#!/bin/bash
# Toggle Pi-hole DNS on/off for active network connection

set -e

# Pi-hole DNS servers on the Raspberry Pi pair, with the router as last-resort fallback.
PIHOLE_DNS="192.168.1.127 192.168.1.128 192.168.1.101 192.168.1.1"

# Colors for output
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
RED='\033[0;31m'
NC='\033[0m' # No Color

# Get active Ethernet/Wi-Fi connection names.
get_active_connections() {
    nmcli -t -f NAME,DEVICE,TYPE connection show --active | \
        awk -F: '$2 != "lo" && ($3 == "802-3-ethernet" || $3 == "802-11-wireless") { print $1 }'
}

# Check if Pi-hole DNS is currently enabled
is_pihole_enabled() {
    local connection="$1"
    local ignore_auto_dns
    local configured_dns

    ignore_auto_dns=$(nmcli -g ipv4.ignore-auto-dns connection show "$connection")
    configured_dns=$(nmcli -g ipv4.dns connection show "$connection" | tr ',' ' ')

    [[ "$ignore_auto_dns" == "yes" && "$configured_dns" == "$PIHOLE_DNS" ]]
}

# Enable Pi-hole DNS
enable_pihole() {
    local connection

    for connection in "$@"; do
        echo -e "${YELLOW}Enabling Pi-hole DNS for connection: $connection${NC}"
        nmcli con mod "$connection" ipv4.dns "$PIHOLE_DNS"
        nmcli con mod "$connection" ipv4.ignore-auto-dns yes
        nmcli con up "$connection" > /dev/null 2>&1
    done

    echo -e "${GREEN}✓ Pi-hole DNS enabled${NC}"
    echo "DNS servers: $PIHOLE_DNS"
}

# Disable Pi-hole DNS (use DHCP-provided DNS)
disable_pihole() {
    local connection

    for connection in "$@"; do
        echo -e "${YELLOW}Disabling Pi-hole DNS for connection: $connection${NC}"
        nmcli con mod "$connection" ipv4.dns ""
        nmcli con mod "$connection" ipv4.ignore-auto-dns no
        nmcli con up "$connection" > /dev/null 2>&1
    done

    echo -e "${GREEN}✓ Pi-hole DNS disabled (using DHCP DNS)${NC}"
}

all_connections_pihole_enabled() {
    local connection

    for connection in "$@"; do
        if ! is_pihole_enabled "$connection"; then
            return 1
        fi
    done

    return 0
}

# Show current DNS status
show_status() {
    echo -e "\n${YELLOW}Current DNS configuration:${NC}"
    nmcli dev show | awk -F: '
        function trim(value) {
            sub(/^[[:space:]]+/, "", value)
            sub(/[[:space:]]+$/, "", value)
            return value
        }
        /^GENERAL.DEVICE:/ { device=trim($2) }
        /^IP4.DNS/ { print device ": " trim($2) }
    '
}

# Check if running on Fedora
check_os() {
    if [[ ! -f /etc/fedora-release ]]; then
        echo -e "${RED}Error: This script is designed for Fedora Linux only${NC}"
        if [[ -f /etc/os-release ]]; then
            source /etc/os-release
            echo "Detected OS: $NAME"
        fi
        exit 1
    fi
}

# Main logic
main() {
    # Check OS compatibility
    check_os

    # Check if running as root
    if [[ $EUID -eq 0 ]]; then
        echo -e "${RED}Error: Do not run this script as root${NC}"
        exit 1
    fi

    # Get active connections
    mapfile -t CONNECTIONS < <(get_active_connections)
    
    if [[ "${#CONNECTIONS[@]}" -eq 0 ]]; then
        echo -e "${RED}Error: No active network connection found${NC}"
        exit 1
    fi

    echo "Active connections: ${CONNECTIONS[*]}"

    # Handle command-line arguments
    case "${1:-toggle}" in
        on|enable)
            enable_pihole "${CONNECTIONS[@]}"
            show_status
            ;;
        off|disable)
            disable_pihole "${CONNECTIONS[@]}"
            show_status
            ;;
        status)
            if all_connections_pihole_enabled "${CONNECTIONS[@]}"; then
                echo -e "${GREEN}Pi-hole DNS is currently ENABLED${NC}"
            else
                echo -e "${YELLOW}Pi-hole DNS is currently DISABLED${NC}"
            fi
            show_status
            ;;
        toggle|*)
            if all_connections_pihole_enabled "${CONNECTIONS[@]}"; then
                disable_pihole "${CONNECTIONS[@]}"
            else
                enable_pihole "${CONNECTIONS[@]}"
            fi
            show_status
            ;;
    esac
}

main "$@"