#!/bin/bash

# Function to display warnings
show_warning() {
  echo "##############################################"
  echo "# [WARNING] SYSTEM CONFIGURATION CHANGE      #"
  echo "##############################################"
  echo "Changing hostname:"
  echo "$1"
  echo "--> $2"
  echo "##############################################"
  echo
}

# Initial security check
read -p "WARNING: This script will modify system files. Continue? (y/N) " -n 1 -r
echo
if [[ ! $REPLY =~ ^[Yy]$ ]]; then
  echo "Installation canceled."
  exit 1
fi

# Get current hostname
OLD_HOSTNAME=$(hostname)

# Get new hostname (argument or prompt)
if [[ -z "$1" ]]; then
  read -p "Enter new hostname (Use only letters, numbers, and hyphens.): " NEW_HOSTNAME
else
  NEW_HOSTNAME="$1"
fi

# Validate hostname format
if [[ ! "$NEW_HOSTNAME" =~ ^[a-zA-Z0-9-]{1,63}$ ]]; then
  echo "ERROR: Invalid hostname format. Use only letters, numbers, and hyphens."
  exit 1
fi

# Show change warning
show_warning "$OLD_HOSTNAME" "$NEW_HOSTNAME"

# Final confirmation
read -p "Confirm hostname change? (y/N) " -n 1 -r
echo
if [[ ! $REPLY =~ ^[Yy]$ ]]; then
  echo "Installation canceled."
  exit 1
fi

# Backup files
BACKUP_TIME=$(date +%Y%m%d-%H%M%S)
sudo cp /etc/hostname "/etc/hostname.bak-$BACKUP_TIME"
sudo cp /etc/hosts "/etc/hosts.bak-$BACKUP_TIME"

# Update system files
echo "$NEW_HOSTNAME" | sudo tee /etc/hostname >/dev/null
sudo sed -i "s/127\.0\.1\.1.*/127.0.1.1\t$NEW_HOSTNAME/g" /etc/hosts

# Apply changes
sudo hostnamectl set-hostname "$NEW_HOSTNAME"
sudo systemctl restart avahi-daemon 2>/dev/null || true

# Completion message
echo
show_warning "$OLD_HOSTNAME" "$NEW_HOSTNAME"
echo "Hostname change complete!"
echo "Original files backed up with timestamp: $BACKUP_TIME"
echo "A system reboot is recommended for full propagation."