module test_communication_planes_m
    !! Test of module communication_planes_m
    use pfunit
    use MPI
    implicit none
contains

    @test(npes = [4])
    subroutine test_communication_planes(this)
        !! Tests communiacationa among planes with varying dimensions
        use precision_grillix_m, only : GP
        use helpers_m, only : almost_equal
        use communication_planes_m, only : start_comm_planes, &
                                           finalize_comm_planes
        
        class (MpiTestMethod), intent(inout) :: this
        integer :: comm_world, rank, nprocs, ierr
        
        logical :: fine
        integer :: i, k, shift, src
        integer, dimension(2) :: req
        integer :: ndim
        integer, dimension(:), allocatable :: ndim_halos
        real(GP), dimension(:), allocatable :: u, uh
        real(GP) :: rval
        
        comm_world = this%getMpiCommunicator()
        call MPI_comm_rank(comm_world, rank, ierr)
        call MPI_comm_size(comm_world, nprocs, ierr)

        if (rank == 0) then     
            write(*,*)''
            write(*,*)''
            write(*,'(A80)')'test_communication_planes -------------------------------------------------'
        endif

        ! Create some dimensions
        ndim = 5 + rank*(-1)**rank
        allocate(ndim_halos(0:nprocs-1))
        do k = 0, nprocs-1
            ndim_halos(k) = 5 + k*(-1)**k
        enddo
        
        ! Creat some data
        allocate(u(ndim))
        do i = 1, ndim
            u(i) = 1.0_GP*(10*rank + i)
        enddo
        
        ! Test communication with several planes
        do shift = -2*nprocs, 2*nprocs
            src = rank + shift
            src = modulo(src, nprocs)
            allocate(uh(ndim_halos(src)))
            call start_comm_planes(comm_world, ndim, ndim_halos(src), u, shift, uh, req)
            call finalize_comm_planes(req)
            do i = 1, ndim_halos(src)
                rval = 1.0_GP * (10 * src + i)
                fine = almost_equal(uh(i), rval, rtol = 0.0_GP, atol = 1.0E-10_GP) 
                @assertTrue(fine)
            enddo
            deallocate(uh)
        enddo        
        
        if (rank == 0) then     
            write(*,'(A80)')'test_communication_planes complete ----------------------------------------'
            write(*,*)''
            write(*,*)''
        endif

    end subroutine
    
end module