#!/bin/bash

set -uo pipefail

textfile_dir={{ node_exporter_textfile_dir }}
file=${textfile_dir}/wireguard.prom
tmp=${file}.$$
now=$(date +%s)

mkdir -p ${textfile_dir}

peer_name() {
    case "$1" in
{% for key, name in wireguard_peer_names.items() %}
        "{{ key }}") echo "{{ name }}" ;;
{% endfor %}
        *) echo "unknown" ;;
    esac
}

{
    echo "# HELP wireguard_peer_last_handshake_seconds Unix time of the last handshake with a peer."
    echo "# TYPE wireguard_peer_last_handshake_seconds gauge"
    echo "# HELP wireguard_peer_handshake_age_seconds Seconds since the last handshake with a peer."
    echo "# TYPE wireguard_peer_handshake_age_seconds gauge"
    echo "# HELP wireguard_peer_up Whether a peer handshaked within the last five minutes."
    echo "# TYPE wireguard_peer_up gauge"
    echo "# HELP wireguard_peer_receive_bytes_total Bytes received from a peer."
    echo "# TYPE wireguard_peer_receive_bytes_total counter"
    echo "# HELP wireguard_peer_transmit_bytes_total Bytes sent to a peer."
    echo "# TYPE wireguard_peer_transmit_bytes_total counter"

    wg show all dump 2>/dev/null | awk 'NF >= 8' | while read -r interface key psk endpoint allowed handshake rx tx keepalive
    do
        name=$(peer_name "${key}")
        labels="interface=\"${interface}\",peer=\"${name}\""

        age=$((now - handshake))
        up=0

        if [ "${handshake}" -gt 0 ] && [ "${age}" -lt 300 ]
        then
            up=1
        fi

        if [ "${handshake}" -eq 0 ]
        then
            age=-1
        fi

        echo "wireguard_peer_last_handshake_seconds{${labels}} ${handshake}"
        echo "wireguard_peer_handshake_age_seconds{${labels}} ${age}"
        echo "wireguard_peer_up{${labels}} ${up}"
        echo "wireguard_peer_receive_bytes_total{${labels}} ${rx}"
        echo "wireguard_peer_transmit_bytes_total{${labels}} ${tx}"
    done
} > "${tmp}"

chmod 0644 "${tmp}"
mv "${tmp}" "${file}"