program main
   use iso_fortran_env
   use iso_c_binding, only: c_char, c_double, c_int, c_int64_t, c_null_char, &
                            c_size_t, c_carriage_return, c_new_line
   use mod_dill, only: ipaddr, ipaddr_local, ipaddr_port, ipaddr_str, &
                       IPADDR_MAXSTRLEN, IPADDR_IPV4, tcp_accept, tcp_close, &
                       tcp_listen, mrecv, msend, suffix_attach, suffix_detach
   use db
   implicit none

   type(db_type) :: db
   character(len=128):: db_path
   character(len=24):: username
   real(kind=c_double) :: x_pos
   real(kind=c_double) :: y_pos
   integer :: command
   logical :: exist

   integer(c_int) :: connection, rc, socket
   integer(c_size_t) :: message_size, msglen = 256
   character(c_char) :: message(256) = ''
   type(ipaddr) :: addr, addr_remote
   character(kind=c_char, len=IPADDR_MAXSTRLEN) :: address_string = ''
   character(len=*), parameter :: TCP_SUFFIX = c_carriage_return//c_new_line//c_null_char

   call getarg(1, db_path)

   inquire (file=db_path(:Len_Trim(db_path)), exist=exist)
   if (.not. exist) then
      stop 1
   end if

   rc = db_open(db, db_path(:Len_Trim(db_path)))

   rc = ipaddr_local(addr, '127.0.0.1'//c_null_char, 5555_c_int, IPADDR_IPV4)
   call ipaddr_str(addr, address_string)

   print *, 'Listening on socket:'
   print *, '  IP address: ', address_string
   print *, '  Port: ', ipaddr_port(addr)
   print *, '  Opened DB : ', db_path(:Len_Trim(db_path))

   socket = tcp_listen(addr, 0_c_int)

   ! do while not logged out
   server_loop: do

      connection = tcp_accept(socket, addr_remote, -1_c_int64_t)
      call ipaddr_str(addr, address_string)
      print *, 'New connection from '//trim(address_string)
      connection = suffix_attach(connection, TCP_SUFFIX, 2_c_size_t)
      message_size = mrecv(connection, message, msglen, -1_c_int64_t)
      print *, message_size, message

      read (message, "(f8.2, f8.2, i3, a24)") x_pos, y_pos, command, username
      print *, 'username=', username, ' x_pos=', x_pos, ' y_pos=', y_pos, ' command=', command

      if (command .eq. 0) then     ! get all logged in users and return their positions to client
         rc = db_count_logged_in_users(db, connection)
         rc = db_get_logged_in_users(db, connection)
      else if (command .eq. 1) then
         rc = db_login_user(db, username)
         rc = db_count_logged_in_users(db, connection)
         rc = db_get_logged_in_users(db, connection)
      else if (command .eq. 3) then ! update new pos to database
         rc = db_move_user(db, username, x_pos, y_pos)
         rc = db_count_logged_in_users(db, connection)
         rc = db_get_logged_in_users(db, connection)
      else ! (2)  if logout update logged_in to database
         rc = db_logout_user(db, username)
         rc = db_count_logged_in_users(db, connection)
         rc = db_get_logged_in_users(db, connection)
         exit server_loop
      end if
   end do server_loop

   rc = db_close(db)

end program main