#!/bin/bash
#
# Interactive Static IP Configuration Script using nmcli
# Usage: sudo bash set_static_ip_nmcli.sh
#

set -euo pipefail

log() { echo "[$(date '+%Y-%m-%d %H:%M:%S')] $*"; }

if [ "$(id -u)" -ne 0 ]; then
    log "ERROR: This script must be run as root (use sudo)."
    exit 1
fi

if ! command -v nmcli &> /dev/null; then
    log "ERROR: nmcli is not installed. This system may not be using NetworkManager."
    exit 1
fi

echo "========================================="
echo "   NetworkManager Static IP Setup"
echo "========================================="
echo ""
log "Available Network Connections:"
mapfile -t CONNECTIONS < <(nmcli -t -f NAME connection show)

if [ ${#CONNECTIONS[@]} -eq 0 ]; then
    log "ERROR: No network connections found."
    exit 1
fi

for i in "${!CONNECTIONS[@]}"; do
    echo "  $((i+1)). ${CONNECTIONS[$i]}"
done
echo ""

read -p "Enter the number of the connection to configure: " CONN_CHOICE
if ! [[ "$CONN_CHOICE" =~ ^[0-9]+$ ]] || [ "$CONN_CHOICE" -lt 1 ] || [ "$CONN_CHOICE" -gt "${#CONNECTIONS[@]}" ]; then
    log "ERROR: Invalid selection. Please enter a valid number from the list."
    exit 1
fi

CONN_NAME="${CONNECTIONS[$((CONN_CHOICE-1))]}"

echo ""
log "Current settings for '$CONN_NAME':"
CUR_METHOD=$(nmcli -g ipv4.method connection show "$CONN_NAME")
CUR_IP=$(nmcli -g IP4.ADDRESS connection show "$CONN_NAME")
if [ -z "$CUR_IP" ]; then
    CUR_IP=$(nmcli -g ipv4.addresses connection show "$CONN_NAME")
fi
CUR_GW=$(nmcli -g ipv4.gateway connection show "$CONN_NAME")
CUR_DNS=$(nmcli -g ipv4.dns connection show "$CONN_NAME")
echo "  - Method:  ${CUR_METHOD:-<Not Set>}"
echo "  - IP Addr (CIDR): ${CUR_IP:-<Not Set>}"
echo "  - Gateway: ${CUR_GW:-<Not Set>}"
echo "  - DNS:     ${CUR_DNS:-<Not Set>}"
echo ""

IPV4_CIDR_REGEX="^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/([0-9]|[1-2][0-9]|3[0-2])$"
IPV4_REGEX="^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$"
DNS_REGEX="^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)(,[ ]?((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))*$"

read -p "Enter static IP address with CIDR (e.g., 192.168.1.100/24): " IP_ADDR
if [ -z "$IP_ADDR" ]; then
    log "ERROR: IP address cannot be empty."
    exit 1
fi

if ! [[ "$IP_ADDR" =~ $IPV4_CIDR_REGEX ]]; then
    log "ERROR: Invalid IP address format. Must be a valid IPv4 CIDR notation (e.g., 192.168.1.100/24)."
    exit 1
fi

read -p "Enter Gateway IP address (e.g., 192.168.1.1): " GATEWAY
if [ -z "$GATEWAY" ]; then
    log "ERROR: Gateway cannot be empty."
    exit 1
fi
if ! [[ "$GATEWAY" =~ $IPV4_REGEX ]]; then
    log "ERROR: Invalid Gateway IP format (e.g., 192.168.1.1)."
    exit 1
fi

read -p "Enter DNS server(s) separated by commas (e.g., 8.8.8.8,1.1.1.1): " DNS_SERVERS
if [ -z "$DNS_SERVERS" ]; then
    log "ERROR: DNS servers cannot be empty."
    exit 1
fi
if ! [[ "$DNS_SERVERS" =~ $DNS_REGEX ]]; then
    log "ERROR: Invalid DNS server format. Must be comma-separated IPv4 addresses (e.g., 8.8.8.8,1.1.1.1)."
    exit 1
fi

log "Applying static IP configuration to '$CONN_NAME'..."
nmcli connection modify "$CONN_NAME" ipv4.method manual ipv4.addresses "$IP_ADDR" ipv4.gateway "$GATEWAY" ipv4.dns "$DNS_SERVERS"

log "Restarting connection to apply changes (you may lose SSH briefly if connected remotely)..."
nmcli connection up "$CONN_NAME"

log "=== Configuration Complete ==="
log "Verify your new IP address using 'ip addr show' or 'nmcli device show'."