/* 
Serval Distributed Numbering Architecture (DNA)
Copyright (C) 2010 Paul Gardner-Stephen 

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
*/


#include <assert.h>
#include <dirent.h>
#include <signal.h>
#include <unistd.h>
#include <time.h>
#include <libgen.h>
#include <sys/socket.h>
#include <sys/stat.h>

#include "serval.h"
#include "conf.h"
#include "strbuf.h"
#include "strbuf_helpers.h"
#include "overlay_interface.h"
#include "overlay_packet.h"
#include "server.h"
#include "keyring.h"

#define PROC_SUBDIR	  "proc"
#define PIDFILE_NAME	  "servald.pid"
#define STOPFILE_NAME	  "servald.stop"

int serverMode = 0;
keyring_file *keyring=NULL;

static char pidfile_path[256];
static int server_getpid = 0;
static int server_write_pid();
static int server_unlink_pid();
static void signal_handler(int signal);
static void serverCleanUp();

/** Return the PID of the currently running server process, return 0 if there is none.
 */
int server_pid()
{
  char dirname[1024];
  if (!FORMF_SERVAL_RUN_PATH(dirname, NULL))
    return -1;
  struct stat st;
  if (stat(dirname, &st) == -1)
    return WHYF_perror("stat(%s)", alloca_str_toprint(dirname));
  if ((st.st_mode & S_IFMT) != S_IFDIR)
    return WHYF("Not a directory: %s", dirname);
  const char *ppath = server_pidfile_path();
  if (ppath == NULL)
    return -1;
  const char *p = strrchr(ppath, '/');
  assert(p != NULL);
  FILE *f = fopen(ppath, "r");
  if (f == NULL) {
    if (errno != ENOENT)
      return WHYF_perror("fopen(%s,\"r\")", alloca_str_toprint(ppath));
  } else {
    char buf[20];
    int pid = (fgets(buf, sizeof buf, f) != NULL) ? atoi(buf) : -1;
    fclose(f);
    if (pid > 0 && kill(pid, 0) != -1)
      return pid;
    INFOF("Unlinking stale pidfile %s", ppath);
    unlink(ppath);
  }
  return 0;
}

const char *_server_pidfile_path(struct __sourceloc __whence)
{
  if (!pidfile_path[0]) {
    if (!FORMF_SERVAL_RUN_PATH(pidfile_path, PIDFILE_NAME))
      return NULL;
  }
  return pidfile_path;
}

int server()
{
  IN();
  serverMode = SERVER_RUNNING;

  // Warn, not merely Info, if there is no configured log file.
  logLevel_NoLogFileConfigured = LOG_LEVEL_WARN;

  /* Catch SIGHUP etc so that we can respond to requests to do things, eg, shut down. */
  struct sigaction sig;
  sig.sa_handler = signal_handler;
  sigemptyset(&sig.sa_mask); // Block the same signals during handler
  sigaddset(&sig.sa_mask, SIGHUP);
  sigaddset(&sig.sa_mask, SIGINT);
  sig.sa_flags = 0;
  sigaction(SIGHUP, &sig, NULL);
  sigaction(SIGINT, &sig, NULL);

  /* Setup up client API sockets before writing our PID file
     We want clients to be able to connect to our sockets as soon 
     as servald start has returned. But we don't want servald start
     to take very long. 
     Try to perform only minimal CPU or IO processing here.
  */
  if (overlay_mdp_setup_sockets()==-1)
    RETURN(-1);
  
  if (monitor_setup_sockets()==-1)
    RETURN(-1);
  
  // start the HTTP server if enabled
  if (httpd_server_start(HTTPD_PORT, HTTPD_PORT_MAX)==-1)
    RETURN(-1);
 
  /* For testing, it can be very helpful to delay the start of the server process, for example to
   * check that the start/stop logic is robust.
   */
  const char *delay = getenv("SERVALD_SERVER_START_DELAY");
  if (delay){
    time_ms_t milliseconds = atoi(delay);
    INFOF("Sleeping for %"PRId64" milliseconds", (int64_t) milliseconds);
    sleep_ms(milliseconds);
  }
  
  /* record PID file so that servald start can return */
  if (server_write_pid())
    RETURN(-1);
  
  overlay_queue_init();
  
  time_ms_t now = gettime_ms();
  
  // Periodically check for server shut down
  RESCHEDULE(&ALARM_STRUCT(server_shutdown_check), now, now+30000, now);
  
  overlay_mdp_bind_internal_services();
  
  olsr_init_socket();

  /* Calculate (and possibly show) CPU usage stats periodically */
  RESCHEDULE(&ALARM_STRUCT(fd_periodicstats), now+3000, now+30000, TIME_MS_NEVER_WILL);

  cf_on_config_change();
  
  // log message used by tests to wait for the server to start
  INFO("Server initialised, entering main loop");
  
