#!/bin/bash
#
# https://github.com/xdev-asia-labs/openvpn-install
#
# Copyright (c) 2013 Nyr. Released under the MIT License.
# Copyright (c) 2025 xdev-asia-labs.
#

# Global Variables
LOG_FILE="/var/log/openvpn-install.log"
EASY_RSA_VERSION="3.2.1"
EASY_RSA_URL="https://github.com/OpenVPN/easy-rsa/releases/download/v${EASY_RSA_VERSION}/EasyRSA-${EASY_RSA_VERSION}.tgz"

# Exit Codes
E_SUCCESS=0
E_GENERAL=1
E_DEPENDENCY=3
E_ROOT_REQUIRED=4
E_OS_UNSUPPORTED=5
E_INTERRUPT=130

# Colors
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[0;33m'
NC='\033[0m' # No Color

# --- Logging & Error Handling ---

log() {
	local level="$1"
	shift
	local message="$*"
	local timestamp
	timestamp=$(date "+%Y-%m-%d %H:%M:%S")
	# Ensure log file exists and is writable
	if [[ ! -f "$LOG_FILE" ]]; then
		touch "$LOG_FILE" 2>/dev/null || return
	fi
	echo -e "${timestamp} [${level}] ${message}" >> "$LOG_FILE"
}

log_info() {
	echo -e "${GREEN}[INFO]${NC} $*"
	log "INFO" "$*"
}

log_warn() {
	echo -e "${YELLOW}[WARN]${NC} $*"
	log "WARN" "$*"
}

log_error() {
	echo -e "${RED}[ERROR]${NC} $*" >&2
	log "ERROR" "$*"
}

fatal_error() {
	log_error "$1"
	exit "${2:-$E_GENERAL}"
}

cleanup() {
	# Cleanup temporary files if any
	:
}
trap cleanup EXIT
trap 'fatal_error "Script interrupted." $E_INTERRUPT' INT TERM

# --- Validation Functions ---

validate_ip() {
	local ip="$1"
	if [[ "$ip" =~ ^[0-9]{1,3}(\.[0-9]{1,3}){3}$ ]]; then
		return 0
	fi
	return 1
}

validate_port() {
	local port="$1"
	if [[ "$port" =~ ^[0-9]+$ ]] && [ "$port" -ge 1 ] && [ "$port" -le 65535 ]; then
		return 0
	fi
	return 1
}

is_root() {
	if [[ "$EUID" -ne 0 ]]; then
		return 1
	fi
	return 0
}

check_tun_available() {
	if [[ ! -e /dev/net/tun ]] || ! ( exec 7<>/dev/net/tun ) 2>/dev/null; then
		return 1
	fi
	return 0
}

# --- Main Logic Functions ---

initial_check() {
	# Detect Debian users running the script with "sh" instead of bash
	if readlink /proc/$$/exe | grep -q "dash"; then
		fatal_error 'This installer needs to be run with "bash", not "sh".' $E_DEPENDENCY
	fi

	# Discard stdin
	read -N 999999 -t 0.001

	if ! is_root; then
		fatal_error "This installer needs to be run with superuser privileges." $E_ROOT_REQUIRED
	fi

	if ! check_tun_available; then
		fatal_error "The system does not have the TUN device available. TUN needs to be enabled before running this installer." $E_DEPENDENCY
	fi

	# Detect OS
	if grep -qs "ubuntu" /etc/os-release; then
		os="ubuntu"
		os_version=$(grep 'VERSION_ID' /etc/os-release | cut -d '"' -f 2 | tr -d '.')
		group_name="nogroup"
	elif [[ -e /etc/debian_version ]]; then
		os="debian"
		os_version=$(grep -oE '[0-9]+' /etc/debian_version | head -1)
		group_name="nogroup"
	elif [[ -e /etc/almalinux-release || -e /etc/rocky-release || -e /etc/centos-release ]]; then
		os="centos"
		os_version=$(grep -shoE '[0-9]+' /etc/almalinux-release /etc/rocky-release /etc/centos-release | head -1)
		group_name="nobody"
	elif [[ -e /etc/fedora-release ]]; then
		os="fedora"
		os_version=$(grep -oE '[0-9]+' /etc/fedora-release | head -1)
		group_name="nobody"
	else
		fatal_error "This installer seems to be running on an unsupported distribution. Supported distros are Ubuntu, Debian, AlmaLinux, Rocky Linux, CentOS and Fedora." $E_OS_UNSUPPORTED
	fi

