# goto completion                                          -*- shell-script -*-

_comp_cmd_goto() {
  local cur prev words cword comp_args
  _comp_initialize -- "$@" || return

  # the list of valid options with their argument requirement
  # it is updated as the command is parsed
  local -A valid_opts=([-a]=true [-r]=true [-g]=true [-e]=false [-l]=false [-t]=false)
  # how many positional arguments are expected
  local -i expected_positional_args=1
  # optionals and positionals read up to, not including ${cword} (current word index)
  local -i opt_args=0 positional_args=0
  # holds an option that requires its argument to be read next
  local expected_optarg

  local i word
  for (( i = 1; i < cword; i++ )); do
    word="${words[${i}]}"

    if [[ "${word:0:1}" == '-' ]]; then # reading an option

      # any option is invalid if...
      if \
        (( positional_args > 0 )) || # a positional parameter has been specified \
        [[ -n "${expected_optarg}" ]] || # a previous option is expecting an argument \
        ! [[ -v valid_opts["${word}"] ]] # the option is invalid given the previously provided ones \
      then
        return
      fi

      local arg_required=${valid_opts["${word}"]}

      case "${word:1}" in
        a|r)
          unset -v 'valid_opts[-g]' 'valid_opts[-e]' 'valid_opts[-l]' 'valid_opts[-t]'
          ;;
        g|e|l|t)
          valid_opts=()
          ;;
        *)
          return
          ;;
      esac

      if ${arg_required}; then
        expected_optarg="${word}"
      else
        expected_optarg=
      fi

      expected_positional_args=0

      (( opt_args++ ))
    elif [[ -n "${expected_optarg}" ]]; then
      expected_optarg=
    else
      (( positional_args++ ))

      if (( positional_args > expected_positional_args )); then
        return
      fi
    fi
  done

  if [[ "${cur:0:1}" == '-' ]]; then
    if [[ -z "${expected_optarg}" ]] && (( positional_args == 0 )); then
      _comp_compgen -- -W '"${!valid_opts[@]}"'
    fi
    return
  fi

  if [[ "${prev:0:1}" == '-' ]]; then
    case "${prev:1}" in
      r|g)
        __goto_comp_keys
        ;;
    esac
    return
  fi

  if (( opt_args == 0 && positional_args == 0 )); then
    __goto_comp_keys
  fi
} &&
  complete -F _comp_cmd_goto goto

# ex: filetype=sh