
                                                currentMoveString[4] = '=';
                      }
                    } else if(appData.testLegality && gameInfo.variant != VariantSChess && // strip off unnecessary and false promo characters
                       !(result == WhitePromotion  || result == BlackPromotion ||
                         result == WhiteNonPromotion || result == BlackNonPromotion)) currentMoveString[4] = NULLCHAR;
                    return result;
                } else if(cl.pieceIn == EmptySquare) cl.pieceIn = wom ? WhitePawn : BlackPawn;
                cl.ffIn = type[0] == NOTHING ? -1 : coord[0] + 'a' - AAA;
                cl.rfIn = type[1] == NOTHING ? -1 : coord[1] + '0' - ONE;

                Disambiguate(boards[yyboardindex], PosFlags(yyboardindex), &cl);

                if(cl.kind == ImpossibleMove && !piece && type[1] == NOTHING // fxg5 type
                        && toY == (wom ? 4 : 3)) { // could be improperly written e.p.
                    cl.rtIn += wom ? 1 : -1; // shift target square to e.p. square
                    Disambiguate(boards[yyboardindex], PosFlags(yyboardindex), &cl);
                    if((cl.kind != WhiteCapturesEnPassant && cl.kind != BlackCapturesEnPassant))
                        return ImpossibleMove; // nice try, but no cigar
                }

                currentMoveString[0] = cl.ff + AAA;
                currentMoveString[1] = cl.rf + ONE;
                currentMoveString[3] = cl.rt + ONE;
                if(killX < 0) // [HGM] lion: do not overwrite kill-square suffix
                currentMoveString[4] = cl.promoChar;

                if((cl.kind == WhiteCapturesEnPassant || cl.kind == BlackCapturesEnPassant) && (Match("ep", p) || Match("e.p.", p)));

                return (int) cl.kind;
            }
        }
badMove:// we failed to find algebraic move
        *p = oldp;


        // Next we do some common symbols where the first character commits us to things that cannot possibly be a move

        // ********* PGN tags ******************************************
        if(**p == '[') {
            oldp = ++(*p); kifu = 0;
            if(Match("--", p)) { // "[--" could be start of position diagram
                if(!Scan(']', p) && (*p)[-3] == '-' && (*p)[-2] == '-') return PositionDiagram;
                *p = oldp;
            }
            SkipWhite(p);
            if(isdigit(**p) || isalpha(**p)) {
                do (*p)++; while(isdigit(**p) || isalpha(**p) || **p == '+' ||
                                **p == '-' || **p == '=' || **p == '_' || **p == '#');
                SkipWhite(p);
                if(**p == '"') {
                    (*p)++;
                    while(**p != '\n' && (*(*p)++ != '"'|| (*p)[-2] == '\\')); // look for unescaped quote
                    if((*p)[-1] !='"') { *p = oldp; Scan(']', p); return Comment; } // string closing delimiter missing
                    SkipWhite(p); if(*(*p)++ == ']') return PGNTag;
                }
            }
            Scan(']', p); return Comment;
        }

        // ********* SAN Castings *************************************
        if(**p == 'O' || **p == 'o' || **p == '0' && !Match("00:", p)) { // exclude 00 in time stamps
            int castlingType = 0;
            if(Match("O-O-O", p) || Match("o-o-o", p) || Match("0-0-0", p) ||
               Match("OOO", p) || Match("ooo", p) || Match("000", p)) castlingType = 2;
            else if(Match("O-O", p) || Match("o-o", p) || Match("0-0", p) ||
                    Match("OO", p) || Match("oo", p) || Match("00", p)) castlingType = 1;
            if(castlingType) { //code from old parser, collapsed for both castling types, and streamlined a bit
                int rf, ff, rt, ft; ChessSquare king;
                char promo=NULLCHAR;

                if(gameInfo.variant == VariantSChess) promo = PromoSuffix(p);

                if (yyskipmoves) return (int) AmbiguousMove; /* not disambiguated */

                if (wom) {
                    rf = castlingRank[0];
                    rt = castlingRank[0];
                    king = WhiteKing;
                } else {
                    rf = castlingRank[3];
                    rt = castlingRank[3];
                    king = BlackKing;
                }
                ff = (BOARD_WIDTH-1)>>1; // this would be d-file
                if (boards[yyboardindex][rf][ff] == king) {
                    /* ICS wild castling */
                    ft = castlingType == 1 ? BOARD_LEFT+1 : (gameInfo.variant == VariantJanus ? BOARD_RGHT-2 : BOARD_RGHT-3);
                } else {
                    char *q;
                    ff = BOARD_WIDTH>>1; // e-file
                    ft = castlingType == 1 ? BOARD_RGHT-2 : BOARD_LEFT+2;
                    if(pieceDesc[king] && (q = strchr(pieceDesc[king], 'O'))) { // redefined to non-default King stride
                        ft = (castlingType == 1 ? ff + atoi(q+1) : ff - atoi(q+1));
                    }
                }
                if(PosFlags(0) & F_FRC_TYPE_CASTLING) {
                    if (wom) {
                        ff = initialRights[2];
                        ft = initialRights[castlingType-1];
                    } else {
                        ff = initialRights[5];
                        ft = initialRights[castlingType+2];
                    }
                    if (appData.debugMode) fprintf(debugFP, "Parser FRC (type=%d) %d %d\n", castlingType, ff, ft);
                    if(ff == NoRights || ft == NoRights) return ImpossibleMove;
                }
                sprintf(currentMoveString, "%c%c%c%c%c",ff+AAA,rf+ONE,ft+AAA,rt+ONE,promo);
                if (appData.debugMode) fprintf(debugFP, "(%d-type) castling %d %d\n", castlingType, ff, ft);