	if [[ "$os" == "ubuntu" && "$os_version" -lt 2204 ]]; then
		fatal_error "Ubuntu 22.04 or higher is required to use this installer." $E_OS_UNSUPPORTED
	fi

	if [[ "$os" == "debian" ]]; then
		if grep -q '/sid' /etc/debian_version; then
			fatal_error "Debian Testing and Debian Unstable are unsupported by this installer." $E_OS_UNSUPPORTED
		fi
		if [[ "$os_version" -lt 11 ]]; then
			fatal_error "Debian 11 or higher is required to use this installer." $E_OS_UNSUPPORTED
		fi
	fi

	if [[ "$os" == "centos" && "$os_version" -lt 9 ]]; then
		os_name=$(sed 's/ release.*//' /etc/almalinux-release /etc/rocky-release /etc/centos-release 2>/dev/null | head -1)
		fatal_error "$os_name 9 or higher is required to use this installer." $E_OS_UNSUPPORTED
	fi

	if ! grep -q sbin <<< "$PATH"; then
		fatal_error '$PATH does not include sbin. Try using "su -" instead of "su".' $E_DEPENDENCY
	fi
}

install_openvpn() {
	# Detect some Debian minimal setups where neither wget nor curl are installed
	if ! hash wget 2>/dev/null && ! hash curl 2>/dev/null; then
		log_warn "Wget is required to use this installer."
		read -n1 -r -p "Press any key to install Wget and continue..."
		apt-get update
		apt-get install -y wget
	fi
	clear
	echo 'Welcome to this OpenVPN road warrior installer!'
	
	# IP Selection
	if [[ $(ip -4 addr | grep inet | grep -vEc '127(\.[0-9]{1,3}){3}') -eq 1 ]]; then
		ip=$(ip -4 addr | grep inet | grep -vE '127(\.[0-9]{1,3}){3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}')
	else
		number_of_ip=$(ip -4 addr | grep inet | grep -vEc '127(\.[0-9]{1,3}){3}')
		echo
		echo "Which IPv4 address should be used?"
		ip -4 addr | grep inet | grep -vE '127(\.[0-9]{1,3}){3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}' | nl -s ') '
		read -p "IPv4 address [1]: " ip_number
		until [[ -z "$ip_number" || "$ip_number" =~ ^[0-9]+$ && "$ip_number" -le "$number_of_ip" ]]; do
			echo "$ip_number: invalid selection."
			read -p "IPv4 address [1]: " ip_number
		done
		[[ -z "$ip_number" ]] && ip_number="1"
		ip=$(ip -4 addr | grep inet | grep -vE '127(\.[0-9]{1,3}){3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}' | sed -n "$ip_number"p)
	fi

	# NAT Check
	if echo "$ip" | grep -qE '^(10\.|172\.1[6789]\.|172\.2[0-9]\.|172\.3[01]\.|192\.168)'; then
		echo
		echo "This server is behind NAT. What is the public IPv4 address or hostname?"
		get_public_ip=$(grep -m 1 -oE '^[0-9]{1,3}(\.[0-9]{1,3}){3}$' <<< "$(wget -T 10 -t 1 -4qO- "http://ip1.dynupdate.no-ip.com/" || curl -m 10 -4Ls "http://ip1.dynupdate.no-ip.com/")")
		read -p "Public IPv4 address / hostname [$get_public_ip]: " public_ip
		until [[ -n "$get_public_ip" || -n "$public_ip" ]]; do
			echo "Invalid input."
			read -p "Public IPv4 address / hostname: " public_ip
		done
		[[ -z "$public_ip" ]] && public_ip="$get_public_ip"
		
