#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <sys/time.h>
#include <sys/resource.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <syslog.h>
#include <errno.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>

#include "tcp_listen.h"
#include "signal.h"
#include "ssl.h"
#include "strlcpy.h"

static char * port = NULL;
static int become_daemon = 0;
const char * pidfile = "/var/run/akpop3d.pid";
const char * ssl_certfile = "/etc/akpop3d/cert.pem";
const char * ssl_keyfile = "/etc/akpop3d/key.pem";
const char * authfile = NULL;
const char * local_mbox = NULL;
const char * tmp_dir = "/tmp";
char * mailspool = "/var/mail/";
int use_pop3_allow_deny = 0;
int enable_mysql = 0;
unsigned int timeout = 30;


/* mysql pointers */
extern char *HOSTNAME;
extern char *USERNAME;
extern char *PASSWORD;
extern char *DATABASE;
extern char *TABLE;

int daemonize(void);
void pop3_session(int fd);
static void delete_pid(void);

static void sig_chld(int signo) {
  pid_t pid;
  int stat;
  while ((pid = waitpid(-1,&stat,WNOHANG)) > 0);
}

static void sig_term(int signo) {
  if (become_daemon) delete_pid();
  exit(0);
}

static void usage(char * argv0) {
  printf("Usage: %s [OPTIONS]\n", argv0);
  printf("Start a POP3 daemon.\n"
    "\n"
    "  -d             run as a daemon (in the background)\n"
    "  -f <pidfile>   store process ID in <pidfile> (must be a full path)\n"
    "  -s             use SSL for all connections\n"
    "  -c <certfile>  use <certfile> for SSL certificate [%s]\n"
    "  -k <keyfile>   use <keyfile> for SSL RSA key      [%s]\n"
    "  -p <port>      listen on <port>    [default: 110, or 995 if SSL]\n",
    ssl_certfile, ssl_keyfile
  );
  printf(
    "  -l <address>   listen on <address> [default: any]\n"
    "  -a <authfile>  use text file <authfile> for authentication\n"
    "  -m <spooldir>  use directory <spooldir> as mail spool\n"
    "  -D             use /etc/pop3.{allow,deny} files\n"
    "  -L <mbox>      use ~/<mbox> as mail spool\n"
    "  -t <timeout>   use <timeout> seconds as r/w timeout\n"
#ifdef HAVE_LIBMYSQLCLIENT
    "  -M             enable MySQL support\n"
    "  -H <mysqlhost> MySQL support: connect to <mysqlhost>\n"
    "  -U <mysqluser> MySQL support: use username <mysqluser>\n"
    "  -P <mysqlpass> MySQL support: use password <mysqlpass>\n"
    "  -I <mysqldb>   MySQL support: use database <mysqldb>\n"
    "  -T <mysqltbl>  MySQL support: use table <mysqltbl>\n"
#endif /* HAVE_LIBMYSQLCLIENT */
    "\n"
    "Use `%s -v' to show the program version.\n",
    argv0
  );
  exit(EXIT_SUCCESS);
}

static void write_pid(void) {
  FILE * f = fopen(pidfile,"w+");
  if (f) {
    fprintf(f,"%u",getpid());
    fclose(f);
  }
  /* ignore errors */
}

static void delete_pid(void) {
  unlink(pidfile);
}

int main(int argc, char * argv[]) {
  int listenfd, connfd;
  pid_t childpid;
  struct stat sbuf;
  socklen_t addrlen;
#ifdef HAVE_LIBMYSQLCLIENT
  const char * optstring = "df:sp:c:k:l:a:m:hvDL:MH:U:P:I:T:t:x:";
  int len = 0;
#else
  const char * optstring = "df:sp:c:k:l:a:m:hvDL:t:x:";
#endif
  char * listenhost = NULL;
  char * progname;
  int c;
  socklen_t clen;
  struct sockaddr_in client;
#ifdef HAVE_LIBMYSQLCLIENT
  struct rlimit memlim, cpulim;

  /* ok, set some limits here */
  cpulim.rlim_cur = 60;
  cpulim.rlim_max = 60;
  memlim.rlim_cur = 52428800;
  memlim.rlim_max = 52428800;

  if ( setrlimit( RLIMIT_CPU, &cpulim ) != 0 )
	fprintf( stderr, "cpu limit failed" );

  if ( setrlimit( RLIMIT_DATA, &memlim ) != 0 )
    fprintf( stderr, "mem limit failed" );
#endif

