#!/usr/bin/env bash

set -euo pipefail

# Linux Static IP Configurator
# Supports:
#   - NetworkManager (nmcli)
#   - Netplan
#
# Run as root:
#   sudo ./set-static-ip.sh

if [[ "${EUID}" -ne 0 ]]; then
    echo "Dieses Script muss als root ausgeführt werden."
    echo "Bitte nutze: sudo $0"
    exit 1
fi

command_exists() {
    command -v "$1" >/dev/null 2>&1
}

pause() {
    echo
    read -r -p "Drücke Enter, um fortzufahren..."
}

get_interfaces() {
    ip -o link show | awk -F': ' '{print $2}' | grep -v '^lo$'
}

select_interface() {
    echo "Verfügbare Netzwerkinterfaces:"
    echo

    mapfile -t interfaces < <(get_interfaces)

    if [[ "${#interfaces[@]}" -eq 0 ]]; then
        echo "Keine Netzwerkinterfaces gefunden."
        exit 1
    fi

    for i in "${!interfaces[@]}"; do
        state=$(cat "/sys/class/net/${interfaces[$i]}/operstate" 2>/dev/null || echo "unknown")
        echo "  $((i + 1))) ${interfaces[$i]} [$state]"
    done

    echo
    while true; do
        read -r -p "Interface auswählen [1-${#interfaces[@]}]: " choice

        if [[ "$choice" =~ ^[0-9]+$ ]] &&
           (( choice >= 1 && choice <= ${#interfaces[@]} )); then
            INTERFACE="${interfaces[$((choice - 1))]}"
            break
        fi

        echo "Ungültige Auswahl."
    done
}

validate_ipv4() {
    local ip="$1"
    local IFS=.
    local -a octets

    read -ra octets <<< "$ip"

    [[ "${#octets[@]}" -eq 4 ]] || return 1

    for octet in "${octets[@]}"; do
        [[ "$octet" =~ ^[0-9]+$ ]] || return 1
        (( octet >= 0 && octet <= 255 )) || return 1
    done

    return 0
}

validate_cidr() {
    local cidr="$1"
    [[ "$cidr" =~ ^[0-9]+$ ]] && (( cidr >= 0 && cidr <= 32 ))
}

ask_network_data() {
    echo
    echo "Statische IPv4-Konfiguration"
    echo "----------------------------"

    while true; do
        read -r -p "IPv4-Adresse (z.B. 192.168.1.50): " IP_ADDRESS
        validate_ipv4 "$IP_ADDRESS" && break
        echo "Ungültige IPv4-Adresse."
    done

    while true; do
        read -r -p "CIDR-Präfix (z.B. 24): " PREFIX
        validate_cidr "$PREFIX" && break
        echo "Ungültiges CIDR-Präfix."
    done

    while true; do
        read -r -p "Gateway (z.B. 192.168.1.1): " GATEWAY
        validate_ipv4 "$GATEWAY" && break
        echo "Ungültiges Gateway."
    done

    read -r -p "DNS-Server, mit Leerzeichen getrennt [1.1.1.1 8.8.8.8]: " DNS_INPUT
    DNS_INPUT="${DNS_INPUT:-1.1.1.1 8.8.8.8}"

    DNS_SERVERS=()
    for dns in $DNS_INPUT; do
        if ! validate_ipv4 "$dns"; then
            echo "Ungültiger DNS-Server: $dns"
            exit 1
        fi
        DNS_SERVERS+=("$dns")
    done

    echo
    echo "Gewählte Konfiguration:"
    echo "  Interface : $INTERFACE"
    echo "  IP-Adresse: $IP_ADDRESS/$PREFIX"
    echo "  Gateway   : $GATEWAY"
    echo "  DNS       : ${DNS_SERVERS[*]}"
    echo

    read -r -p "Konfiguration anwenden? [j/N]: " confirm
    case "${confirm,,}" in
        j|ja|y|yes)
            ;;
        *)
            echo "Abgebrochen."
            exit 0
            ;;
    esac
}

configure_networkmanager() {
    echo
    echo "NetworkManager erkannt."