		# Validate public IP if it looks like an IP
		if [[ "$public_ip" =~ ^[0-9]{1,3}(\.[0-9]{1,3}){3}$ ]]; then
			if ! validate_ip "$public_ip"; then
				log_warn "The entered IP address does not look valid, but proceeding."
			fi
		fi
	fi

	# IPv6 Setup
	if [[ $(ip -6 addr | grep -c 'inet6 [23]') -eq 1 ]]; then
		ip6=$(ip -6 addr | grep 'inet6 [23]' | cut -d '/' -f 1 | grep -oE '([0-9a-fA-F]{0,4}:){1,7}[0-9a-fA-F]{0,4}')
	fi
	if [[ $(ip -6 addr | grep -c 'inet6 [23]') -gt 1 ]]; then
		number_of_ip6=$(ip -6 addr | grep -c 'inet6 [23]')
		echo
		echo "Which IPv6 address should be used?"
		ip -6 addr | grep 'inet6 [23]' | cut -d '/' -f 1 | grep -oE '([0-9a-fA-F]{0,4}:){1,7}[0-9a-fA-F]{0,4}' | nl -s ') '
		read -p "IPv6 address [1]: " ip6_number
		until [[ -z "$ip6_number" || "$ip6_number" =~ ^[0-9]+$ && "$ip6_number" -le "$number_of_ip6" ]]; do
			echo "$ip6_number: invalid selection."
			read -p "IPv6 address [1]: " ip6_number
		done
		[[ -z "$ip6_number" ]] && ip6_number="1"
		ip6=$(ip -6 addr | grep 'inet6 [23]' | cut -d '/' -f 1 | grep -oE '([0-9a-fA-F]{0,4}:){1,7}[0-9a-fA-F]{0,4}' | sed -n "$ip6_number"p)
	fi

	# Protocol Selection
	echo
	echo "Which protocol should OpenVPN use?"
	echo "   1) UDP (recommended)"
	echo "   2) TCP"
	read -p "Protocol [1]: " protocol
	until [[ -z "$protocol" || "$protocol" =~ ^[12]$ ]]; do
		echo "$protocol: invalid selection."
		read -p "Protocol [1]: " protocol
	done
	case "$protocol" in
		1|"") protocol=udp ;;
		2) protocol=tcp ;;
	esac

	# Port Selection
	echo
	echo "What port should OpenVPN listen on?"
	read -p "Port [1194]: " port
	until [[ -z "$port" || "$port" =~ ^[0-9]+$ && "$port" -le 65535 ]]; do
		echo "$port: invalid port."
		read -p "Port [1194]: " port
	done
	[[ -z "$port" ]] && port="1194"

	# DNS Selection
	echo
	echo "Select a DNS server for the clients:"
	echo "   1) Default system resolvers"
	echo "   2) Google"
	echo "   3) 1.1.1.1"
	echo "   4) OpenDNS"
	echo "   5) Quad9"
	echo "   6) Gcore"
	echo "   7) AdGuard"
	echo "   8) Specify custom resolvers"
	read -p "DNS server [1]: " dns
	until [[ -z "$dns" || "$dns" =~ ^[1-8]$ ]]; do
		echo "$dns: invalid selection."
		read -p "DNS server [1]: " dns
	done

	if [[ "$dns" = "8" ]]; then
		echo
		until [[ -n "$custom_dns" ]]; do
			echo "Enter DNS servers (one or more IPv4 addresses, separated by commas or spaces):"
			read -p "DNS servers: " dns_input
			dns_input=$(echo "$dns_input" | tr ',' ' ')
			for dns_ip in $dns_input; do
				if validate_ip "$dns_ip"; then
					if [[ -z "$custom_dns" ]]; then
						custom_dns="$dns_ip"
					else
						custom_dns="$custom_dns $dns_ip"
					fi
				else
					log_warn "Skipping invalid DNS IP: $dns_ip"
				fi
			done
			if [ -z "$custom_dns" ]; then
				echo "Invalid input. Please enter at least one valid IPv4 address."
			fi
		done
	fi

