#include <stdlib.h>             /* for exit(), getenv() */
#include <iostream>
#include <iomanip>
#include <string>

#include <sys/types.h>          /* for stat() */
#include <sys/stat.h>           /* for stat() */
#include <unistd.h>             /* for stat() */
#include <stdio.h>              /* for perror */
#include <errno.h>              /* for ENOENT */
#include <fstream>              /* for ofstream() */
#include <fcntl.h>              /* for creat() */
#include <sys/time.h>           /* for gettimeofday() */
#include <sstream>

// requires apt-get install libboost-filesystem-dev:
#include <boost/filesystem.hpp>

using namespace std;

const int minute(60);
const int hour(60*minute);
const int day(24*hour);

const int minimum_age(5*minute);
const int sa_good = 0;
const int bug_bait_grey = 1;
// qmail_queue and spamc have similar interpretations here:
const int sa_syserr = 71;

pid_t mypid;
string progname;

void dump(const string var){
  char* str = getenv(var.c_str());
  cerr << progname
    << "[" << mypid << "] "
    << var;
  if (str) cerr << " is set to '" << str << "'" << endl;
  else  cerr << " is not set." << endl;
}


   //       int stat(const char *path, struct stat *buf);
   //       int fstat(int fd, struct stat *buf);
   //       int lstat(const char *path, struct stat *buf);


class whatsit{
public:
  string dirname;
  string progname;
  pid_t mypid;
  timeval now;
  string ipbase;
  string ipname;
  string hostname;
  int mod_age;
  int ac_age;

  whatsit(const string name, const string _dirname)
  : dirname(_dirname), progname(name), mypid(getpid()), mod_age(0), ac_age(0)
  {
    gettimeofday(&now, NULL);
  }
  int doit();
// access comes after modification:
  void update(const string msg, const timeval new_mod, const timeval new_ac);
};

string time_out(const int ttt){
  int sec(ttt % 60);
  int min((ttt / 60) % 60);
  int hr(ttt / 3600);
  stringstream foo;
  foo << hr
    << ":" << setw(2) << setfill('0') << min
    << ":" << setw(2) << setfill('0') << sec;
  return foo.str();
}

void scan(const string p){
  timeval now;
  gettimeofday(&now, NULL);
  using namespace boost::filesystem;

  if (is_directory(p))  {
    for (directory_iterator itr(p); itr!=directory_iterator(); ++itr) {
      string basename = itr->path().filename();
      cout << setw(20) << basename << ' '; // display filename only
      if (is_regular_file(itr->status())) {
//        cout << " [" << file_size(itr->path()) << ']';
        struct stat mystat;
        string fn = p + "/" + basename;
        int rslt = stat(fn.c_str(), &mystat);
        if (rslt != 0){
            cerr << progname << ": stat failed for '"
              << fn << "' : ";
            perror(0);
        }
        int mod_age = now.tv_sec - mystat.st_mtime;
        int ac_age = now.tv_sec - mystat.st_atime;
        cout << setw(10) << time_out(mod_age)
                << " " << setw(10) << time_out(ac_age);
        if (mod_age < minimum_age) {
          cout << " young";
        } else if (mod_age == ac_age) {
          cout << " unused";
        }
      }
      cout << '\n';
    }
  }
  else {
    // starting point is not a directory:
    cout << (exists(p) ? "Found: " : "Not found: ") << p << '\n';
  }
}

void whatsit::update(const string msg, const timeval new_mod, const timeval new_ac){
  cerr << progname << ": "
       << msg << ": " << ipbase;
  if (hostname.length()) cerr <<  " " << hostname;
  cerr << "  mod_age: " << time_out(mod_age)
          << "  ac_age: " << time_out(ac_age)
          << endl;
  timeval upd[2] = {
// beware:  access illogically comes *before* modification here:
    new_ac,
    new_mod
  };
  utimes(ipname.c_str(), upd);
}

int main(int _argc, char** _argv){
  int argc(_argc);
  char** argv(_argv);
  const string dirname("/var/qmail/greylist");
  whatsit foo(argv[0], dirname); argc--; argv++;
  while (argc > 0) {
    string arg = argv[0]; argc--; argv++;
    if (arg == "-scan") {
      scan(dirname);
      return 0;
    }
    else {
      cerr << "Unrecognized arg, ignored: " << arg << endl;
    }
  }

  return foo.doit();
}

int whatsit::doit(){
  char* ipvar = getenv("TCPREMOTEIP");
  if (!ipvar) {
    cerr << progname << ": TCPREMOTEIP not set???" << endl;
    exit(sa_syserr);
  }
  ipbase = ipvar;
  char* hostvar = getenv("TCPREMOTEHOST");
  if (hostvar) hostname = hostvar;

// see if our directory exists:
  struct stat dirstat;
  int rslt = stat(dirname.c_str(), &dirstat);
  if (rslt != 0){
    if (errno != ENOENT) {
      cerr << progname << ": stat failed for '"
        << dirname << "' : ";
      perror(0);
    }
    rslt = mkdir(dirname.c_str(), 0755);
    if (rslt != 0) {
      cerr << progname
        << "uid " << getuid()
        << ": mkdir failed for '"
        << dirname << "' : ";
      perror(0);
      exit(sa_syserr);
    }
  }

  ipname = dirname + "/" + ipbase;
  struct stat ipstat;
  rslt = stat(ipname.c_str(), &ipstat);
  if (rslt != 0){
    if (errno != ENOENT) {
      cerr << progname << ": stat failed for '"
        << ipname << "' : ";
      perror(0);
    }
    ofstream foo;
    int fd = creat(ipname.c_str(), 0644);
    if (fd < 0){
      cerr << progname << ": create failed for '"
        << ipname << "' : ";
      perror(0);
    }
    close(fd);
    update("new customer", now, now);
    return(bug_bait_grey);
  }
// here if stat succeeded
  mod_age = now.tv_sec - ipstat.st_mtime;
  ac_age = now.tv_sec - ipstat.st_atime;
  timeval mod_orig = {ipstat.st_mtime, 0};
  if (mod_age < minimum_age) {
    update("early bird", mod_orig, now);
    return(bug_bait_grey);
  }
  if (ac_age < 32*day) {
    update("returning customer", mod_orig, now);
    return 0;
  }

// here if it is too old:
  update("too old, starting over", now, now);
  return(bug_bait_grey);
}