brightness

#!/bin/bash

set -e
set -o pipefail


################################################################################

function error {
    echo "ERROR: ${*}" >/dev/stderr
}

function cmd-exist {
    builtin type -P "${1}" &>/dev/null
}

################################################################################

function read-value {
    local type value

    type="${1}"
    value="${2}"

    { grep -oP "${type} value = +\K\w+" | tr -d '\n'; } <<< "${value}"
}

function get-brightness {
    local value

    value="$(sudo ddcutil getvcp 10)"

    echo -n "Current brightness is "
    read-value current "${value}"
    echo -n '/'
    read-value max     "${value}"
    echo
}

function set-brightness {
    sudo ddcutil setvcp 10 "${1}"
}

################################################################################

function parse-args {
    local opts flags script

    script="$(basename "${0}")"
    flags="help"
    opts="$(getopt -o h --long "${flags}" -n "${script}" -- "${@}")"
    eval set -- "$opts"

    while true; do
        case "${1}" in
            -h | --help)
                usage
                exit
                ;;

            -- ) shift; break ;;
            * ) break ;;
        esac
    done

    case "${1}" in
        ''|*[!0-9]*)
            error "Bad brighness value. Should be 0-10!"
            return 3
            ;;
        *)
            if ! (( 0 < $1 || $1 <= 100 )) ; then
                error "Bad brighness value. Should be 0-10!"
                return 3
            fi

            ARG_BRIGHTNESS="${1}"
            ;;
    esac

    export ARG_BRIGHTNESS
}

function usage {
    cat <<EOM
Usage: $(basename "${0}") <BRIGHTNESS>

Set brightness of external display to 0-10 (in steps of 10%).
EOM

}

function main {
    parse-args "${@}"

    if ! cmd-exist ddcutil; then
        error "Missing ddcutil. Install before proceeding!"
        return 4
    fi

    if [ -v DEBUG  ]; then
        get-brightness
    fi

    set-brightness "${ARG_BRIGHTNESS}"

    if [ -v DEBUG  ]; then
        get-brightness
    fi
}

main "${@}"; exit