	# Client Name
	echo
	echo "Enter a name for the first client:"
	read -p "Name [client]: " unsanitized_client
	client=$(sed 's/[^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-]/_/g' <<< "$unsanitized_client")
	[[ -z "$client" ]] && client="client"

	echo
	echo "OpenVPN installation is ready to begin."
	
	# Firewall Check
	if ! systemctl is-active --quiet firewalld.service && ! hash iptables 2>/dev/null; then
		if [[ "$os" == "centos" || "$os" == "fedora" ]]; then
			firewall="firewalld"
			echo "firewalld, which is required to manage routing tables, will also be installed."
		elif [[ "$os" == "debian" || "$os" == "ubuntu" ]]; then
			firewall="iptables"
		fi
	fi

	read -n1 -r -p "Press any key to continue..."
	log_info "Starting installation..."

	# Container Check
	if systemd-detect-virt -cq; then
		mkdir /etc/systemd/system/openvpn-server@server.service.d/ 2>/dev/null
		echo "[Service]
LimitNPROC=infinity" > /etc/systemd/system/openvpn-server@server.service.d/disable-limitnproc.conf
	fi

	# Install Dependencies
	log_info "Installing dependencies..."
	if [[ "$os" = "debian" || "$os" = "ubuntu" ]]; then
		apt-get update
		apt-get install -y --no-install-recommends openvpn openssl ca-certificates $firewall || fatal_error "Failed to install dependencies" $E_DEPENDENCY
	elif [[ "$os" = "centos" ]]; then
		dnf install -y epel-release
		dnf install -y openvpn openssl ca-certificates tar $firewall || fatal_error "Failed to install dependencies" $E_DEPENDENCY
	else
		dnf install -y openvpn openssl ca-certificates tar $firewall || fatal_error "Failed to install dependencies" $E_DEPENDENCY
	fi

	if [[ "$firewall" == "firewalld" ]]; then
		systemctl enable --now firewalld.service
	fi

	# Easy-RSA Setup
	log_info "Setting up Easy-RSA..."
	mkdir -p /etc/openvpn/server/easy-rsa/
	{ wget -qO- "$EASY_RSA_URL" 2>/dev/null || curl -sL "$EASY_RSA_URL" ; } | tar xz -C /etc/openvpn/server/easy-rsa/ --strip-components 1 || fatal_error "Failed to download Easy-RSA" $E_DEPENDENCY
	chown -R root:root /etc/openvpn/server/easy-rsa/
	cd /etc/openvpn/server/easy-rsa/ || fatal_error "Failed to change directory to Easy-RSA" $E_GENERAL

	# PKI Init
	./easyrsa --batch init-pki
	./easyrsa --batch build-ca nopass

	# DH Params
	log_info "Generating DH parameters..."
	echo '-----BEGIN DH PARAMETERS-----
MIIBCAKCAQEA//////////+t+FRYortKmq/cViAnPTzx2LnFg84tNpWp4TZBFGQz
+8yTnc4kmz75fS/jY2MMddj2gbICrsRhetPfHtXV/WVhJDP1H18GbtCFY2VVPe0a
87VXE15/V8k1mE8McODmi3fipona8+/och3xWKE2rec1MKzKT0g6eXq8CrGCsyT7
YdEIqUuyyOP7uWrat2DX9GgdT0Kj3jlN9K5W7edjcrsZCwenyO4KbXCeAvzhzffi
7MA0BM0oNC9hkXL+nOmFg/+OTxIy7vKBg8P+OxtMb61zO7X8vC7CIAXFjvGDfRaD
ssbzSibBsu/6iGtCOGEoXJf//////////wIBAg==
-----END DH PARAMETERS-----' > /etc/openvpn/server/dh.pem
	ln -s /etc/openvpn/server/dh.pem pki/dh.pem

