/*
*    load configuration function,
*    Copyleft (C) 2019, Nicholas Christopoulos
*/

...

/* ndc: load configuration file */
#define RC_FILE     ".rc"

typedef struct {
    const char *key; /* the name in ~/.rc */
    void    *var;   /* pointer to the variable */
    char    type;   /* type of the variable: (i)nteger, (f)loat, (s)tring */
    } rc_keyword;

/*
 *  keyword<->variable table for ~/.rc
 */
static rc_keyword rc_keys[] = {
    { "cols",       &cols,      'i' },
    { "rows",       &rows,      'i' },
    { "alpha",      &alpha,     'f' },
    { "border",     &borderpx,  'i' },
    { "borderpx",   &borderpx,  'i' },
    { "font",       &font,      's' },
    { NULL, NULL, 0 }
    };

void
load_config(void)
{
    char *p, *key, *val, *file, *home;
    char buf[LINE_MAX];
    FILE *fp;
    int  i, status = 0;

    if ( (home = (char *) getenv("HOME")) != NULL ) {
        if ( (file = (char *) malloc(strlen(home) + strlen(RC_FILE) + 2)) != NULL ) {
            sprintf(file, "%s/%s", home, RC_FILE);
            if ( (fp = fopen(file, "rt")) != NULL ) {
                while ( fgets(buf, LINE_MAX, fp) ) {
                    p = buf;
    
                    while ( *p == ' ' || *p == '\t' ) p ++;                     /* skip spaces */
                    if ( *p == '#' || *p == '\n' ) continue;                    /* comments or empty line */
                    if ( *p == '?' ) { status = system( ++ p ); continue; }     /* 'if' command, nested-ifs can be add by using push/pop status */
                    if ( *p == ':' ) { status = ( status )? 0 : 1; continue; }  /* 'else' command */
                    if ( *p == '-' ) { status = 0; continue;  }                 /* 'end-if' command */
                    if ( status != 0 ) continue;                                /* do 'if-else' check */
    
                    /* mark keyword */
                    key = p;
                    while ( *p >= 'a' && *p <= 'z'  )   p ++;
                    while ( *p == ' ' || *p == '\t' )   *p ++ = '\0';
                    if ( *p == '=' )                    *p ++ = '\0';
    
                    /* mark value */
                    val = p;
                    while ( *p && *p != '\n' ) p ++;
                    *p = '\0'; /* actually removes the '\n' on the end of buffer */
                    
                    /* apply the values */
                    for ( i = 0; rc_keys[i].key; i ++ ) {
                        if ( strcmp(key, rc_keys[i].key) == 0 ) {
                            switch ( rc_keys[i].type ) {
                            case 'i': *((int   *) rc_keys[i].var) = atoi(val); break;
                            case 'f': *((float *) rc_keys[i].var) = atof(val); break;
                            case 's': *((char **) rc_keys[i].var) = strdup(val); break;
                                }
                            break;
                            }
                        }
                    }
                fclose(fp);
                }
            free(file);
            }
        }
}

...

int
main(int argc, char *argv[])
{
    ...
    /* ndc: add ~/.rc, configuration file support */
    load_config();
    ...
}