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

#include <sys/types.h>          /* for stat(), getaddrinfo() */
#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>              /* for stringstream */
#include <signal.h>             /* for kill(), SIGUSR1 */

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

#include <sys/socket.h>         /* for getaddrinfo() */
#include <netdb.h>              /* for getaddrinfo() */
#include <string.h>             /* for memset() */
#include <arpa/inet.h>          /* for inet_ntop() */

using namespace std;

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

const int minimum_age(15*minute);
const int maximum_age(32*day);
const int probation(4*hour);

#include "qq_exit_codes.h"

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;
}

void exeunt(const int sts){
  if (sts == ex_good) exit(sts);

#ifndef PENALIZE_SPAMMERS
  if (sts == ex_penaltybox) exit(sts);
#endif

#ifndef KILL_GROUP
  exit(sts);
#endif

  const char* foo = getenv("HI_Q_GROUP");
  if (!foo) exit(sts);

// No point in signalling ourself:
  sighandler_t rslt = signal(SIGUSR1, SIG_IGN);
  if (rslt == SIG_ERR) {
    cerr << "error setting signal" << endl;
  }
  int k = kill(-atoi(foo), SIGUSR1);
  if (k) {
    cerr << "kill failed on group " << atoi(foo) << " ... ";
    perror(0);
  }
  exit(sts);
}

#include "utils.h"

class whatsit{
public:
  string dirname;
  string progname;
  pid_t mypid;
  timeval now;
  char* ipvar;
  char* hostvar;
  string ipbase;
  string ipname;
  string hostname;
  int mod_age;
  int ac_age;
  string suffix;
  string progid;
  int verbosity;

  whatsit(const string name, const string _dirname)
  : dirname(_dirname), progname(name), mypid(getpid()),
    mod_age(0), ac_age(0),
    verbosity(0)
  {
    gettimeofday(&now, NULL);
  }
  int doit(const int penalty, const int stain);
// access comes after modification:
  void update(const string msg, const timeval new_mod,
        const timeval new_ac, const int penalty, const int stain);
  int setup();
  int check_dns();
  int check_dns_sub(string &addr, string &host, vector<string> &checked);
};

int whatsit::setup(){
  stringstream foo;
  foo << basename(progname) << suffix
    << "[" << mypid << "]";
  progid = foo.str();

  ipvar = getenv("TCPREMOTEIP");
  if (ipvar) ipbase = ipvar;
  hostvar = getenv("TCPREMOTEHOST");
  if (hostvar) hostname = hostvar;
  return 0;
}

void scan(const string progid, const string p, const int copies=1){
  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().string();
      for (int ii = 0; ii < copies; ii++)
        cout << setw(20) << left << 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 << progid << ": 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 (0) {

        } else if (mod_age < 0) {
          cout << " penalty";
        } else if (mod_age < ac_age) {
          cout << " parole";
        } else if (mod_age - ac_age < minimum_age    // early bird, or completely unused
          && mod_age > probation) {           // did not diligently resubmit
          cout << " disprobation";
          if (mod_age != ac_age) cout << "!";
        } else if (mod_age < minimum_age) {
          cout << " young";
          if (mod_age != ac_age) cout << "!";
        } else if (mod_age == ac_age) {
          cout << " unused";
        } else if (mod_age > maximum_age) {
          cout << " expired";
        } else {
          cout << " OK";
        }
      }
      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, const int penalty, const int stain){
  if (verbosity){
    if (penalty || stain || verbosity>1) cerr << progid << ": ";
    if (penalty) cerr << " penalty " << penalty;
    if (stain) cerr << " stain " << stain;
    if (verbosity > 1) {
      if (penalty || stain) cerr << "+";         // separation, punctuation
      cerr << msg << ": " << ipbase;
      if (hostname.length()) cerr <<  " " << hostname;
      cerr << "  mod_age: " << time_out(mod_age)
              << "  ac_age: " << time_out(ac_age);
    }
    cerr << endl;
  }
  timeval pen_mod(new_mod);
  timeval stain_ac(new_ac);
  if (penalty) {
    pen_mod = now;
    pen_mod.tv_sec += penalty;
  }
  if (stain) {
    stain_ac = now;
    stain_ac.tv_sec -= stain;
  }
  timeval upd[2] = {
// beware:  access illogically comes *before* modification here:
    stain_ac,
    pen_mod
  };
  if (utimes(ipname.c_str(), upd))
    cerr << "oops" << endl;
}