	# Certificates
	log_info "Generating certificates..."
	./easyrsa --batch --days=3650 build-server-full server nopass
	./easyrsa --batch --days=3650 build-client-full "$client" nopass
	./easyrsa --batch --days=3650 gen-crl

	# Generate TLS-Crypt key
	log_info "Generating TLS-Crypt key..."
	openvpn --genkey secret /etc/openvpn/server/tc.key

	# Move Files
	cp pki/ca.crt pki/private/ca.key pki/issued/server.crt pki/private/server.key pki/crl.pem /etc/openvpn/server
	chown nobody:"$group_name" /etc/openvpn/server/crl.pem
	chmod o+x /etc/openvpn/server/

	# Server Config
	log_info "Creating server configuration..."
	echo "local $ip
port $port
proto $protocol
dev tun
ca ca.crt
cert server.crt
key server.key
dh dh.pem
auth SHA512
tls-crypt tc.key
topology subnet
server 10.8.0.0 255.255.255.0" > /etc/openvpn/server/server.conf

	if [[ -z "$ip6" ]]; then
		echo 'push "redirect-gateway def1 bypass-dhcp"' >> /etc/openvpn/server/server.conf
	else
		echo 'server-ipv6 fddd:1194:1194:1194::/64' >> /etc/openvpn/server/server.conf
		echo 'push "redirect-gateway def1 ipv6 bypass-dhcp"' >> /etc/openvpn/server/server.conf
	fi
	echo 'ifconfig-pool-persist ipp.txt' >> /etc/openvpn/server/server.conf

	# DNS Config
	case "$dns" in
		1|"")
			if grep '^nameserver' "/etc/resolv.conf" | grep -qv '127.0.0.53' ; then
				resolv_conf="/etc/resolv.conf"
			else
				resolv_conf="/run/systemd/resolve/resolv.conf"
			fi
			grep -v '^#\|^;' "$resolv_conf" | grep '^nameserver' | grep -v '127.0.0.53' | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}' | while read line; do
				echo "push \"dhcp-option DNS $line\"" >> /etc/openvpn/server/server.conf
			done
		;;
		2)
			echo 'push "dhcp-option DNS 8.8.8.8"' >> /etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 8.8.4.4"' >> /etc/openvpn/server/server.conf
		;;
		3)
			echo 'push "dhcp-option DNS 1.1.1.1"' >> /etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 1.0.0.1"' >> /etc/openvpn/server/server.conf
		;;
		4)
			echo 'push "dhcp-option DNS 208.67.222.222"' >> /etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 208.67.220.220"' >> /etc/openvpn/server/server.conf
		;;
		5)
			echo 'push "dhcp-option DNS 9.9.9.9"' >> /etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 149.112.112.112"' >> /etc/openvpn/server/server.conf
		;;
		6)
			echo 'push "dhcp-option DNS 95.85.95.85"' >> /etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 2.56.220.2"' >> /etc/openvpn/server/server.conf
		;;
		7)
			echo 'push "dhcp-option DNS 94.140.14.14"' >> /etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 94.140.15.15"' >> /etc/openvpn/server/server.conf
		;;
		8)
		for dns_ip in $custom_dns; do
			echo "push \"dhcp-option DNS $dns_ip\"" >> /etc/openvpn/server/server.conf
		done
		;;
	esac

	echo 'push "block-outside-dns"' >> /etc/openvpn/server/server.conf
	echo "keepalive 10 120
user nobody
group $group_name
persist-key
persist-tun
verb 3
crl-verify crl.pem" >> /etc/openvpn/server/server.conf
	if [[ "$protocol" = "udp" ]]; then
		echo "explicit-exit-notify" >> /etc/openvpn/server/server.conf
	fi