  /* Check for activitiy and respond to it */
  while((serverMode==SERVER_RUNNING) && fd_poll())
    ;
  serverCleanUp();
  
  /* It is safe to unlink the pidfile here without checking whether it actually contains our own
   * PID, because server_shutdown_check() will have been executed very recently (in fd_poll()), so
   * if the code reaches here, the check has been done recently.
   */
  server_unlink_pid();
  serverMode = 0;
  RETURN(0);
  OUT();
}

static int server_write_pid()
{
  /* Record PID to advertise that the server is now running */
  const char *ppath = server_pidfile_path();
  if (ppath == NULL)
    return -1;
  FILE *f = fopen(ppath, "w");
  if (!f)
    return WHYF_perror("fopen(%s,\"w\")", alloca_str_toprint(ppath));
  server_getpid = getpid();
  fprintf(f,"%d\n", server_getpid);
  fclose(f);
  return 0;
}

static int server_unlink_pid()
{
  /* Remove PID file to indicate that the server is no longer running */
  const char *ppath = server_pidfile_path();
  if (ppath == NULL)
    return -1;
  if (unlink(ppath) == -1)
    WHYF_perror("unlink(%s)", alloca_str_toprint(ppath));
  return 0;
}

static int get_proc_path(const char *path, char *buf, size_t bufsiz)
{
  if (!formf_serval_run_path(buf, bufsiz, PROC_SUBDIR "/%s", path))
    return -1;
  return 0;
}

int server_write_proc_state(const char *path, const char *fmt, ...)
{
  char path_buf[400];
  if (get_proc_path(path, path_buf, sizeof path_buf)==-1)
    return -1;
    
  size_t dirsiz = strlen(path_buf) + 1;
  char dir_buf[dirsiz];
  strcpy(dir_buf, path_buf);
  const char *dir = dirname(dir_buf); // modifies dir_buf[]
  if (mkdirs_info(dir, 0700) == -1)
    return WHY_perror("mkdirs()");
  
  FILE *f = fopen(path_buf, "w");
  if (!f)
    return WHY_perror("fopen()");
  
  va_list ap;
  va_start(ap, fmt);
  vfprintf(f, fmt, ap);
  va_end(ap);
  
  fclose(f);
  return 0;
}

int server_get_proc_state(const char *path, char *buff, size_t buff_len)
{
  char path_buf[400];
  if (get_proc_path(path, path_buf, sizeof path_buf)==-1)
    return -1;
  
  FILE *f = fopen(path_buf, "r");
  if (!f)
    return -1;
  
  int ret=0;
  
  if (!fgets(buff, buff_len, f))
    ret = WHY_perror("fgets");
  
  fclose(f);
  return ret;
}

/* Called periodically by the server process in its main loop.
 */
DEFINE_ALARM(server_config_reload);
void server_config_reload(struct sched_ent *alarm)
{
  switch (cf_reload_strict()) {
  case -1:
    WARN("server continuing with prior config");
    break;
  case 0:
    break;
  default:
    INFO("server config reloaded");
    break;
  }
  switch (reload_mdp_packet_rules()) {
  case -1:
    WARN("server continuing with prior packet filter rules");
    break;
  case 0:
    break;
  default:
    INFO("server packet filter rules reloaded");
    break;
  }
  if (alarm) {
    time_ms_t now = gettime_ms();
    RESCHEDULE(alarm, 
        now+config.server.config_reload_interval_ms,
	TIME_MS_NEVER_WILL,
	now+config.server.config_reload_interval_ms+100);
  }
}

/* Called periodically by the server process in its main loop.
 */
DEFINE_ALARM(server_watchdog);
void server_watchdog(struct sched_ent *alarm)
{
  if (config.server.watchdog.executable[0]) {
    const char *argv[2];
    argv[0] = config.server.watchdog.executable;
    argv[1] = NULL;
    strbuf argv_sb = strbuf_append_argv(strbuf_alloca(1024), 1, argv);
    switch (fork()) {
    case 0: {
      /* Child, should fork() again to create orphan process. */
      pid_t watchdog_pid;
      switch (watchdog_pid = fork()) {
      case 0:
	/* Grandchild, should exec() watchdog. */
	close_log_file();
	signal(SIGTERM, SIG_DFL);
	close(0);
	close(1);
	close(2);
	execv(config.server.watchdog.executable, (char **)argv);
	// Don't use FATALF_perror() because we want to use _exit(2) not exit(2).
	LOGF_perror(LOG_LEVEL_FATAL, "execv(%s, [%s])",
	    alloca_str_toprint(config.server.watchdog.executable),
	    strbuf_str(argv_sb)
	  );
	break;
      case -1:
	/* grandchild fork failed */
	WHY_perror("fork");
	break;
      default:
	/* Child, report grandchild's PID. */
	if (config.debug.watchdog)
	  LOGF(LOG_LEVEL_DEBUG, "STARTED WATCHDOG pid=%u executable=%s argv=[%s]",
	      watchdog_pid,
	      alloca_str_toprint(config.server.watchdog.executable),
	      strbuf_str(argv_sb)
	    );
	do { _exit(0); } while (1);
	break;
      }
      do { _exit(-1); } while (1);
      break;
    }
    case -1:
      /* child fork failed */
      WHY_perror("fork");
      break;
    }
  }
  if (alarm) {
    time_ms_t now = gettime_ms();
    RESCHEDULE(alarm, 
      now+config.server.watchdog.interval_ms, 
      now+config.server.watchdog.interval_ms, 
      now+100);
  }
}

