#include <stdio.h>
#include <mpi.h>

#define ERR(...) fprintf(stderr, __VA_ARGS__)

int main(int argc, char** argv)
{
    int rc;
    int token;
    MPI_Status status;
    rc = MPI_Init(NULL, NULL);

    if (rc != MPI_SUCCESS)
    {
        ERR("Unable to initialize MPI, aborting...");
        return 0;        
    }

    int world_size;
    MPI_Comm_size(MPI_COMM_WORLD, &world_size);

    int world_rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);

    int neighbor = (world_rank + 1) % world_size;

    printf("[%d/%d] neighbor %d\n", world_rank, world_size, neighbor);
    
    if (world_rank == 0)
    {
        token = 5;
        MPI_Send(&token, 1, MPI_INT, neighbor, 0, MPI_COMM_WORLD);
        MPI_Recv(&token, 1, MPI_INT, MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &status);
    } 
    else
    {
        MPI_Recv(&token, 1, MPI_INT, MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &status);
        printf("[%d/%d] received %d from neighbor :^)\n", world_rank, world_size, token);
        MPI_Send(&token, 1, MPI_INT, neighbor, 0, MPI_COMM_WORLD);
    }

    MPI_Finalize();
    return 0;
}