	# Systemctl & Firewall
	echo 'net.ipv4.ip_forward=1' > /etc/sysctl.d/99-openvpn-forward.conf
	echo 1 > /proc/sys/net/ipv4/ip_forward
	if [[ -n "$ip6" ]]; then
		echo "net.ipv6.conf.all.forwarding=1" >> /etc/sysctl.d/99-openvpn-forward.conf
		echo 1 > /proc/sys/net/ipv6/conf/all/forwarding
	fi

	if systemctl is-active --quiet firewalld.service; then
		firewall-cmd --add-port="$port"/"$protocol"
		firewall-cmd --zone=trusted --add-source=10.8.0.0/24
		firewall-cmd --permanent --add-port="$port"/"$protocol"
		firewall-cmd --permanent --zone=trusted --add-source=10.8.0.0/24
		firewall-cmd --direct --add-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to "$ip"
		firewall-cmd --permanent --direct --add-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to "$ip"
		if [[ -n "$ip6" ]]; then
			firewall-cmd --zone=trusted --add-source=fddd:1194:1194:1194::/64
			firewall-cmd --permanent --zone=trusted --add-source=fddd:1194:1194:1194::/64
			firewall-cmd --direct --add-rule ipv6 nat POSTROUTING 0 -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j SNAT --to "$ip6"
			firewall-cmd --permanent --direct --add-rule ipv6 nat POSTROUTING 0 -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j SNAT --to "$ip6"
		fi
	else
		iptables_path=$(command -v iptables)
		ip6tables_path=$(command -v ip6tables)
		if [[ $(systemd-detect-virt) == "openvz" ]] && readlink -f "$(command -v iptables)" | grep -q "nft" && hash iptables-legacy 2>/dev/null; then
			iptables_path=$(command -v iptables-legacy)
			ip6tables_path=$(command -v ip6tables-legacy)
		fi
		echo "[Unit]
After=network-online.target
Wants=network-online.target
[Service]
Type=oneshot
ExecStart=$iptables_path -w 5 -t nat -A POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to $ip
ExecStart=$iptables_path -w 5 -I INPUT -p $protocol --dport $port -j ACCEPT
ExecStart=$iptables_path -w 5 -I FORWARD -s 10.8.0.0/24 -j ACCEPT
ExecStart=$iptables_path -w 5 -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
ExecStop=$iptables_path -w 5 -t nat -D POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to $ip
ExecStop=$iptables_path -w 5 -D INPUT -p $protocol --dport $port -j ACCEPT
ExecStop=$iptables_path -w 5 -D FORWARD -s 10.8.0.0/24 -j ACCEPT
ExecStop=$iptables_path -w 5 -D FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT" > /etc/systemd/system/openvpn-iptables.service
		if [[ -n "$ip6" ]]; then
			echo "ExecStart=$ip6tables_path -w 5 -t nat -A POSTROUTING -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j SNAT --to $ip6
ExecStart=$ip6tables_path -w 5 -I FORWARD -s fddd:1194:1194:1194::/64 -j ACCEPT
ExecStart=$ip6tables_path -w 5 -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
ExecStop=$ip6tables_path -w 5 -t nat -D POSTROUTING -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j SNAT --to $ip6
ExecStop=$ip6tables_path -w 5 -D FORWARD -s fddd:1194:1194:1194::/64 -j ACCEPT
ExecStop=$ip6tables_path -w 5 -D FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT" >> /etc/systemd/system/openvpn-iptables.service
		fi
		echo "RemainAfterExit=yes
[Install]
WantedBy=multi-user.target" >> /etc/systemd/system/openvpn-iptables.service
		systemctl enable --now openvpn-iptables.service
	fi

	if sestatus 2>/dev/null | grep "Current mode" | grep -q "enforcing" && [[ "$port" != 1194 ]]; then
		if ! hash semanage 2>/dev/null; then
				dnf install -y policycoreutils-python-utils
		fi
		semanage port -a -t openvpn_port_t -p "$protocol" "$port"
	fi

