/* master.c
 *
 * By Jonathan Marks
 * j-marks@uiuc.edu
 *
 * Compiling:
 *    Solaris: cc master.c -o master -lxnet
 *        AIX: cc master.c -o master
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <syslog.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <ctype.h>
#include <netinet/in.h>
#include <errno.h>
#include <arpa/inet.h>

#include <netdb.h>  /* For gethostbyname() */

#define SERVER_PORT 10000
#define CFG_FILE    "servers"

typedef struct {
  int fd;                 /* File descriptor for server       */
  char *servername;       /* Name of server                   */
  struct in_addr address; /* Net-byte-order address for host. */
} server_def;

int n_server_defs = 0;
server_def *server_table = NULL;

int read_config_file() {

  char buf[1024];
  char s_serverName[1024];
  FILE *f_cfg;
  struct hostent *he_server;
  
  if (!(f_cfg = fopen(CFG_FILE, "r"))) {
    fprintf(stderr, "Can't open config file: %s\n",
	    strerror(errno));
    return 0;
  }

  while(fgets(buf, sizeof(buf), f_cfg)) {
    if (sscanf(buf, "%s", s_serverName) < 1) {
      fprintf(stderr, "REJECTED config file line: %s\n", buf);
      continue;
    }

    /* Strip newline */
    if (s_serverName[strlen(s_serverName) - 1] == '\n')
      s_serverName[strlen(s_serverName) - 1] = '\0';

    if (!(he_server = gethostbyname(s_serverName))) {
      fprintf(stderr, 
	      "REJECTED server %s: Can't look it up.\n", s_serverName);
      continue;
    }

    n_server_defs++;
    server_table = (server_def*)
      realloc(server_table, sizeof(server_def) * n_server_defs);
    server_table[n_server_defs - 1].servername = strdup(s_serverName);
    server_table[n_server_defs - 1].address =
      *((struct in_addr*)(he_server->h_addr_list[0]));
    server_table[n_server_defs - 1].fd = -1;

    fprintf(stderr, "ACCEPTED server %s (%s)\n", s_serverName,
	   inet_ntoa(server_table[n_server_defs - 1].address));
  }

  if (n_server_defs)
    return 1;

  return 0;
}


void give_go_signal(void) {

  int i;

  for(i=0; i<n_server_defs; i++)
    if (server_table[i].fd > 0)
      if(write(server_table[i].fd, "go\n", 3) < 0) {
	fprintf(stderr, "ERROR sending GO signal to %s: %s\n",
		server_table[i].servername, strerror(errno));
	close(server_table[i].fd);
	server_table[i].fd = -1;
      }

  return;
}



void give_stop_signal(void) {

  int i;

  for(i=0; i<n_server_defs; i++)
    if (server_table[i].fd > 0)
      if(write(server_table[i].fd, "stop\n", 5) < 0) {
	fprintf(stderr, "ERROR sending STOP signal to %s: %s\n",
		server_table[i].servername, strerror(errno));
	close(server_table[i].fd);
	server_table[i].fd = -1;
      }

  return;
}



void take_user_commands(void) {

  char s_inp[100];
  int more_commands = 1;

  while(more_commands) {

    printf("(h for help)>>> ");
    fgets(s_inp, sizeof(s_inp), stdin);
    if (s_inp[strlen(s_inp) - 1] == '\n')
      s_inp[strlen(s_inp) - 1] = '\0';

    if (!strcmp(s_inp, "h")) {
      /* Show help */
      printf("\th\t\tShow help\n");
      printf("\tgo\t\tGive GO signal to all servers.\n");
      printf("\tstop\t\tGive STOP signal to all servers, then quit.\n");
      printf("\tquit\t\tQuit (without stopping servers.\n");
    }
    else if (!strcmp(s_inp, "go")) {
      give_go_signal();
    }
    else if (!strcmp(s_inp, "stop")) {
      /* Stop servers and quit */
      give_stop_signal();
      more_commands = 0;
    }
    else if (!strcmp(s_inp, "quit")) {
      /* Exit without stopping servers */
      more_commands = 0;
    }
    else {
      /* Don't know what they typed */
      printf("Sorry, unrecognized command. Type 'h' for help.\n");
    }
  }

  return;
}



int main(int argc, char *argv[]) {

  int i;
  struct sockaddr_in sa_server;
  
  if (!read_config_file()) {
    fprintf(stderr, "No server definitions. Exiting.\n");
    return 1;
  }

  /* Open connections to each server */
  for(i=0; i<n_server_defs; i++) {
    int fd_tmp, j;

    printf("Connecting to %s..\n", server_table[i].servername);
    
    if ((fd_tmp = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
      fprintf(stderr, "Can't create a socket for a server: %s\n",
	      strerror(errno));
      for(j=0; j<i; j++)
	close(server_table[i].fd);
      return 1;
    }

    bzero(&sa_server, sizeof(sa_server));
    sa_server.sin_family = AF_INET;
    sa_server.sin_port   = htons(SERVER_PORT);
    sa_server.sin_addr = server_table[i].address;
    if (connect(fd_tmp, (struct sockaddr*) &sa_server,
		sizeof(sa_server)) < 0) {
      fprintf(stderr, "Can't connect to server %s: %s. Aborting.\n",
	      server_table[i].servername, strerror(errno));
      for(j=0; j<i; j++)
	close(server_table[j].fd);
      close(fd_tmp);
      return 1;
    }

    server_table[i].fd = fd_tmp;
  }

  printf("Connected to all servers.\n");

  take_user_commands(); /* command reading loop. */

  for(i=0; i<n_server_defs; i++)
    close(server_table[i].fd);
  
  return 0;
}