checkbg

#!/usr/bin/env sh
# vim: ft=sh ts=4 sw=4 sts=4 et :
# Check sunrise/sunset and set desktop background accordingly

has() {
    command -v "$1" >/dev/null 2>&1
}

if ! has setbg; then
    echo "Error: setbg is not installed" >&2
    exit 1
fi

# If `sunwait` is installed, use it to determine if it's day or night
if has sunwait; then
    # Get latitude and longitude from ip address using `curl` or `wget`
    # coords format is "latitude,longitude"
    if has curl; then
        coords=$(curl -s ipinfo.io/loc)
    elif has wget; then
        coords=$(wget -qO- ipinfo.io/loc)
    fi

    if [ -n "$coords" ]; then
        # Extract latitude and longitude from coords
        latitude=${coords%,*}
        longitude=${coords#*,}

        # Convert latitude and longitude format from [+-]0.0000 to
        # 0.0000[NS] (latitude) or 0.0000[EW] (longitude)
        case "$latitude" in
        -*)
            latitude="${latitude#-}S"
            ;;
        *)
            latitude="${latitude}N"
            ;;
        esac

        case "$longitude" in
        -*)
            longitude="${longitude#-}W"
            ;;
        *)
            longitude="${longitude}E"
            ;;
        esac

        if [ "$(sunwait poll "$latitude" "$longitude")" = "DAY" ]; then
            setbg light
        else
            setbg dark
        fi
        exit
    fi

    # Let `sunwait` detect the location itself if we cannot get the coordinates
    # from ipinfo.io
    if [ "$(sunwait poll)" = "DAY" ]; then
        setbg light
    else
        setbg dark
    fi
    exit
fi

# Else use current time to determine if it's day or night
current_hour=$(date +%H)
current_hour="${current_hour#0}"
if [ "$current_hour" -gt 6 ] && [ "$current_hour" -lt 18 ]; then
    setbg light
else
    setbg dark
fi