	[[ -n "$public_ip" ]] && ip="$public_ip"
	
	echo "client
dev tun
proto $protocol
remote $ip $port
resolv-retry infinite
nobind
persist-key
persist-tun
remote-cert-tls server
auth SHA512
ignore-unknown-option block-outside-dns
verb 3" > /etc/openvpn/server/client-common.txt

	systemctl enable --now openvpn-server@server.service
	
	# Generate client config with tls-crypt key
	{
		grep -vh '^#' /etc/openvpn/server/client-common.txt /etc/openvpn/server/easy-rsa/pki/inline/private/"$client".inline
		echo "<tls-crypt>"
		cat /etc/openvpn/server/tc.key
		echo "</tls-crypt>"
	} > "$script_dir"/"$client".ovpn
	
	log_info "Finished!"
	echo
	echo "The client configuration is available in:" "$script_dir"/"$client.ovpn"
	echo "New clients can be added by running this script again."
}

add_client() {
	echo
	echo "Provide a name for the client:"
	read -p "Name: " unsanitized_client
	client=$(sed 's/[^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-]/_/g' <<< "$unsanitized_client")
	while [[ -z "$client" || -e /etc/openvpn/server/easy-rsa/pki/issued/"$client".crt ]]; do
		echo "$client: invalid name."
		read -p "Name: " unsanitized_client
		client=$(sed 's/[^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-]/_/g' <<< "$unsanitized_client")
	done
	cd /etc/openvpn/server/easy-rsa/ || fatal_error "Failed to change directory to Easy-RSA" $E_GENERAL
	./easyrsa --batch --days=3650 build-client-full "$client" nopass
	# Generate client config with tls-crypt key
	{
		grep -vh '^#' /etc/openvpn/server/client-common.txt /etc/openvpn/server/easy-rsa/pki/inline/private/"$client".inline
		echo "<tls-crypt>"
		cat /etc/openvpn/server/tc.key
		echo "</tls-crypt>"
	} > "$script_dir"/"$client".ovpn
	echo
	log_info "$client added. Configuration available in:" "$script_dir"/"$client.ovpn"
}

revoke_client() {
	number_of_clients=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -c "^V")
	if [[ "$number_of_clients" = 0 ]]; then
		echo
		echo "There are no existing clients!"
		exit $E_SUCCESS
	fi
	echo
	echo "Select the client to revoke:"
	tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | nl -s ') '
	read -p "Client: " client_number
	until [[ "$client_number" =~ ^[0-9]+$ && "$client_number" -le "$number_of_clients" ]]; do
		echo "$client_number: invalid selection."
		read -p "Client: " client_number
	done
	client=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | sed -n "$client_number"p)
	echo
	read -p "Confirm $client revocation? [y/N]: " revoke
	until [[ "$revoke" =~ ^[yYnN]*$ ]]; do
		echo "$revoke: invalid selection."
		read -p "Confirm $client revocation? [y/N]: " revoke
	done
	if [[ "$revoke" =~ ^[yY]$ ]]; then
		cd /etc/openvpn/server/easy-rsa/ || fatal_error "Failed to change directory to Easy-RSA" $E_GENERAL
		./easyrsa --batch revoke "$client"
		./easyrsa --batch --days=3650 gen-crl
		rm -f /etc/openvpn/server/crl.pem
		rm -f /etc/openvpn/server/easy-rsa/pki/reqs/"$client".req
		rm -f /etc/openvpn/server/easy-rsa/pki/private/"$client".key
		cp /etc/openvpn/server/easy-rsa/pki/crl.pem /etc/openvpn/server/crl.pem
		chown nobody:"$group_name" /etc/openvpn/server/crl.pem
		echo
		log_info "$client revoked!"
	else
		echo
		log_info "$client revocation aborted!"
	fi
}

