/*
 * FILE:    cfg.c
 * PURPOSE: handling of MTPK.CFG configuration file
 * VERSION: 1.0 (Nov. 1995)
 * AUTHOR:  Piet Tutelaers
 */

#include <ctype.h>	/* isspace(), isalpha() */
#include <stdio.h>	/* fgets(), sprintf() */
#include <stdlib.h>	/* getenv() */
#include <string.h>	/* strcmp(), strlen(), strchr(), strncpy() */
#include "basics.h"	/* fatal(), (*pfopen)() */
#include "psearch.h"	/* search_file() */

/* string space */
#define MAXPOOLLEN 1024
static char pool[MAXPOOLLEN];
static char *pfree = pool;
static int left = MAXPOOLLEN;

/* where we store variable names and there values (expressions) */
#define MAXITEMS 32
static int items = 0;
static char *var[MAXITEMS], *expr[MAXITEMS];

/* determine expression via simple linear search */
static char *value(char *name, int start) {
   int i;
   char *xres = NULL;
   for (i = items -1; i >= start; i--) {
      if (strcmp(var[i], name) == 0) return expr[i];
      if (strcmp(var[i], "xres") == 0) xres = expr[i];
   }
   if (xres && strcmp(name, "res") == 0) return xres;
   return NULL;
}

/* line buffer */
static char line[MAXSTRLEN];
static char *pline;
static int count = 0;

static char *nextname() {
   char *dest;

   dest = pfree;
   while (isspace(*pline)) pline++;
   while (isalpha(*pline)) {
      *pfree++ = *pline++;
      left--;
      if (left == 0) fatal("Out of pool space\n");
   }
   if (dest == pfree) fatal("Invalid name in line %d\n", count);
   *pfree++ = '\0'; left--;
   return dest;
}

static char *nextexpression(char *expr) {
   char *dest, name[MAXSTRLEN], *pexpr;
   int i, n;

   dest = pfree;
   while (isspace(*expr)) expr++;
   while (*expr != '\0' && *expr != '\n') {
      if (*expr == '$') { /* UNIX style expressions */
	 expr++;
	 if (*expr == '(' || *expr == '{') expr++;
	 for (i = 0; isalpha(*expr); ) name[i++] = *expr++;
	 name[i] = '\0';
	 pexpr = getenv(name);
         if (pexpr == NULL) pexpr = value(name, 0);
	 if (pexpr == NULL) { /* filled in later */
	    n = strlen(name)+3;
	    if (n > left) fatal("Out of pool space\n");
	    sprintf(pfree, "${%s}", name);
	    left-=n; pfree+=n;
	    if (*expr == ')' || *expr == '}') expr++;
	    continue;
	 }
	 else {
	    n = strlen(pexpr);
	    if (n > left) fatal("Out of pool space\n");
	    strncpy(pfree, pexpr, n); left-=n; pfree+=n;
	    if (*expr == ')' || *expr == '}') expr++;
	    continue;
	 }
      }
      if (*expr == '%') { /* MSDOS style expressions */
	 char *p = expr;
	 expr++;
	 for (i = 0; isalpha(*expr); i++) name[i] = *expr++;
	 name[i] = '\0';
	 pexpr = getenv(name);
         if (pexpr == NULL) pexpr = value(name, 0);
	 if (*expr == '%' && pexpr == NULL) { /* filled in later */
	    n = strlen(name)+2;
	    if (n > left) fatal("Out of pool space\n");
	    sprintf(pfree, "%%%s%%", name);
	    left-=n; pfree+=n;
	    expr++;
	    continue;
	 }
	 else if (pexpr == NULL && strcmp(name, "b")==0) {
	    n = 6;
	    if (n > left) fatal("Out of pool space\n");
	    sprintf(pfree, "${res}");
	    left-=n; pfree+=n;
	    continue;
	 }
	 else if (pexpr == NULL && strcmp(name, "m")==0) {
	    n = 7;
	    if (n > left) fatal("Out of pool space\n");
	    sprintf(pfree, "${mode}");
	    left-=n; pfree+=n;
	    continue;
	 }
	 else if (pexpr == NULL) expr = p;
	 else {
	    n = strlen(pexpr);
	    if (n > left) fatal("Out of pool space\n");
	    strncpy(pfree, pexpr, n); left-=n; pfree+=n;
	    expr++;
	    continue;
	 }
      }
      *pfree++ = *expr++;
      if (left == 0) fatal("Out of pool space\n");
   }
   /* get rid of spaces at the end */
   while (isspace(*(pfree-1))) { pfree--; left++; }
   if (*(pfree-1) == '\0') fatal("empty expression in line %d\n", count);
   *pfree++ = '\0'; left--;
   return dest;
}

