#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "lex.yy.c"

typedef struct {
   char *name;
   char *value;
} stpair;
stpair ST[4096];
int nstentry = 0;

int STindex ( char *name )
{
   int i;

   for (i=0; i<nstentry; ++i) {
      if (!strcmp(name,ST[i].name)) return i;
   }
   return -1;
}

char *STload ( char *name )
{
   int i;

   i = STindex(name);
   if (i < 0) return strdup("");
   return strdup(ST[i].value);
}

void STstore ( char *name, char *value )
{
   int i;

   i = STindex(name);
   if (i < 0) {
      i = nstentry;
      ++nstentry;
      ST[i].name = strdup(name);
   } else {
      free(ST[i].value);
   }
   ST[i].value = strdup(value);
}

int token;

void LINE ( ) ;
char *EXPR ( ) ;
char *REST ( ) ;
char *ARG ( ) ;
char *XPNT ( ) ;
char *BASE ( ) ;

void llerror ( char *msg )
{
   fprintf(stderr, "*** Error at line %d: %s\n", lineno, msg);
   exit(1);
}

void LINE ( )
{
   char *lval, *rval;

   if (token != ID) llerror("ID expected");

   /* LINE -> ID = EXPR */
   lval = strdup(yytext);

   token = yylex();
   if (token != ASG) llerror("= expected");

   token = yylex();
   rval = EXPR();
   printf("+++ Storing %s = %s\n", lval, rval);
   STstore(lval,rval);
}

char *EXPR ( )
{
   char *arg, *rest;
   int l;

   if ((token != STR) && (token != REF) && (token != LPN)) llerror("String/Reference/( expected");

   /* EXPR -> ARG REST */
   arg = ARG();
   rest = REST();
   if (rest) {
      l = strlen(arg);
      arg = (char *)realloc(arg, (l + strlen(rest) + 1) * sizeof(char));
      strcpy(arg+l,rest);
      free(rest);
   }
   return arg;
}

char *REST ( )
{
   if ( (token == RPN) || (token == EOL) ) {
      /* REST -> EMPTY */
      return NULL;
   }
   if (token == DOT) {
      /* REST -> . EXPR */
      token = yylex();
      return EXPR();
   }
   llerror("End or continuation of expression expected");
}

char *ARG ( )
{
   int repcnt, i, l;
   char *arg, *base, *xpnt, *p;

   if ((token != STR) && (token != REF) && (token != LPN)) llerror("String/Reference/( expected");

   /* ARG -> BASE XPNT */
   base = BASE();
   xpnt = XPNT();

   repcnt = (xpnt == NULL) ? 1 : atoi(xpnt);
   if (xpnt) free(xpnt);
   if (repcnt == 0) {
      base = (char *)realloc(base, sizeof(char));
      base[0] = '\0';
      return base;
   }
   if (repcnt == 1) return base;
   l = strlen(base);
   arg = (char *)malloc((repcnt * l + 1) * sizeof(char));
   p = arg;
   for (i=0; i<repcnt; ++i) {
      strcpy(p,base);
      p += l;
   }
   free(base);
   return arg;
}

char *XPNT ( )
{
   char *xpnt;
   if ((token == RPN) || (token == DOT) || (token == EOL)) {
      /* XPNT -> EMPTY */
      return NULL;
   }

   if (token == CRT) {
      /* XPNT -> ^ NUM */
      token = yylex();
      if (token != NUM) llerror("Number expected as exponent");
      xpnt = strdup(yytext);
      token = yylex();
      return xpnt;
   }

   llerror("Exponent expected");
}

char *BASE ( )
{
   char *base;

   if (token == STR) {  /* BASE -> STR */
      base = strdup(yytext);
      token = yylex();
      return base;
   }
   if (token == REF) {  /* BASE -> $ID */
      base = STload(yytext + 1);
      token = yylex();
      return base;
   }
   if (token == LPN) {  /* BASE -> ( EXPR ) */
      token = yylex();
      base = EXPR();
      if (token != RPN) llerror(") expected");
      token = yylex();
      return base;
   }

   llerror("Valid base expected");
}

int main ( int argc, char *argv[] )
{
   if (argc > 1) yyin = (FILE *)fopen(argv[1], "r");
   while (1) {
      token = yylex();
      if (token == 0) break;
      if (token == EOL) continue;
      LINE();
      if (token != EOL) {
         fprintf(stderr, "*** Parse error: New line expected\n");
         exit(1);
      }
   }
   exit(0);
}