remove_openvpn() {
	echo
	read -p "Confirm OpenVPN removal? [y/N]: " remove
	until [[ "$remove" =~ ^[yYnN]*$ ]]; do
		echo "$remove: invalid selection."
		read -p "Confirm OpenVPN removal? [y/N]: " remove
	done
	if [[ "$remove" =~ ^[yY]$ ]]; then
		# Backup before removal
		log_info "Backing up configuration..."
		backup_dir="/root/openvpn_backup_$(date +%Y%m%d_%H%M%S)"
		mkdir -p "$backup_dir"
		cp -r /etc/openvpn/server "$backup_dir" 2>/dev/null
		log_info "Backup saved to $backup_dir"

		port=$(grep '^port ' /etc/openvpn/server/server.conf | cut -d " " -f 2)
		protocol=$(grep '^proto ' /etc/openvpn/server/server.conf | cut -d " " -f 2)
		if systemctl is-active --quiet firewalld.service; then
			ip=$(firewall-cmd --direct --get-rules ipv4 nat POSTROUTING | grep '\-s 10.8.0.0/24 '"'"'!'"'"' -d 10.8.0.0/24' | grep -oE '[^ ]+$')
			firewall-cmd --remove-port="$port"/"$protocol"
			firewall-cmd --zone=trusted --remove-source=10.8.0.0/24
			firewall-cmd --permanent --remove-port="$port"/"$protocol"
			firewall-cmd --permanent --zone=trusted --remove-source=10.8.0.0/24
			firewall-cmd --direct --remove-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to "$ip"
			firewall-cmd --permanent --direct --remove-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to "$ip"
			if grep -qs "server-ipv6" /etc/openvpn/server/server.conf; then
				ip6=$(firewall-cmd --direct --get-rules ipv6 nat POSTROUTING | grep '\-s fddd:1194:1194:1194::/64 '"'"'!'"'"' -d fddd:1194:1194:1194::/64' | grep -oE '[^ ]+$')
				firewall-cmd --zone=trusted --remove-source=fddd:1194:1194:1194::/64
				firewall-cmd --permanent --zone=trusted --remove-source=fddd:1194:1194:1194::/64
				firewall-cmd --direct --remove-rule ipv6 nat POSTROUTING 0 -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j SNAT --to "$ip6"
				firewall-cmd --permanent --direct --remove-rule ipv6 nat POSTROUTING 0 -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j SNAT --to "$ip6"
			fi
		else
			systemctl disable --now openvpn-iptables.service
			rm -f /etc/systemd/system/openvpn-iptables.service
		fi
		if sestatus 2>/dev/null | grep "Current mode" | grep -q "enforcing" && [[ "$port" != 1194 ]]; then
			semanage port -d -t openvpn_port_t -p "$protocol" "$port"
		fi
		systemctl disable --now openvpn-server@server.service
		rm -f /etc/systemd/system/openvpn-server@server.service.d/disable-limitnproc.conf
		rm -f /etc/sysctl.d/99-openvpn-forward.conf
		if [[ "$os" = "debian" || "$os" = "ubuntu" ]]; then
			rm -rf /etc/openvpn/server
			apt-get remove --purge -y openvpn
		else
			dnf remove -y openvpn
			rm -rf /etc/openvpn/server
		fi
		echo
		log_info "OpenVPN removed!"
	else
		echo
		log_info "OpenVPN removal aborted!"
	fi
}

# --- Main Execution ---

# Store the absolute path of the directory where the script is located
script_dir="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"

initial_check

if [[ ! -e /etc/openvpn/server/server.conf ]]; then
	install_openvpn
else
	clear
	echo "OpenVPN is already installed."
	echo
	echo "Select an option:"
	echo "   1) Add a new client"
	echo "   2) Revoke an existing client"
	echo "   3) Remove OpenVPN"
	echo "   4) Exit"
	read -p "Option: " option
	until [[ "$option" =~ ^[1-4]$ ]]; do
		echo "$option: invalid selection."
		read -p "Option: " option
	done
	case "$option" in
		1) add_client ;;
		2) revoke_client ;;
		3) remove_openvpn ;;
		4) exit $E_SUCCESS ;;
	esac
fi