    local connection
    connection=$(nmcli -t -f NAME,DEVICE connection show --active \
        | awk -F: -v iface="$INTERFACE" '$2 == iface {print $1; exit}')

    if [[ -z "$connection" ]]; then
        connection=$(nmcli -t -f NAME,DEVICE connection show \
            | awk -F: -v iface="$INTERFACE" '$2 == iface {print $1; exit}')
    fi

    if [[ -z "$connection" ]]; then
        connection="static-$INTERFACE"
        echo "Keine bestehende Verbindung gefunden."
        echo "Erstelle NetworkManager-Verbindung: $connection"

        nmcli connection add \
            type ethernet \
            ifname "$INTERFACE" \
            con-name "$connection"
    else
        echo "Verwende Verbindung: $connection"
    fi

    local backup_dir="/root/network-backup-$(date +%Y%m%d-%H%M%S)"
    mkdir -p "$backup_dir"

    if [[ -d /etc/NetworkManager/system-connections ]]; then
        cp -a /etc/NetworkManager/system-connections "$backup_dir/" 2>/dev/null || true
    fi

    echo "Backup: $backup_dir"

    local dns_csv
    dns_csv=$(IFS=,; echo "${DNS_SERVERS[*]}")

    nmcli connection modify "$connection" \
        ipv4.method manual \
        ipv4.addresses "$IP_ADDRESS/$PREFIX" \
        ipv4.gateway "$GATEWAY" \
        ipv4.dns "$dns_csv" \
        ipv4.ignore-auto-dns yes

    nmcli connection up "$connection"

    echo
    echo "Statische IP wurde mit NetworkManager gesetzt."
}

configure_netplan() {
    echo
    echo "Netplan erkannt."

    local backup_dir="/root/netplan-backup-$(date +%Y%m%d-%H%M%S)"
    mkdir -p "$backup_dir"
    cp -a /etc/netplan/. "$backup_dir/" 2>/dev/null || true

    echo "Backup: $backup_dir"

    local config_file="/etc/netplan/99-static-ip.yaml"
    local dns_yaml=""

    for dns in "${DNS_SERVERS[@]}"; do
        if [[ -n "$dns_yaml" ]]; then
            dns_yaml+=", "
        fi
        dns_yaml+="$dns"
    done

    cat > "$config_file" <<EOF
network:
  version: 2
  ethernets:
    $INTERFACE:
      dhcp4: false
      addresses:
        - $IP_ADDRESS/$PREFIX
      routes:
        - to: default
          via: $GATEWAY
      nameservers:
        addresses: [$dns_yaml]
EOF

    chmod 600 "$config_file"

    echo
    echo "Netplan-Datei erstellt:"
    echo "  $config_file"
    echo
    echo "Teste die Konfiguration..."

    if command_exists netplan; then
        netplan generate

        echo
        echo "WICHTIG:"
        echo "Bei einer SSH-Verbindung kann die Verbindung nach dem Anwenden abbrechen."
        echo

        netplan apply
    else
        echo "Fehler: netplan-Befehl wurde nicht gefunden."
        exit 1
    fi

    echo
    echo "Statische IP wurde mit Netplan gesetzt."
}

show_result() {
    echo
    echo "Aktuelle Adressen auf $INTERFACE:"
    ip -4 addr show dev "$INTERFACE" || true

    echo
    echo "Routing:"
    ip route || true

    echo
    echo "Fertig."
}

clear

echo "====================================="
echo " Linux Static IP Configurator"
echo "====================================="
echo

select_interface
ask_network_data

if command_exists nmcli && nmcli general status >/dev/null 2>&1; then
    configure_networkmanager
elif [[ -d /etc/netplan ]] && compgen -G "/etc/netplan/*.yaml" >/dev/null; then
    configure_netplan
elif [[ -d /etc/netplan ]] && command_exists netplan; then
    configure_netplan
else
    echo
    echo "Kein unterstütztes Netzwerk-Backend erkannt."
    echo
    echo "Unterstützt werden:"
    echo "  - NetworkManager / nmcli"
    echo "  - Netplan"
    echo
    echo "Bei Debian mit /etc/network/interfaces ist eine manuelle"
    echo "Konfiguration erforderlich."
    exit 1
fi

show_result