                return (int) LegalityTest(boards[yyboardindex],
                              PosFlags(yyboardindex)&~F_MANDATORY_CAPTURE, // [HGM] losers: e.p.!
                              rf, ff, rt, ft, promo);
            } else if(Match("01", p)) return Nothing; // prevent this from being mistaken for move number 1
        }


        // ********* variations (nesting) ******************************
        if(**p =='(') {
            if(RdTime(')', p)) return ElapsedTime;
            return Open;
        }
        if(**p ==')') { (*p)++; return Close; }
        if(**p == ';') { while(**p != '\n') (*p)++; return Comment; }


        // ********* Comments and result messages **********************
        *p = oldp; commentEnd = NULL; result = 0;
        if(**p == '{') {
            if(RdTime('}', p)) return ElapsedTime;
            if(lastChar == '\n' && Match("--------------\n", p)) {
                char *q;
                i = Scan ('}', p); q = *p - 16;
                if(Match("\n--------------}\n", &q)) return PositionDiagram;
            } else i = Scan('}', p);
            commentEnd = *p; if(i) return Comment; // return comment that runs to EOF immediately
        }
        if(commentEnd) SkipWhite(p);
        if(kifu && **p == '*') { // .kif comment
            char *q = yytext;
            while(**p && **p != '\n') { if(q < yytext + 10*MSG_SIZ-3) *q++ = **p; (*p)++; }
            parseStart = yytext; *yytext = '{'; strcpy(q, "}\n"); // wrap in braces
            return Comment;
        }
        if(Match("*", p)) result = GameUnfinished;
        else if(**p == '0') {
            if( Match("0-1", p) || Match("0/1", p) || Match("0:1", p) ||
                Match("0 - 1", p) || Match("0 / 1", p) || Match("0 : 1", p)) result = BlackWins;
        } else if(**p == '1') {
            if( Match("1-0", p) || Match("1/0", p) || Match("1:0", p) ||
                Match("1 - 0", p) || Match("1 / 0", p) || Match("1 : 0", p)) result = WhiteWins;
            else if(Match("1/2 - 1/2", p) || Match("1/2:1/2", p) || Match("1/2 : 1/2", p) || Match("1 / 2 - 1 / 2", p) ||
                    Match("1 / 2 : 1 / 2", p) || Match("1/2", p) || Match("1 / 2", p)) result = GameIsDrawn;
        }
        if(result) {
            if(Match(" (", p) && !Scan(')', p) || Match(" {", p) && !Scan('}', p)) { // there is a comment after the PGN result!
                if(commentEnd) { *p = commentEnd; return Comment; } // so comment before it is normal comment; return that first
            }
            return result; // this returns a possible preceeding comment as result details
        }
        if(commentEnd) { *p = commentEnd; return Comment; } // there was no PGN result following, so return as normal comment


        // ********* Move numbers (after castlings or PGN results!) ***********
        if((i = Number(p)) != BADNUMBER) { // a single number was read as part of our attempt to read a move
            char *numEnd = *p;
            if(**p == '.') (*p)++; SkipWhite(p);
            if(**p == '+' || isalpha(**p) || gameInfo.variant == VariantShogi && *p != numEnd && isdigit(**p)) {
                *p = numEnd;
                return i == 1 ? MoveNumberOne : Nothing;
            }
            *p = numEnd; return Nothing;
        }


        // ********* non-compliant game-result indicators *********************
        if(Match("+-+", p) || Word("stalemate", p)) return GameIsDrawn;
        if(Match("++", p) || Verb("resign", p) || (Word("check", p) || 1) && Word("mate", p) )
            return (wom ? BlackWins : WhiteWins);
        c = ToUpper(**p);
        if(Word("w", p) && (Match("hite", p) || 1) || Word("b", p) && (Match("lack", p) || 1) ) {
            if(**p != ' ') return Nothing;
            ++*p;
            if(Verb("disconnect", p)) return GameUnfinished;
            if(Verb("resign", p) || Verb("forfeit", p) || Word("mated", p) || Word("lost", p) || Word("loses", p))
                return (c == 'W' ? BlackWins : WhiteWins);
            if(Word("mates", p) || Word("wins", p) || Word("won", p))
                return (c != 'W' ? BlackWins : WhiteWins);
            return Nothing;
        }
        if(Word("draw", p)) {
            if(**p == 'n') (*p)++;
            if(**p != ' ') return GameIsDrawn;
            oldp = ++*p;
            if(Word("agreed", p)) return GameIsDrawn;
            if(Match("by ", p) && (Word("repetition", p) || Word("agreement", p)) ) return GameIsDrawn;
            *p = oldp;
            if(*(*p)++ == '(') {
                while(**p != '\n') if(*(*p)++ == ')') break;
                if((*p)[-1] == ')')  return GameIsDrawn;
            }
            *p = oldp - 1; return GameIsDrawn;
        }


