/* Operating Systems Spring 2005
   Sample TCP sockets client

   This client sends requests to a server that can lookup 
   user's names given either a username or userid.

  The complete protocol is described in the file PROTOCOL
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h> /* socket specific definitions */
#include <netinet/in.h> /* INET constants and stuff */
#include <arpa/inet.h>  /* IP address conversion stuff */
#include <netdb.h>	    /* gethostbyname */
#include <string.h>
#include <ctype.h>

#include "getline.h"	


/* here is code that attempts to create a tcp socket
   and connect to the server specified.
   No data is read or sent, this just creates the 
   socket and connects to the server

   If everything works, this function returns a socket descriptor.
   Any errors are considered fatal (program exits).
*/

int create_tcp_connection(char *server_hostname,int port) {
  int sd;
  struct sockaddr_in skaddr;
  struct hostent *hp;           /* used for name lookup */

  /* create a socket
     IP protocol family (PF_INET)
     TCP protocol (SOCK_STREAM)
  */

  if ((sd = socket( PF_INET, SOCK_STREAM, 0 )) < 0) {
    perror("Problem creating socket");
    exit(1);
  }

  /* fill in an address structure that will be used to specify
     the address of the server we want to connect to
     address family is IP  (AF_INET)
     server IP address is found by calling gethostbyname with the
     name of the server 
  */
  skaddr.sin_family = AF_INET;

  /* convert hostname to a network byte order binary IP address */
  /* First try to convert using gethostbyname */
  if ((hp = gethostbyname(server_hostname))!=0) {

    /* Name lookup was successful - copy the IP address */
    memcpy( &skaddr.sin_addr.s_addr, hp->h_addr, hp->h_length);

  } else {
 
    /* Name lookup didn't work, try converting from dotted decimal */

    if (inet_aton(server_hostname,&skaddr.sin_addr)==0) {
      printf("Invalid IP address: %s\n",server_hostname);
      exit(1);
    }
  }
 
  /* port must be in network byte order! */
  skaddr.sin_port = htons(port);

  /* attempt to establish a connection with the server */
  if (connect(sd,(struct sockaddr *) &skaddr,sizeof(skaddr)) < 0 ) {
    perror("Problem connecting to server");
    exit(1);
  }
                                        
  return(sd);
}

/* Send a request */

int send_request(int server, char *type, char *arg) {
  char buff[100];
  /* build the request line */
  if (snprintf(buff,100,"%s %s\n",type,arg)>=100) {
	printf("Can't send - request is too long\n");
	exit;
  }

  return(writeline(server,buff));
}




/* When running the client, it must specify 3 command line values:
    server hostname or IP address
	server port number
	either a username or userid

	The client determines whether the request should be a
	username or userid request depending on whether the first
	character of the 3 argument is numeric
*/

int main(int argc, char **argv) {
  char *servername=NULL;
  int port=0;
  int sd;
  char buff[100];


  if (argc!=4) {
	printf("usage: ./client server port username|userid\n");
	return(1);
  }

  servername = argv[1];
  port = atoi(argv[2]);
  
  /* connect to the server */
  sd = create_tcp_connection(servername, port);

  /* determine whether this is a username or userid request */
  if (isdigit(argv[3][0])) {
	/* first char is numeric - must be a userid */
	if (send_request(sd,"userid",argv[3])<0) {
	  printf("Error sending request\n");
	  exit(1);
	}
  } else {
	/* send username request */
	if (send_request(sd,"username",argv[3])<0) {
	  printf("Error sending request\n");
	  exit(1);
	}
  }


  /* get the response */
  if (getline(sd,buff,100)<0) {
	printf("Error reading response\n");
	exit(1);
  }
  if (strncmp(buff,"ERR",3)==0) {
	printf("Server indicates an error: %s\n",buff+3);
  } else if (strncmp(buff,"OK",2)==0) {
	printf("Success: %s\n",buff+2);
  } else {
	printf("Unknown response: %s\n",buff);
  }
  return(1);
}