#include	<stdio.h>
#include	<dirent.h>
#include	<sys/stat.h>
#include	<limits.h>
#include	<time.h>
#include	<string.h>
#include	<ctype.h>

int digits(char *name){
	int r=0;
	while(isdigit(*name)){
		r++;
		name++;
	}
	return r;
}


void procFile(char *root, char *oldname, time_t mtime){
	char st[PATH_MAX], *cp, newname[PATH_MAX];
	int c;
	struct tm *t;
	cp=strrchr(oldname,'.');
	if(!cp) return;
	cp++;
	strcpy(st,cp);
	cp=st;
	while(*cp){
		(*cp)=tolower(*cp);
		cp++;
	}
	//printf("Endung=%s\n",st);
	if(strcmp(st,"pdf")) return;
	c=digits(oldname);
	//printf("%d Ziffern\n",c);
	if(c==8) return;
	t=localtime(&mtime);
	sprintf(st,"%s/%s",root,oldname);
	sprintf(newname,"%s/%04d%02d%02d_%s",root,t->tm_year+1900, t->tm_mon+1, t->tm_mday,oldname);
	printf("%s -> %s\n",st,newname);
	rename(st,newname);
}


void procDir(char *root){
	DIR *di;
	struct dirent *d;
	struct stat sb;
	char st[PATH_MAX];
	//printf("verarbeite Verzeichnis %s\n",root);
	di=opendir(root);
	if(!di) return;
	while(d=readdir(di)){
		if(d->d_name[0]!='.'){
			sprintf(st,"%s/%s",root,d->d_name);
			stat(st,&sb);
			if((sb.st_mode & S_IFMT)==S_IFDIR){
				//printf("Verzeichnis %s\n",st);
				procDir(st);
			}
			if((sb.st_mode & S_IFMT)==S_IFREG){
				//printf("Datei %s\n",st);
				procFile(root, d->d_name,sb.st_mtim.tv_sec);
			}
		}
	}
	closedir(di);
}

int main(int argc, char **argv){
	if(argc<2) return -1;
	procDir(argv[1]);
	printf("fertig.\n");
	return 0;
}