#!/bin/bash

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

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

  # Calculate 5% of the available space, and ensure it's within the limits (max 30GB)
  swap_size=$((available_space * 5 / 100 / 1024)) # Convert MB to GB
  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..."

  # Remove existing swapfile if it exists
  if [ -f /swapfile ]; then
      sudo swapoff /swapfile
      sudo rm /swapfile
      echo "Existing swapfile removed."
  fi

  # 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."
}

# Function to persist the swap file across reboots
persist_swapfile() {
  echo "/swapfile none swap sw 0 0" | sudo tee -a /etc/fstab
  echo "Swap file added to /etc/fstab."
}

# Check if --persist flag is passed
persist=false
if [ "$1" == "--persist" ]; then
  persist=true
fi

# Main script execution
create_swapfile

if [ "$persist" = true ]; then
  persist_swapfile
else
  echo "Swap file will not persist after reboot."
fi

# Show current swap status
sudo swapon --show