#!/bin/sh

# Triggered by <Alt><Shift>Left
# as defined in [org/gnome/settings-daemon/plugins/media-keys]
# in ~/.config/gnome-settings/key-bindings.ini
#
# This script makes the screen a bit cooler than it currently is,
# unless it is currently in a ramping phase and not fully tinted
#
# The default warmth is restored at login by ~/.local/bin/restore-gnome

set -eu


# GNOME's GUI lets one choose between 1700 and 4700 only,
# and 6500 is the point where no color correction is applied at all
# while 1000 is the absolute minimum supported by the OS
_MIN_TEMPERATURE=1200
_MAX_TEMPERATURE=4700


notify() {
    ID_FILE="${XDG_RUNTIME_DIR}/night-light-notification-id"
    _id=$(cat "$ID_FILE" 2>/dev/null || true)

    if [ -n "$_id" ]; then
        notify-send -p -t 5000 --replace-id="$_id" "Night Light" "$1" > "$ID_FILE" || rm -f "$ID_FILE"
    else
        notify-send -p -t 5000 "Night Light" "$1" > "$ID_FILE" || rm -f "$ID_FILE"
    fi
}


Schema=org.gnome.settings-daemon.plugins.color


active=$(gdbus call --session \
    --dest org.gnome.SettingsDaemon.Color \
    --object-path /org/gnome/SettingsDaemon/Color \
    --method org.freedesktop.DBus.Properties.Get \
    org.gnome.SettingsDaemon.Color NightLightActive)

applied=$(gdbus call --session \
    --dest org.gnome.SettingsDaemon.Color \
    --object-path /org/gnome/SettingsDaemon/Color \
    --method org.freedesktop.DBus.Properties.Get \
    org.gnome.SettingsDaemon.Color Temperature \
    | sed -E 's/.*uint32 ([0-9]+).*/\1/')

automatic=$(gsettings get $Schema night-light-schedule-automatic)
current=$(gsettings get $Schema night-light-temperature | awk '{print $2}')


# Cooling never turns "Night Light" on
if [ "$active" = "(<false>,)" ]; then
    notify "is not tinting the screen right now (target: ${current}K)"
    exit 0
fi


# While the screen is not (fully) tinted,
# stepping the target has no visible effect
# => Only show what is going on
if [ "$automatic" = "true" ] && [ $((applied - current)) -gt 300 ]; then
    notify "is still following the schedule's ramp (target: ${current}K)"
    exit 0
fi


# Walking past the cool end switches the feature off
if [ "$current" -ge $_MAX_TEMPERATURE ]; then
    gsettings set $Schema night-light-enabled false
    notify "is now off (stepped past ${_MAX_TEMPERATURE}K)"
    exit 0
fi


# 500 = (4700 - 1700 + 500) / 7
# => Seven steps spanning more than the range in the GUI,
#    mainly because we want to allow a bit more warmth (i.e., +500)
new=$((current + 500))

if [ "$new" -gt $_MAX_TEMPERATURE ]; then
    new=$_MAX_TEMPERATURE
fi


gsettings set $Schema night-light-temperature "uint32 $new"