#compdef t

_t() {
  local curcontext="$curcontext" state line
  typeset -A opt_args

  _arguments \
      '1: :->t_command'\
      '2: :->first_arg'

  case $state in
  t_command)
    compadd "$@" archive backend configure display edit in kill\
                 list now out resume sheet week month
  ;;

  first_arg)
    # If the first argument starts with s or d (sheet or display),
    # the second argument can be autocompleted to one of the existing
    # non-archived sheets.
    if [[ $words[2] == s* || $words[2] == d* ]]; then
      t l --all --flat | while read sheet; do
        compadd "$@" $sheet
      done
    fi
  ;;
  esac
}

_t "$@"