Hook for gammastep that changes between light and dark variants of theme

change-theme.sh

#!/bin/sh

# Rifaz Nahiyan
# https://github.com/rifazn

# Hook for gammastep that changes between light and dark variants of theme
# Place this in $XDG_CONFIG_DIR/gammastep/hooks/
# TODO: if prefers-dark-theme is set to true, don't do anything

set_theme () {
    gsettings set org.gnome.desktop.interface gtk-theme "$1"
}

# Default light variant of theme is set in ~/.config/gtk-3.0/settings.ini
# Set light and dark variants according to that
current_theme="$(gsettings get org.gnome.desktop.interface gtk-theme)"
# this value is contained in ''. So filter that
current_theme="${current_theme:1:-1}"

# current_theme might be the dark variant, so trim that
light_variant="${current_theme%-Dark}"
dark_variant="${light_variant}-Dark"

case "$1" in
    "period-changed")
        # Test some echos
        notify-send "gammastep period change at $(date "+%H:%M")" "$(echo "$@")"
        if [[ "$3" = "night" ]]; then
            set_theme "$dark_variant"
        elif [[ "$3" = "daytime" ]]; then
            set_theme "$light_variant"
        fi
esac