DEFINE_ALARM(rhizome_open_db);
void rhizome_open_db(struct sched_ent *UNUSED(alarm))
{
  if (config.rhizome.enable && !rhizome_db){
    rhizome_opendb();
    if (config.rhizome.clean_on_start && !config.rhizome.clean_on_open)
      rhizome_cleanup(NULL);
  }
}

void cf_on_config_change()
{
  if (!serverMode)
    return;
  
  time_ms_t now = gettime_ms();
  
  dna_helper_start();
  directory_service_init();
  
  // check for interfaces at least once after config change
  RESCHEDULE(&ALARM_STRUCT(overlay_interface_discover), now, now, now);
  
  if (link_has_neighbours())
    // send rhizome sync periodically
    RESCHEDULE(&ALARM_STRUCT(rhizome_sync_announce), 
      now+1000, now+1000, TIME_MS_NEVER_WILL);

  if (config.server.watchdog.executable[0])
    RESCHEDULE(&ALARM_STRUCT(server_watchdog), 
      now+config.server.watchdog.interval_ms, 
      now+config.server.watchdog.interval_ms, 
      now+100);
  
  // Periodically check for modified configuration
  RESCHEDULE(&ALARM_STRUCT(server_config_reload), 
    now+config.server.config_reload_interval_ms,
    TIME_MS_NEVER_WILL,
    now+config.server.config_reload_interval_ms+100);

  if (config.rhizome.enable){
    RESCHEDULE(&ALARM_STRUCT(rhizome_open_db), now+100, now+100, TIME_MS_NEVER_WILL);
  }else if(rhizome_db){
    rhizome_close_db();
  }
}

/* Called periodically by the server process in its main loop.
 */
DEFINE_ALARM(server_shutdown_check);
void server_shutdown_check(struct sched_ent *alarm)
{
  // TODO we should watch a descriptor and quit when it closes
  /* If this server has been supplanted with another or Serval has been uninstalled, then its PID
      file will change or be unaccessible.  In this case, shut down without all the cleanup.
      Perform this check at most once per second.  */
  static time_ms_t server_pid_time_ms = 0;
  time_ms_t now = gettime_ms();
  if (server_pid_time_ms == 0 || now - server_pid_time_ms > 1000) {
    server_pid_time_ms = now;
    if (server_pid() != server_getpid) {
      WARNF("Server pid file no longer contains pid=%d -- shutting down without cleanup", server_getpid);
      exit(1);
    }
  }
  if (alarm){
    RESCHEDULE(alarm, now+1000, now+30000, now+1100);
  }
}

static void clean_proc()
{
  char path_buf[400];
  if (FORMF_SERVAL_RUN_PATH(path_buf, PROC_SUBDIR)) {
    DIR *dir;
    struct dirent *dp;
    if ((dir = opendir(path_buf)) == NULL) {
      WARNF_perror("opendir(%s)", alloca_str_toprint(path_buf));
      return;
    }
    while ((dp = readdir(dir)) != NULL) {
      if (FORMF_SERVAL_RUN_PATH(path_buf, PROC_SUBDIR "/%s", dp->d_name)) {
	struct stat st;
	if (lstat(path_buf, &st) == -1)
	  WARNF_perror("stat(%s)", path_buf);
	else if (S_ISREG(st.st_mode))
	  unlink(path_buf);
      }
    }
    closedir(dir);
  }
}

static void serverCleanUp()
{
  assert(serverMode);
  rhizome_close_db();
  dna_helper_shutdown();
  overlay_interface_close_all();
  overlay_mdp_clean_socket_files();
  clean_proc();
}

void signal_handler(int signal)
{
  switch (signal) {
    case SIGHUP:
    case SIGINT:
      /* Trigger the server to close gracefully after any current alarm has completed. 
         If we get a second signal, exit now.
      */
      if (serverMode==SERVER_RUNNING){
	INFO("Attempting clean shutdown");
	serverMode=SERVER_CLOSING;
	return;
      }
    default:
      LOGF(LOG_LEVEL_FATAL, "Caught signal %s", alloca_signal_name(signal));
      LOGF(LOG_LEVEL_FATAL, "The following clue may help: %s", crash_handler_clue); 
      dump_stack(LOG_LEVEL_FATAL);
  }
  
  serverCleanUp();
  exit(0);
}