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

#define MAX_SYMB 1000
typedef struct {
   char name[64];
   char *value;
} stentry;
typedef stentry symboltable[MAX_SYMB];

void rmws ( char *line )
{
   int i, j;

   i = j = 0;
   do {
      if ((line[i] != ' ') && (line[i] != '\t') && (line[i] != '\n')) {
         line[j] = line[i]; ++j;
      }
      ++i;
   } while (line[j]);
}

int validname ( char *str )
{
   if ( ((*str >= 'a') && (*str <= 'z')) ||
        ((*str >= 'A') && (*str <= 'Z')) ||
        (*str == '_') )
      ++str;
   else
      return 0;
   while (*str) {
      if ( ((*str >= 'a') && (*str <= 'z')) ||
           ((*str >= 'A') && (*str <= 'Z')) ||
           ((*str >= '0') && (*str <= '9')) ||
           (*str == '_') )
         ++str;
      else
         return 0;
   }
   return 1;
}

int STlookup ( char *name, symboltable ST, int nsymb )
{
   int i;

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

char *evalarg ( char *nextarg, symboltable ST, int nsymb, int *repcnt, int narg )
{
   char *p, *str;
   int i;

   p = strchr(nextarg,'^');
   if (p) *p = '\0';
   repcnt[narg] = (p) ? atoi(p+1) : 1;
   if (*nextarg == '$') {
      i = STlookup(nextarg+1,ST,nsymb);
      if (i < 0) {
         fprintf(stderr, "*** Undefined variable \"%s\"\n", nextarg+1);
         str = NULL;
      } else {
         str = ST[i].value;
      }
   } else {
      str = nextarg;
   }
   return str;
}

int parse ( char *line, symboltable ST, int nsymb )
{
   char *p, *lval, *rval, *nextarg;
   int narg, done, i, j, len, repcnt[256];
   char *arg[256], *output;

   if (!strcmp(line,"exit")) exit(0);
   p = strchr(line,'=');
   if (p == NULL) {
      fprintf(stderr, "*** No target string. Line not processed.\n");
      return nsymb;
   }
   *p = '\0';
   lval = line;
   rval = p + 1;
   if (!validname(lval)) {
      fprintf(stderr, "*** Invalid lvalue \"%s\"\n", lval);
      return nsymb;
   }
   narg = 0; done = 0;
   while (!done) {
      nextarg = rval;
      p = strchr(rval,'.');
      if (p != NULL) {
         *p = '\0';
         rval = p + 1;
      } else{
         done = 1;
      }
      arg[narg] = evalarg(nextarg,ST,nsymb,repcnt,narg);
      ++narg;
   }
   len = 0;
   for (i=0; i<narg; ++i) {
      if (arg[i]) len += repcnt[i] * strlen(arg[i]);
   }
   p = output = (char *)malloc((len + 1) * sizeof(char));
   for (i=0; i<narg; ++i) {
      if (arg[i]) {
         for (j=0; j<repcnt[i]; ++j) p += sprintf(p,"%s",arg[i]);
      }
   }
   i = STlookup(lval,ST,nsymb);
   if (i < 0) {
      strcpy(ST[nsymb].name,lval);
      ST[nsymb].value = (char *)malloc((len + 1) * sizeof(char));
      strcpy(ST[nsymb].value,output);
      ++nsymb;
   } else {
      free(ST[i].value);
      ST[i].value = (char *)malloc((len + 1) * sizeof(char));
      strcpy(ST[i].value,output);
   }
   printf("%s is set to \"%s\"\n", lval, output);
   return nsymb;
}

int procline ( char *line, symboltable ST, int nsymb )
{
   rmws(line);
   nsymb = parse(line,ST,nsymb);
   return nsymb;
}

int main ( )
{
   symboltable ST;
   int nsymb = 0;
   char line[8192];

   while (1) {
      printf("line> ");
      fgets(line, 8192, stdin);
      line[strlen(line) - 1] = '\0';
      nsymb = procline(line,ST,nsymb);
   }

   exit(0);
}