__nnictl_cmds="create resume update stop trial webui experiment config rest log"
__nnictl_create_cmds="--config --webuiport"
__nnictl_resume_cmds="--experiment --manager --webuiport"
__nnictl_update_cmds="searchspace concurrency duration"
__nnictl_update_searchspace_cmds="--filename"
__nnictl_update_concurrency_cmds="--value"
__nnictl_update_duration_cmds="--value"
__nnictl_trial_cmds="ls kill"
__nnictl_trial_kill_cmds="--trialid"
__nnictl_webui_cmds="start stop url"
__nnictl_webui_start_cmds="--port"
__nnictl_experiment_cmds="show"
__nnictl_config_cmds="show"
__nnictl_rest_cmds="check"
__nnictl_log_cmds="stdout stderr"
__nnictl_log_stdout_cmds="--tail --head --path"
__nnictl_log_stderr_cmds="--tail --head --path"

__nnictl_remain_args()
{
    ret=${!1}  # ret = $__nnictl_xxx_cmds
    # for arg in COMP_WORDS[:-1]:
    for arg in "${COMP_WORDS[@]::${#COMP_WORDS[@]}-1}"; do
        # remove previously set argument from ret
        if [[ $arg == --* ]]; then
            ret=${ret/$arg/}
        fi
    done
    echo $ret
}

_nnictl()
{
    _words_cnt=${#COMP_WORDS[@]}

    if [ $_words_cnt == 1 ]; then
        # no argument input, list all commands
        complete -W "$_nnictl_cmds"
    elif [ $_words_cnt == 2 ]; then
        # completing frst argument from __nnictl_cmds
        COMPREPLY=($(compgen -W "$__nnictl_cmds" -- "${COMP_WORDS[1]}"))
    elif [ $_words_cnt == 3 ]; then
        # completing second argument from __nnictl_${FirstArg}_cmds
        args=__nnictl_${COMP_WORDS[1]}_cmds
        COMPREPLY=($(compgen -W "${!args}" -- "${COMP_WORDS[2]}"))
    elif [[ ${COMP_WORDS[-2]} != -* ]]; then
        # last argument does not starts with "-", so this one is likely to be "--xxx"
        if [[ ${COMP_WORDS[2]} == -* ]]; then
            # second argument starts with "-", use __nnictl_${FirstArg}_cmds
            args=__nnictl_${COMP_WORDS[1]}_cmds
        else
            # second argument is a word, use __nnictl_${FirstArg}_{SecondArg}_cmds
            args=__nnictl_${COMP_WORDS[1]}_${COMP_WORDS[2]}_cmds
        fi
        # remove already set arguments from candidates
        remain_args=$(__nnictl_remain_args ${args})
        COMPREPLY=($(compgen -W "$remain_args" -- "${COMP_WORDS[-1]}"))
    fi
}

complete -F _nnictl nnictl