#!/bin/bash

# Detect the main disk by finding the partition mounted on root ('/')
main_disk=$(df / | tail -1 | awk '{print $1}')
mount_point=$(df / | tail -1 | awk '{print $6}')

# Get available space on the partition in GB
available_space=$(df -BG $mount_point | tail -1 | awk '{print $4}' | sed 's/G//')

# Calculate 5% of the available space, and ensure it's within the limits (max 30GB)
swap_size=$((available_space * 5 / 100))
if [ $swap_size -gt 30 ]; then
    swap_size=30
elif [ $swap_size -lt 1 ]; then
    echo "Not enough disk space to create a swap file."
    exit 1
fi

echo "Creating a ${swap_size}GB swap file at /swapfile..."

# Create the swap file
sudo fallocate -l ${swap_size}G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile

echo "Swap file of ${swap_size}GB created and activated."

# Ask if the user wants to persist the swap after reboot
read -p "Do you want to persist the swap file after reboot? (y/n): " persist_swap

if [[ "$persist_swap" == "y" || "$persist_swap" == "Y" ]]; then
    echo "/swapfile none swap sw 0 0" | sudo tee -a /etc/fstab
    echo "Swap file added to /etc/fstab."
else
    echo "Swap file will not persist after reboot."
fi

# Show swap summary
sudo swapon --show