  do {
    c = getopt(argc,argv,optstring);
    if (c < 0) continue;
    switch (c) {
      case 'd': become_daemon = 1; break;
      case 'f': pidfile = optarg; break;
      case 's':
#if HAVE_LIBSSL
        set_use_ssl(1);
        if (port==NULL)
          port = "995"; /* POP3 over SSL */
#else
        fprintf(stderr,"%s: %s\n", argv[0], "POP3 over SSL not supported");
        exit(EXIT_FAILURE);
#endif
        break;
      case 'p': port = optarg; break;
      case 'c': ssl_certfile = optarg; break;
      case 'k': ssl_keyfile = optarg; break;
      case 'l': listenhost = optarg; break;
      case 'a': authfile = optarg; break;
      case 't': sscanf(optarg,"%u",&timeout); break;
      case 'x': tmp_dir = optarg; break;
      case 'm': if (stat(optarg,&sbuf)!=0) {
                  fprintf(stderr,"%s: %s: %s\n",argv[0], optarg,strerror(errno));
                  exit(EXIT_FAILURE);
                }
                if (!S_ISDIR(sbuf.st_mode)) {
                  fprintf(stderr,"%s: %s is not a directory\n",argv[0],optarg);
                  exit(EXIT_FAILURE);
                }
                /* never allow any acces to optarg[-1] */
                if (strlen(optarg)>0 && optarg[strlen(optarg)-1]!='/') {
                  size_t ms_len = (size_t)strlen(optarg)+2;
                  mailspool = alloca(ms_len);
                  if (mailspool) {
                    snprintf(mailspool,ms_len,"%s/",optarg);
                  } else {
                    fprintf(stderr,"%s: unable to allocate memory on the stack\n",argv[0]);
                    exit(EXIT_FAILURE);
                  }
                } else {
                  mailspool = optarg; 
                }
                break;
      case 'D': use_pop3_allow_deny = 1; break;
      case 'L': local_mbox = optarg; break;
      case 'h': usage(argv[0]); exit(EXIT_SUCCESS);
      case 'v': printf("%s %s\n","akpop3d",VERSION); exit(EXIT_SUCCESS);
#ifdef HAVE_LIBMYSQLCLIENT
      case 'M': enable_mysql = 1; break;
      case 'H': HOSTNAME = optarg; break;
      case 'U': USERNAME = optarg; break;
      case 'P': 
        {
          PASSWORD = alloca((size_t)(strlen(optarg)+1));
          strlcpy(PASSWORD,optarg,strlen(optarg)+1);
          len = strlen(optarg);
          memset(optarg,'\0',len);
          break;
        }
      case 'I': DATABASE = optarg; break;
      case 'T': TABLE = optarg; break;
#endif
      default:
        fprintf(stderr,"%s: %s\n",argv[0],"unknown option - try '-h'");
        exit(EXIT_FAILURE);
    }
  } while (c != -1);

#ifdef HAVE_LIBMYSQLCLIENT
  if (enable_mysql) {
    int found_null = 0;
    if (HOSTNAME == NULL) {
      fprintf(stderr,"%s: please set a MySQL hostname using -H <host>!\n",argv[0]);
      found_null = 1;
    }
    if (USERNAME == NULL) {
      fprintf(stderr,"%s: please set a MySQL username using -U <user>!\n",argv[0]);
      found_null = 1;
    }
    if (DATABASE == NULL) {
      fprintf(stderr,"%s: please set a MySQL database using -D <db>!\n",argv[0]);
      found_null = 1;
    }
    if (PASSWORD == NULL) {
      fprintf(stderr,"%s: please set a MySQL password using -P <pass>!\n",argv[0]);
      found_null = 1;
    }
    if (TABLE == NULL) {
      fprintf(stderr,"%s: please set a MySQL table using -T <table>!\n",argv[0]);
      found_null = 1;
    }
    if (found_null) {
      exit(1);
    }
  }
#endif

  if (port==NULL)
    port = "110";

  if (become_daemon) {
    daemonize();
    write_pid();
  }

  progname = strrchr(argv[0], '/');
  if (progname == NULL) {
    progname = argv[0];
  } else {
    progname++;
  }
  openlog(progname, LOG_PID, LOG_MAIL);

  listenfd = Tcp_listen(listenhost, port, &addrlen);

  Signal(SIGCHLD,sig_chld);

  Signal(SIGTERM,sig_term);
  Signal(SIGINT,sig_term);
  Signal(SIGHUP,sig_term);
  Signal(SIGQUIT,sig_term);

  for (;;) {
    clen = sizeof(struct sockaddr *);

    if ((connfd = accept(listenfd,(struct sockaddr *) &client,&clen)) < 0) {
      if (errno == EINTR) {
        continue;
      } else {
        syslog(LOG_ERR,"%s: %s","failed to accept connection",strerror(errno));
        continue;
      }
    }

    getpeername( connfd, (struct sockaddr *) &client, &clen );

    syslog( LOG_INFO, "Connection from %s:%u", inet_ntoa( client.sin_addr ), ntohs( client.sin_port ) );

    if ((childpid = fork()) == 0) {
      close(listenfd);
      pop3_session(connfd);
      syslog( LOG_INFO, "Connection closed" );
      exit(0);
    } else if (childpid == -1) {
      syslog(LOG_ERR,"%s: %s","fork failed (aborting)",strerror(errno));
    }

    close(connfd);

  }

  /* NOTREACHED */
  return 0;
}