/* Determine mtpk.cfg values for <mode> and <res>. Return zero
 * if the requested values are found otherwise non-zero.
 */
int read_cfg(char *res, char *mode) {
   char *p, *r, *m, mtpkcfg[80];
   FILE *CFG; int i;

   char *section_free;
   int section_count, section_start, section_left;

   p = MTPKCFG;
   for (i=0; i < 80 && *(p+i) != '@' && *(p+i) != '\0'; i++) {
      mtpkcfg[i] = *(p+i);
   }
   mtpkcfg[i] = '\0';

   CFG = pfopen(mtpkcfg, "r");
   if (CFG == NULL) fatal("%s: can not open\n", mtpkcfg);

   while (fgets(line, MAXSTRLEN, CFG)) {
      pline = line; count++;
      if (*pline == '#' || *pline == '\n') continue;
      if (p = strchr(pline, '#')) *p = '\n';
      if (*pline == '[') {

	 /* Check if we are finished */
	 r = value("res", 0);
	 m = value("mode", 0);
	 if (r != NULL && m != NULL) {
            if (res == NULL && mode == NULL) return 0;
            if (mode == NULL && strcmp(res, r) == 0) return 0;
	    if (res == NULL && strcmp(mode, m) == 0) return 0;
	    if (res && mode && strcmp(res, r)==0 && strcmp(mode, m)==0)
	       return 0;
	 }
	 
	 /* Not yet */
	 section_count = count;
	 section_start = items;
	 section_free = pfree;
	 section_left = left;
	 pline++;
         while (*pline != '\n' && isspace(*pline)) pline++;
         if (*pline == '\n') continue;
      }
      else if (*pline == ']') {
	 if ((r = value("res", section_start)) == NULL)
	    fatal("no definition of res between lines %d and %d\n",
		   section_count, count);
	 if ((m = value("mode", section_start)) == NULL)
	    fatal("no definition of mode between lines %d and %d\n",
		   section_count, count);

	 /* Check if we are finished */
         if (res == NULL && mode == NULL) return 0;
         if (mode == NULL && strcmp(res, r) == 0) return 0;
         if (res == NULL && strcmp(mode, m) == 0) return 0;
	 if (res && mode && strcmp(res, r)==0 && strcmp(mode, m)== 0)
	    return 0;
	 
	 items = section_start;
	 pfree = section_free;
	 left = section_left;
	 continue;
      }
      /* process variable = expression */
      var[items] = nextname();
      while (isspace(*pline)) pline++;
      if (*pline != '=') fatal("Expected '=' in line %d\n", count);
      pline++;
      if (items == MAXITEMS)
	 fatal("Table overflow (MAXITEMS = %d)\n", MAXITEMS);
      expr[items] = nextexpression(pline);
      items++;
   }

   fclose(CFG);
   return 1;  
}

/* provide a function to query names */
char *cfg_value(char *variable) {
   char *v;
   v = value(variable, 0);
   if (v == NULL) return NULL;
   if (strchr(v, '$')) { /* evaluate */
      v = nextexpression(v);
      if (strchr(v, '$')) fatal("%s = %s: can not evaluate\n", variable, v);
      return v;
   }
   else 
      return v;
}