/*
 * This file is part of firk's window manager for x11 (fwm)
 * Copyright (C) 2016-2021 firk <firk@cantconnect.ru>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation.
 *
 * This program 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, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <errno.h>
#include "main.h"
#include "config.h"
#include "cfgparse.h"

#define BSZ 16384
static char buf[BSZ];
static size_t p;

static int append_str(char const * st) {
  size_t l;
  l = strlen(st);
  if(l>=BSZ-p) { logprint("(cfgparse) resulting string too long"); return -1; }
  bcopy(st, buf+p, l);
  p += l;
  buf[p] = 0;
  return 0;
}

static int append_char(char c) {
  if(1>=BSZ-p) { logprint("(cfgparse) resulting string too long"); return -1; }
  buf[p++] = c;
  buf[p] = 0;
  return 0;
}

extern char const * parse_str(char const * src, int dir) {
  char const * e;
  char c;
  size_t j;
  char en[64];
  p = 0;
  if(dir && *src=='~') {
    if(src[1] && src[1]!='/') { logprint("(cfgparse) unsupported '~' usage"); return NULL; }
    if((e = getenv("HOME")) && append_str(e)<0 || append_char('/')<0) return NULL;
    if(!src[1]) return buf;
    src+=2;
  }
  while(c=*src) {
    if(c=='\\') {
      c = *(++src);
      if(!c) { logprint("(cfgparse) got '\\' at the end"); return NULL; }
      if(append_char(c)<0) return NULL;
      src++; continue;
    }
    if(c!='$') {
      if(append_char(c)<0) return NULL;
      src++; continue;
    }
    if(src[1]!='{') {
      for(j=0; ; j++) {
        if(j>=64) { logprint("(cfgparse) '$name' - name too long"); return NULL; }
        c = src[1+j];
        if(c>='A' && c<='Z' || c>='a' && c<='z' || c>='0' && c<='9' || c=='_') en[j] = c;
        else { en[j] = 0; break; }
      }
      src += j+1;
      if((e = getenv(en)) && append_str(e)<0) return NULL;
    } else if(src[2]!='!') {
      for(j=0; ; j++) {
        if(j>=64 || !(c=src[2+j])) { logprint("(cfgparse) '${name}' - name too long and/or missing '}'"); return NULL; }
        if(c=='}') { en[j] = 0; break; }
        en[j] = c;
      }
      src += j+3;
      if((e = getenv(en)) && append_str(e)<0) return NULL;
    } else {
      for(j=0; ; j++) {
        if(j>=64 || !(c=src[3+j])) { logprint("(cfgparse) '${name}' - name too long and/or missing '}'"); return NULL; }
        if(c=='}') { en[j] = 0; break; }
        en[j] = c;
      }
      src += j+4;
      if(!(e = getenv(en))) { logprint("(cfgparse) '${!name}' - missing env var"); return NULL; }
      if(append_str(e)<0) return NULL;
    }
  }
  return buf;
}