#!/usr/bin/env bash
# Enable Wake-on-LAN on the primary network interface of a Proxmox/Debian host
# Automates: https://i12bretro.github.io/tutorials/0608.html
# - Installs ethtool
# - Detects the primary network interface
# - Checks WOL support
# - Enables WOL and configures persistence via /etc/network/interfaces
# - Verifies configuration
# - Prints the MAC address and hostname

set -euo pipefail

# --- Helper functions --------------------------------------------------------

err() {
    echo "ERROR: $*" >&2
    exit 1
}

info() {
    echo "[*] $*"
}

# --- Preconditions -----------------------------------------------------------

if [[ $EUID -ne 0 ]]; then
    err "This script must be run as root (sudo)."
fi

if ! command -v ip >/dev/null 2>&1; then
    err "The 'ip' command is required but not found."
fi

# --- Install ethtool ---------------------------------------------------------

if ! command -v ethtool >/dev/null 2>&1; then
    info "Installing ethtool..."
    apt-get update -y >/dev/null
    apt-get install -y ethtool >/dev/null
else
    info "ethtool already installed."
fi

# --- Detect primary network interface ----------------------------------------

# 1) Try to get interface from default route
PRIMARY_IF=$(ip route 2>/dev/null | awk '/default/ {print $5; exit}')

# 2) Fallback: first interface with a private IPv4 address
if [[ -z "${PRIMARY_IF:-}" ]]; then
    PRIMARY_IF=$(ip -o -4 addr show scope global | \
        awk '
            {
                split($4, a, "/");
                ip = a[1];
                if (ip ~ /^10\./ ||
                    ip ~ /^192\.168\./ ||
                    ip ~ /^172\.(1[6-9]|2[0-9]|3[0-1])\./) {
                    print $2;
                    exit;
                }
            }')
fi

[[ -n "${PRIMARY_IF:-}" ]] || err "Could not automatically determine primary network interface."

info "Detected primary interface: ${PRIMARY_IF}"

# --- Get MAC address & IP ----------------------------------------------------

MAC_ADDR=$(ip -o link show "$PRIMARY_IF" | awk '{for (i=1; i<=NF; i++) if ($i=="link/ether") print $(i+1)}')
IP_ADDR=$(ip -o -4 addr show "$PRIMARY_IF" | awk '{print $4}')

[[ -n "${MAC_ADDR:-}" ]] || err "Could not determine MAC address for interface ${PRIMARY_IF}."
[[ -n "${IP_ADDR:-}" ]] || info "No IPv4 address detected on ${PRIMARY_IF} (continuing anyway)."

info "Interface ${PRIMARY_IF} MAC: ${MAC_ADDR}"
[[ -n "${IP_ADDR:-}" ]] && info "Interface ${PRIMARY_IF} IP: ${IP_ADDR}"

# --- Check WOL support -------------------------------------------------------

info "Checking WOL support on ${PRIMARY_IF}..."

ETHTOOL_OUTPUT=$(ethtool "$PRIMARY_IF" 2>/dev/null || true)
[[ -n "$ETHTOOL_OUTPUT" ]] || err "ethtool failed on ${PRIMARY_IF}. Does this interface exist and support ethtool?"

SUPPORTS_WOL=$(awk -F: '/Supports Wake-on/ {gsub(/ /,"",$2); print $2}' <<<"$ETHTOOL_OUTPUT")

if [[ "$SUPPORTS_WOL" != *g* ]]; then
    err "Interface ${PRIMARY_IF} does NOT support Wake-on: g (Supports Wake-on: ${SUPPORTS_WOL}). Aborting."
fi

info "Interface ${PRIMARY_IF} supports Wake-on: g."

# --- Enable WOL immediately --------------------------------------------------

info "Enabling WOL (g) on ${PRIMARY_IF} now..."
ethtool -s "$PRIMARY_IF" wol g

# --- Configure persistence in /etc/network/interfaces ------------------------

INTERFACES_FILE="/etc/network/interfaces"

if [[ ! -f "$INTERFACES_FILE" ]]; then
    err "${INTERFACES_FILE} not found. Your system may be using another network config method (e.g., systemd-networkd, Netplan)."
fi

# Backup the file
BACKUP_FILE="${INTERFACES_FILE}.bak-$(date +%F-%H%M%S)"
cp "$INTERFACES_FILE" "$BACKUP_FILE"
info "Backed up ${INTERFACES_FILE} to ${BACKUP_FILE}"

# If an ethernet-wol or ethtool post-up line already exists for this interface, don't duplicate
if grep -Eq "ethernet-wol g" "$INTERFACES_FILE" || \
   grep -Eq "ethtool -s ${PRIMARY_IF} wol g" "$INTERFACES_FILE"; then
    info "WOL persistence settings already present in ${INTERFACES_FILE}; not adding again."
else
    info "Adding 'ethernet-wol g' under iface ${PRIMARY_IF} in ${INTERFACES_FILE}..."

    # Check if iface stanza exists
    if grep -Eq "^iface[[:space:]]+${PRIMARY_IF}[[:space:]]" "$INTERFACES_FILE"; then
        # Insert 'ethernet-wol g' directly after the iface line for this interface
        awk -v iface="$PRIMARY_IF" '
            {
                print $0
                if ($1 == "iface" && $2 == iface && !seen) {
                    print "    ethernet-wol g"
                    seen = 1
                }
            }
        ' "$INTERFACES_FILE" > "${INTERFACES_FILE}.tmp"

        mv "${INTERFACES_FILE}.tmp" "$INTERFACES_FILE"
        info "Updated ${INTERFACES_FILE} to include ethernet-wol g for ${PRIMARY_IF}."
    else
        info "No iface stanza for ${PRIMARY_IF} found in ${INTERFACES_FILE}."
        info "Not modifying the file to avoid breaking your network configuration."
        info "You may need to manually add 'ethernet-wol g' to the appropriate iface section."
    fi
fi

# --- Verify WOL is enabled ---------------------------------------------------

info "Verifying WOL is enabled on ${PRIMARY_IF}..."

VERIFY_OUTPUT=$(ethtool "$PRIMARY_IF")
WAKE_ON=$(awk -F: '/Wake-on/ {gsub(/ /,"",$2); print $2}' <<<"$VERIFY_OUTPUT")

if [[ "$WAKE_ON" != "g" ]]; then
    err "WOL verification failed: Wake-on is '${WAKE_ON}', expected 'g'. Check BIOS settings and /etc/network/interfaces."
fi

info "WOL verification succeeded: Wake-on is '${WAKE_ON}'."

# --- Final summary -----------------------------------------------------------

HOSTNAME=$(hostname)

echo
echo "==========================================="
echo " Wake-on-LAN Configuration Summary"
echo "==========================================="
echo " Hostname   : ${HOSTNAME}"
echo " Interface  : ${PRIMARY_IF}"
echo " MAC        : ${MAC_ADDR}"
[[ -n "${IP_ADDR:-}" ]] && echo " IP         : ${IP_ADDR}"
echo " Wake-on    : ${WAKE_ON}"
echo "==========================================="
echo "NOTE: Make sure WOL is enabled in your system BIOS/UEFI."
echo

exit 0