#include <string>
#include <iostream>
#include <fcntl.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/msg.h>
#include <sys/ipc.h>
#include <errno.h>
#include <unistd.h>
#include "err.h"
#include "mesg.h"

using namespace std;
 
#define MAX_SIZE 80

char MSGKEY[] = "MSGKEY";

struct mymsgbuf {
  long mtype;
  char mtext[MAX_SIZE];
};

void send_message(int qid, struct mymsgbuf *qbuf, long type, char *text)
{
  cout << "Sending a message ..." << endl;
  qbuf->mtype = type;
  strncpy(qbuf->mtext, text, MAX_SIZE);
  qbuf->mtext[MAX_SIZE - 1] = '\0';    /* to null-terminate too long strings */

  if((msgsnd(qid, (struct msgbuf *)qbuf, strlen(qbuf->mtext) + 1, 0)) ==-1) {
    syserr("msgsnd in send_message");
    exit(1);
  }
}

void read_message(int qid, struct mymsgbuf *qbuf, long type)
{
  cout << "Reading a message ..." << endl;
  qbuf->mtype = type;
  if (msgrcv(qid, (struct msgbuf *)qbuf, MAX_SIZE, type, 0) == -1)
    syserr("msgrcv in read_message");

  cout << "Type: " << qbuf->mtype << " Text: " << qbuf->mtext << endl;
}

void remove_queue(int qid)
{
  if (msgctl(qid, IPC_RMID, 0) == -1)
    syserr("msgctl in remove_queue");
}

void change_queue_mode(int qid, char *mode)
{
  struct msqid_ds myq_ds;

  if (msgctl(qid, IPC_STAT, &myq_ds) == -1)	/* Get current info */ 
    syserr("msgctl1 in change_queue_mode");
  sscanf(mode, "%ho", &myq_ds.msg_perm.mode); 	/* Convert and load the mode */
  if (msgctl(qid, IPC_SET, &myq_ds) == -1)	/* Update the mode */
    syserr("msgctl2 in change_queue_mode");
}

void usage(void)
{
  cerr << "msgtool - A utility for tinkering with msg queues" << endl;
  cerr << "USAGE: msgtool (s)end <type> <messagetext>" << endl;
  cerr << "               (r)ecv <type>" << endl;
  cerr << "               (d)elete" << endl;
  cerr << "               (m)ode <octal mode>" << endl;
  exit(1);
}

int main(int argc, char *argv[])
{
  key_t key;
  int   msgq_id;
  struct mymsgbuf qbuf;
  char *key_s;

  if (argc == 1)  usage();
  if ((key_s = getenv(MSGKEY)) == 0)
    fatal("Environtment variable MSGKEY undefined");
  if ((key = atoi(key_s)) == 0)
    fatal("Incorrect key");
  if ((msgq_id = msgget(key, IPC_CREAT | 0660)) == -1)
    syserr("msgget");

  switch(tolower(argv[1][0])) {
    case 's': send_message(msgq_id, &qbuf, atol(argv[2]), argv[3]); break;
    case 'r': read_message(msgq_id, &qbuf, atol(argv[2]));          break;
    case 'd': remove_queue(msgq_id);                                break;
    case 'm': change_queue_mode(msgq_id, argv[2]);                  break;
    default : usage();
  }
  return 0 ;
}