#!/bin/bash

# Script to update a RHEL-based Linux system, set the timezone, change the hostname,
# add a limited user account, modify sshd_config settings, and optionally install Docker CE

# Variables
timezone="America/New_York"
sshd_config="/etc/ssh/sshd_config"

# Function to prompt for hostname
prompt_for_hostname() {
    read -p "Please enter the desired hostname: " hostname
}

# Function to add hostname and IP to /etc/hosts
update_hosts_file() {
    local ip_address
    ip_address=$(hostname -I | awk '{print $1}')
    echo "Updating /etc/hosts with IP $ip_address and hostname $hostname..."
    
    # Check if the entry already exists
    if grep -q "$ip_address" /etc/hosts; then
        echo "Entry for $ip_address already exists in /etc/hosts."
        sed -i "s/.*$hostname/$ip_address $hostname/" /etc/hosts
    else
        echo "$ip_address $hostname" >> /etc/hosts
        echo "Added $ip_address $hostname to /etc/hosts."
    fi
}

# Function to prompt for Docker installation
prompt_for_docker_install() {
    read -p "Would you like to install Docker CE? (y/n): " install_docker
    if [[ "$install_docker" =~ ^[Yy]$ ]]; then
        install_docker
    else
        echo "Skipping Docker installation."
    fi
}

# Function to install Docker
install_docker() {
    echo "Installing Docker CE..."
    curl -fsSL https://get.docker.com -o get-docker.sh
    sh get-docker.sh

    # Start and enable Docker service
    systemctl start docker
    systemctl enable docker
    echo "Docker installation complete."
}

# Function to create a limited user account
create_user_account() {
    read -p "Please enter the username for the new user account: " username
    read -sp "Please enter the password for the new user account: " password
    echo

    # Create the user and add to the wheel group
    if id "$username" &>/dev/null; then
        echo "User $username already exists."
    else
        useradd -m -G wheel "$username"
        echo "$username:$password" | chpasswd
        echo "User $username created and added to the wheel group."
        
        # Check if Docker is installed and add the user to the docker group
        if command -v docker &> /dev/null; then
            usermod -aG docker "$username"
            echo "User $username added to the docker group."
        fi
    fi
}

# Check if the script is run as root
if [ "$(id -u)" -ne 0 ]; then
    echo "This script must be run as root. Please use sudo or switch to root."
    exit 1
fi

# Update the package manager
echo "Updating package manager..."
if command -v dnf &> /dev/null; then
    dnf -y makecache
elif command -v yum &> /dev/null; then
    yum -y makecache
else
    echo "Neither dnf nor yum found. This script only works on RHEL-based distributions."
    exit 1
fi

# Upgrade installed packages
echo "Upgrading installed packages..."
if command -v dnf &> /dev/null; then
    dnf -y upgrade
elif command -v yum &> /dev/null; then
    yum -y update
fi

# Change the timezone
echo "Setting timezone to $timezone..."
timedatectl set-timezone "$timezone"

# Change the hostname
prompt_for_hostname
echo "Setting hostname to $hostname..."
hostnamectl set-hostname "$hostname"

# Update /etc/hosts
update_hosts_file

# Create a limited user account
create_user_account

# Modify sshd_config
echo "Modifying SSH configuration..."
if [ -f "$sshd_config" ]; then
    # Set PermitRootLogin to no
    sed -i 's/^PermitRootLogin .*/PermitRootLogin no/' "$sshd_config" || echo "PermitRootLogin no" >> "$sshd_config"

    # Set PasswordAuthentication to no
    if grep -q '^#PasswordAuthentication' "$sshd_config"; then
        sed -i 's/^#PasswordAuthentication.*/PasswordAuthentication no/' "$sshd_config"
    else
        sed -i 's/^PasswordAuthentication .*/PasswordAuthentication no/' "$sshd_config" || echo "PasswordAuthentication no" >> "$sshd_config"
    fi

    # Ensure AddressFamily inet is set
    if grep -q '^#AddressFamily' "$sshd_config"; then
        sed -i 's/^#AddressFamily.*/AddressFamily inet/' "$sshd_config"
    else
        sed -i 's/^AddressFamily .*/AddressFamily inet/' "$sshd_config" || echo "AddressFamily inet" >> "$sshd_config"
    fi
else
    echo "sshd_config file not found. Exiting."
    exit 1
fi

# Get the IP address of the machine
ip_address=$(hostname -I | awk '{print $1}')

# Prompt the user to copy their public key
echo "Please copy your public SSH key to the server using the following command:"
echo "ssh-copy-id $username@$ip_address"

# Wait until the authorized_keys file is no longer empty
echo "Waiting for your public key to be copied..."
while true; do
    if [ -s "/home/$username/.ssh/authorized_keys" ]; then
        echo "Public key has been successfully copied."
        break
    fi
    sleep 2
done

# Restart SSH service to apply changes
echo "Restarting SSH service..."
systemctl restart sshd

# Prompt for Docker installation
prompt_for_docker_install

# Clean up
echo "Cleaning up..."
if command -v dnf &> /dev/null; then
    dnf -y autoremove
elif command -v yum &> /dev/null; then
    yum -y autoremove
fi

echo "System update complete! Timezone set to $timezone, hostname set to $hostname, limited user created, sshd_config modified, and Docker installation completed if selected."