#include <iostream>
#include <fcntl.h>
#include <sys/types.h>
#include <dirent.h>
#include <stdio.h>
#include <sys/file.h>

int try_lock(const char* path,const char* name)
{
    struct flock fl;
    fl.l_type=F_RDLCK;
    fl.l_whence=SEEK_SET;
    fl.l_start=0;
    fl.l_len=1;
    std::string p(path);
    p+=name;
    int fd=open(p.c_str(),O_RDONLY);
    if(fd<0) {
	std::cerr<<"Error opening file: "<<p<<": "<<strerror(errno)<<std::endl;
	return -1;
    }
    //if(fcntl(fd,F_SETLK,&fl)<0){
    if(flock(fd,LOCK_EX|LOCK_NB)<0){
	std::cerr<<"Error locking file: "<<p<<": "<<strerror(errno)<<std::endl;
	close(fd);
	return -1;
    }
    return fd;
}
void unlock(int fd)
{
    struct flock fl;
    fl.l_type=F_UNLCK;
    fl.l_whence=SEEK_SET;
    fl.l_start=0;
    fl.l_len=1;
    //fcntl(fd,F_SETLK,&fl);
    flock(fd,LOCK_UN);
    close(fd);
}

int main(int arg, char** argv)
{
    const char *path=argv[1];
    char name[20];
    while(true)
    {
	std::cout<<"Openning dir "<<path<<std::endl;
	DIR* d=opendir(path);
	if(!d)
	    std::cout<<"Error openning "<<path<<": "<<strerror(errno)<<std::endl;
	else
	    std::cout<<"Open dir "<<path<<"\n";
	struct dirent *de;
	while(true){
	    de=readdir(d);
	    if(!de){
		//std::cout<<"Error reading "<<path<<": "<<strerror(errno)<<std::endl;
		break;
	    } else {
		std::cout<<"Got dentry: "<<de->d_name<<std::endl;
	    }
	    if(de->d_name[0]=='.')
		continue;
	    strcpy(name,de->d_name);
	    int fd=try_lock(path,name);
	    if(fd>=0){
		std::cout<<"Locked "<<path<<name<<std::endl;
		if(strlen(de->d_name)>=sizeof(name)-1)
		    strcpy(name,"1");
		else
		    strncat(name,"1",sizeof(name)-1);
		if(rename(de->d_name,name)<0)
		    std::cout<<"Error renaming: "<<strerror(errno)<<std::endl;
		unlock(fd);
	    } else {
		std::cout<<"Couldn't lock "<<path<<name<<std::endl;
	    }
	}
	closedir(d);
    }
    return 0;
}