#include <iostream>
#include <string>
#include <cstdlib>
#include <mpi.h>
#include <ctime>
#include "MPI2.h"
using namespace std;

int num_procs, my_proc;
MPI_Request r;
MPI_Status status;

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

    MPI_Init (&argc,&argv);
    MPI_Comm_size (MPI_COMM_WORLD,&num_procs);
    MPI_Comm_rank (MPI_COMM_WORLD,&my_proc);

    srand (time (NULL)+my_proc);  //Give each processor a different random seed

    if (my_proc==0) {
        cout << "Enter a string:  ";
        string s;
        getline (cin,s);
        const char *A = s.c_str();
        MPI_Isend (A,strlen(A)+1,MPI_CHAR,1,42,MPI_COMM_WORLD,&r);
    } else if (my_proc==num_procs-1) {
        char sc[100];
        MPI_Recv (sc,sizeof sc,MPI_CHAR,MPI_ANY_SOURCE,42,MPI_COMM_WORLD,&status);
        string rs (sc);
        cout << my_proc << " received a message from " <<status.MPI_SOURCE << ":  \"" << rs << "\"." << endl;
    } else {
        char sc[100];
        MPI_Recv (sc,sizeof sc,MPI_CHAR,MPI_ANY_SOURCE,42,MPI_COMM_WORLD,&status);
        string rs (sc);
        cout << my_proc << " received a message from " <<status.MPI_SOURCE << ":  \"" << rs << "\"." << endl;
        cout << "Pass It On!" << endl;
        int rr = rand()%rs.length();
        rs[rr] = (rs[rr]+1)%256;
        const char *A = rs.c_str();
        MPI_Isend (A,strlen(A)+1,MPI_CHAR,my_proc+1,42,MPI_COMM_WORLD,&r);
   }
   MPI_Finalize ();
   return 0;
}