        // ********* Numeric annotation glyph **********************************
        if(**p == '$') { (*p)++; if(Number(p) != BADNUMBER) return NAG; return Nothing; }


        // ********** by now we are getting down to the silly stuff ************
        if(Word("gnu", p) || Match("GNU", p)) {
            if(**p == ' ') (*p)++;
            if(Word("chess", p) || Match("CHESS", p)) {
                char *q;
                if((q = strstr(*p, "game")) || (q = strstr(*p, "GAME")) || (q = strstr(*p, "Game"))) {
                    (*p) = q + 4; return GNUChessGame;
                }
            }
            return Nothing;
        }
        if(lastChar == '\n' && (Match("# ", p) || Match("; ", p) || Match("% ", p))) {
            while(**p != '\n' && **p != ' ') (*p)++;
            if(**p == ' ' && (Match(" game file", p) || Match(" position file", p))) {
                while(**p != '\n') (*p)++; // skip to EOLN
                return XBoardGame;
            }
            *p = oldp; // we might need to re-match the skipped stuff
        }

        if(Match("---", p)) { while(**p == '-') (*p)++; return Nothing; } // prevent separators parsing as null move
        if(Match("@@@@", p) || Match("--", p) || Match("Z0", p) || Match("pass", p) || Match("null", p)) {
            strncpy(currentMoveString, "@@@@", 5);
            return yyboardindex & F_WHITE_ON_MOVE ? WhiteDrop : BlackDrop;
        }

        // ********* Efficient skipping of (mostly) alphabetic chatter **********
        while(isdigit(**p) || isalpha(**p) || **p == '-') (*p)++;
        if(*p != oldp) {
            if(**p == '\'') {
                while(isdigit(**p) || isalpha(**p) || **p == '-' || **p == '\'') (*p)++;
                return Nothing; // random word
            }
            if(lastChar == '\n' && Match(": ", p)) { // mail header, skip indented lines
                do {
                    while(**p != '\n') (*p)++;
                    if(!ReadLine()) return Nothing; // append next line if not EOF
                } while(Match("\n ", p) || Match("\n\t", p));
            }
            return Nothing;
        }

        // ********* Prevent 00 in unprotected time stamps to be mistaken for castling *******
        if(Match(":00", p)) return Nothing;

        // ********* Could not match to anything. Return offending character ****
        (*p)++;
        return Nothing;
}

/*
    Return offset of next pattern in the current file.
*/
int
yyoffset ()
{
    return ftell(inputFile) - (inPtr - parsePtr); // subtract what is read but not yet parsed
}

void
yynewfile (FILE *f)
{   // prepare parse buffer for reading file
    inputFile = f;
    inPtr = parsePtr = inputBuf;
    fromString = 0;
    lastChar = '\n';
    *inPtr = NULLCHAR; // make sure we will start by reading a line
}

void
yynewstr P((char *s))
{
    parsePtr = s;
    inputFile = NULL;
    fromString = 1;
}

int
yylex ()
{   // this replaces the flex-generated parser
    int result = NextUnit(&parsePtr);
    char *p = parseStart, *q = yytext;
    if(p == yytext) return result;   // kludge to allow kanji expansion
    while(p < parsePtr) *q++ = *p++; // copy the matched text to yytext[]
    *q = NULLCHAR;
    lastChar = q[-1];
    return result;
}

int
Myylex ()
{   // [HGM] wrapper for yylex, which treats nesting of parentheses
    int symbol, nestingLevel = 0, i=0;
    char *p;
    static char buf[256*MSG_SIZ];
    buf[0] = NULLCHAR;
    do { // eat away anything not at level 0
        symbol = yylex();
        if(symbol == Open) nestingLevel++;
        if(nestingLevel) { // save all parsed text between (and including) the ()
            for(p=yytext; *p && i<256*MSG_SIZ-2;) buf[i++] = *p++;
            buf[i] = NULLCHAR;
        }
        if(symbol == 0) break; // ran into EOF
        if(symbol == Close) symbol = Comment, nestingLevel--;
    } while(nestingLevel || symbol == Nothing);
    yy_text = buf[0] ? buf : (char*)yytext;
    return symbol;
}

ChessMove
yylexstr (int boardIndex, char *s, char *buf, int buflen)
{
    ChessMove ret;
    char *savPP = parsePtr;
    fromString = 1;
    yyboardindex = boardIndex;
    parsePtr = s;
    ret = (ChessMove) Myylex();
    strncpy(buf, yy_text, buflen-1);
    buf[buflen-1] = NULLCHAR;
    parsePtr = savPP;
    fromString = 0;
    return ret;
}