#!/bin/sh

INTERVAL=600  # 10 minutes

if [ -f /tmp/last_wallpaper_time ]; then
    last=$(cat /tmp/last_wallpaper_time)
else
    last=$(date +%s)
fi

now=$(date +%s)
elapsed=$((now - last))
remaining=$((INTERVAL - elapsed))

if [ "$remaining" -lt 0 ]; then
    remaining=0
fi

min=$((remaining / 60))
sec=$((remaining % 60))

# Format as mm:ss
printf "%02d:%02d\n" "$min" "$sec"