int main(int _argc, char** _argv){
  mypid = getpid();
  int argc(_argc);
  char** argv(_argv);
  const string dirname("/var/qmail/greylist");
  whatsit foo(argv[0], dirname); argc--; argv++;
  int scanmode(0);
  int copies(1);
  int penalty(0);
  int stain(0);
  int check(0);
  while (argc > 0) {
    string arg = argv[0]; argc--; argv++;
    if (prefix(arg, "-scan")) {
      scanmode++;
    } else if (prefix(arg, "-copy"))  {
      copies++;
    } else if (prefix(arg, "-verbose"))  {
      foo.verbosity++;
    } else if (prefix(arg, "-check"))  {
      check++;
    } else if (prefix(arg, "-penalize")
        || prefix(arg, "-penalty"))  {
      if (!argc){
        cerr << "Option '" << arg << "' requires an argument" << endl;
        exeunt(ex_syserr);
      }
      penalty = atoi(*argv++);  argc--;
    } else if (prefix(arg, "-stain"))  {
      if (!argc){
        cerr << "Option '" << arg << "' requires an argument" << endl;
        exeunt(ex_syserr);
      }
      stain = atoi(*argv++);  argc--;
    } else if (prefix(arg, "-suffix")) {
      if (!argc){
        cerr << "Option '" << arg << "' requires an argument" << endl;
        exeunt(ex_syserr);
      }
      foo.suffix += *argv++;  argc--;
    } else {
      cerr << "Unrecognized arg: " << arg << endl;
      exeunt(ex_syserr);
    }
  }
  if (foo.setup()) return ex_syserr;

  if (scanmode) {
    scan(foo.progid, dirname, copies);
    return 0;
  }

  int sts = foo.doit(penalty, stain);
  if (sts == ex_syserr) return sts;
  if (!check) return ex_good;

// check mode ... perform some extra checks.
// Probably a better design would be to
//  (a) make more thorough DNS checks, and
//  (b) move all the DNS checking to a separate module

  int dns = foo.check_dns();
  if (dns == ex_syserr || dns == ex_spam) return dns;
  exeunt(sts);
}

int whatsit::doit(const int penalty, const int stain){

  if (!ipvar) {
    cerr << progid
      << " TCPREMOTEIP not set???" << endl;
    // should never happen
    // although you can make it happen using a weird test-harness
    return(ex_syserr);
  }

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

  ipname = dirname + "/" + ipbase;
  struct stat ipstat;
  rslt = stat(ipname.c_str(), &ipstat);
  if (rslt != 0){
    if (errno != ENOENT) {
      cerr << progid << ": stat failed for '"
        << ipname << "' : ";
      perror(0);
    }
    ofstream foo;
    int fd = creat(ipname.c_str(), 0644);
    if (fd < 0){
      cerr << progid << ": create failed for '"
        << ipname << "' : ";
      perror(0);
    }
    close(fd);
    update("new customer", now, now, penalty, stain);
    return(ex_greylisting);
  }

// now for really checking the greylist status:
  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 < 0) {
    update("penalty box", mod_orig, now, penalty, stain);
    return(ex_penaltybox);
  }
  if (mod_age < ac_age){
// when he comes out on parole, he starts over with no reputation:
    update("paroled spammer", now, now, penalty, stain);
    return(ex_greylisting);
  }
  if (mod_age < minimum_age) {
    update("early bird", mod_orig, now, penalty, stain);
    return(ex_greylisting);
  }
  if (mod_age - ac_age < minimum_age    // early bird, or completely unused
    && mod_age > probation) {           // did not diligently resubmit
    update("disprobation", now, now, penalty, stain);
    return(ex_greylisting);
  }
  if (ac_age > maximum_age) {
    update("too old, starting over", now, now, penalty, stain);
    return(ex_greylisting);
  }
// if all checks are passed, must be OK:
  update("returning customer", mod_orig, now, penalty, stain);
  return 0;
}

typedef vector<unsigned char> VU;

class VUx{
public:
  VU addr;
  sa_family_t fam;
  string str();
};

string VUx::str(){
    char msgbuf[INET6_ADDRSTRLEN];
    const char* rslt = inet_ntop(fam, &addr[0],
          msgbuf, sizeof(msgbuf));
    if (!rslt) rslt = "";
    return rslt;
}

