#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dirent.h>
#include <semaphore.h>
#include <sys/stat.h>
#include <unistd.h>

sem_t * out_sem;

struct maxfile{
  char * name;
  size_t size;
};

int getsize(char *name)
{
  struct stat buf;
  stat(name,&buf);
  return buf.st_size;
}

void processdir(char *name)
{
  pid_t pid;
  DIR *dir;
  struct dirent *cur_entry;
  char *path;
  char *filename;
  int total;
  pid = getpid();
  sem_wait(out_sem);
  printf("started %d for %s\n",pid,name);
  sem_post(out_sem);
  total = 0;
  dir=opendir(name);
  chdir(name);
  path = getwd(NULL);
  while(cur_entry = readdir(dir)){
    total++;
    sem_wait(out_sem);
    printf("pid: %7d\t | %35s\t | %35s\t | %10d bytes   | total: %d\n",
     	   pid, path, cur_entry->d_name, getsize(cur_entry->d_name), total);
    sem_post(out_sem);
  }
}

int main(int argc, char *argv[])
{
  struct dirent * cur_entry;
  struct maxfile max;
  char *comp_name; // compound name
  char *ent_name;  // entry name
  DIR *dir_desc;
  DIR *dir;
  int outfile;
  long int sumsize;
  int filenum;
  int procnum;
  int N;
  pid_t p;
  int index;

  // check
  if(argc != 3){
    printf("usage: ./max <dir> <outfile>");
    exit(1);
  }
  printf("dir: %s\nfile: %s\n",argv[1],argv[2]);

  // initialization

  out_sem = sem_open("max_sem", O_CREAT);
  sem_post(out_sem);
  procnum = 0;
  sumsize = 0;
  comp_name = (char*)calloc(1024,sizeof(char));
  strcpy(comp_name,argv[1]);
  comp_name[strlen(comp_name)+1] = 0;
  comp_name[strlen(comp_name)] = '/';
  ent_name = comp_name + strlen(comp_name);
  dir = opendir(argv[1]);
  outfile = open(argv[2],O_WRONLY);
  if(!dir){
    printf("\"%s\" is not a directory\n",argv[1]);
    exit(2);
  }
  if(!outfile){
    printf("Can't open file \"%s\" for writing. Exiting.\n",argv[1]);
    exit(3);
  }
  chdir(argv[1]);
  printf("N = ");
  scanf("%d",&N);
  N--; // 4 process maximum means 3 child + 1 parent. Now N will be max child.

  // main program loop
  while(cur_entry = readdir(dir)){
    if(strcmp(cur_entry->d_name,"..") && strcmp(cur_entry->d_name,".")){
      strcpy(ent_name,cur_entry->d_name);
      if(dir_desc = opendir(comp_name)){ // this is a directory
	sem_wait(out_sem);
	printf("DIR: %s\n", comp_name);
	sem_post(out_sem);
	closedir(dir_desc);
	if(procnum<N){
	  procnum++;
	}else{
	  wait3(0,0,0); // wait any child process to exit
	}
	p = fork();
	if(!p){
	  processdir(comp_name);
	  exit(0);
	}
      }else{ // this is a file
	sem_wait(out_sem);
	printf("FILE: %s\n", comp_name);
	sem_post(out_sem);
	filenum++;
	sumsize += getsize(comp_name);
	if(getsize(comp_name) > max.size){
	  max.size = getsize(comp_name);
	  max.name = comp_name;
	}
      }
    }
  }
  while(procnum--){
    wait3(0,0,0);
  }
  printf("Catalog: %s\nTotal files: %d\nSum file size: %ld bytes\nMax file name: %s",
	 argv[1],filenum,sumsize,max.name);

  return 0;
}