#!/usr/bin/env bash

OUTPUT="eDP-1-1"
STEP=0.1
STATE="${XDG_RUNTIME_DIR:-/tmp}/xrandr-redshift"

if [[ -f "$STATE" ]]; then
    GAMMA=$(cat "$STATE")
else
    GAMMA=1.0
fi

case "$1" in
    up)
        GAMMA=$(awk -v g="$GAMMA" -v s="$STEP" 'BEGIN {
            g -= s
            if (g < 0.1) g = 0.1
            printf "%.1f", g
        }')
        ;;
    down)
        GAMMA=$(awk -v g="$GAMMA" -v s="$STEP" 'BEGIN {
            g += s
            if (g > 1.0) g = 1.0
            printf "%.1f", g
        }')
        ;;
esac

echo "$GAMMA" > "$STATE"
xrandr --output "$OUTPUT" --gamma "1.0:${GAMMA}:${GAMMA}"