VUx parse_sockaddr(const sockaddr* ai_addr) {
    void* numericAddress;
    VUx rslt;
    int addrsize;
    rslt.addr = VU(0);
    rslt.fam = ((sockaddr *)ai_addr)->sa_family;
    switch (rslt.fam) {
    case AF_INET:
      numericAddress = &(((sockaddr_in *)ai_addr)->sin_addr.s_addr);
      addrsize = sizeof(in_addr);
      break;
    case AF_INET6:
      numericAddress = &(((sockaddr_in6 *)ai_addr)->sin6_addr.s6_addr);
      addrsize = sizeof(in6_addr);
      break;
    default:
      cerr << "?Unknown address family " << rslt.fam << endl;
      return rslt;
    }
    unsigned char* foo = (unsigned char*) numericAddress;
    rslt.addr = VU(foo, foo+addrsize);
    return rslt;
}

int diff(const VU aaa, const VU bbb){
  if(aaa.size() != bbb.size()) return 1;
  for (unsigned int ii=0; ii < aaa.size(); ii++){
    if (aaa[ii] != bbb[ii]) return 1;
  }
  return 0;
}

int whatsit::check_dns(){
  string addr("()"), host("()");
  vector<string> checked;
  int sts = check_dns_sub(addr, host, checked);
  if (sts == 0) return sts;
  if (sts != ex_badDNS) return sts;     // possible ex_syserr
#ifndef badDNSfatal
  sts = 0;      // demote badDNS to just a warning
#endif
  cerr << progid;
  if (!sts) cerr << " (warning)";
  cerr << " DNS inconsistency: "
        << addr << " --> "
        << host << " ==>";
  if (!checked.size()) cerr << " ()";
  else for (vector<string>::const_iterator chk = checked.begin();
        chk != checked.end(); chk++) cerr << " " << *chk;
  cerr << endl;

  return sts;
}

int whatsit::check_dns_sub(string &addr, string &host, vector<string> &checked){

#ifdef badDNSfatal
  int ex_dns_fail = ex_syserr;
#else
  int ex_dns_fail = ex_badDNS;
#endif
  struct addrinfo *result;
  struct addrinfo *ipresult;
  struct addrinfo *res;
  addrinfo hints;
  int error;

  memset(&hints, 0, sizeof(struct addrinfo));
#if 1
  // restrict to TCP only; otherwise we get N records per address
  hints.ai_protocol = IPPROTO_TCP;
#endif

  error = getaddrinfo(ipvar, NULL, &hints, &ipresult);
  if (error == EAI_NONAME) return ex_badDNS;
  if (error) {          // some unexpected error
    cerr << progid
      << " odd error " << error
      << "  in getaddrinfo for " << ipvar
      << " : " << gai_strerror(error) << endl;

    return ex_dns_fail;
  }
  if (!ipresult) {
    cerr << "should never happen (addr with no addrs?)" << endl;
    return ex_dns_fail;
  }
  VUx ipAddr = parse_sockaddr(ipresult->ai_addr);
  addr = ipAddr.str();

  char* hostvar = getenv("TCPREMOTEHOST");
  if (hostvar) host = hostvar;
  else return(ex_badDNS);

  error = getaddrinfo(hostvar, NULL, &hints, &result);
  if (error == EAI_NONAME) return ex_badDNS;
  if (error) {
    cerr << progid
      << " error " << error
      << " compare " << EAI_NONAME
      << "  in getaddrinfo for " << ipvar
      << " :: " << gai_strerror(error) << endl;
    return ex_dns_fail;
  }

// loop over all returned results and check for a match.
  for (res = result; res != NULL; res = res->ai_next){
    VUx hostAddr = parse_sockaddr(res->ai_addr);
    checked.push_back(hostAddr.str());
    if (!diff(hostAddr.addr, ipAddr.addr)) {
      ///// cerr << "match! " << ipAddr.addr.size() << endl;
      goto done;
    }
  }
  return ex_badDNS;

done:
  return 0;
}