#!/usr/bin/bash
set -euo pipefail

container_name="ts-lan-telemt"
output_dir="/var/lib/zabbix"
json_target="${output_dir}/telemt-active-ips.json"
text_target="${output_dir}/telemt-active-ips.txt"
metrics_target="${output_dir}/telemt-metrics.prom"

install -d -o root -g zabbix -m 0750 "${output_dir}"

container_pid="$(docker inspect --format '{{.State.Pid}}' "${container_name}")"
if [[ -z "${container_pid}" || "${container_pid}" == "0" ]]; then
  exit 1
fi

host_ip="$(ip -4 route get 1.1.1.1 | awk '{for (i=1; i<=NF; i++) if ($i == "src") {print $(i+1); exit}}')"
if [[ -z "${host_ip}" ]]; then
  exit 1
fi

json_tmp="$(mktemp "${output_dir}/.telemt-active-ips.json.XXXXXX")"
text_tmp="$(mktemp "${output_dir}/.telemt-active-ips.txt.XXXXXX")"
metrics_tmp="$(mktemp "${output_dir}/.telemt-metrics.prom.XXXXXX")"
trap 'rm -f "${json_tmp}" "${text_tmp}" "${metrics_tmp}"' EXIT

# The API response also contains proxy links and secrets. Filter it in-memory
# and persist only the username and current active IP address list.
nsenter -t "${container_pid}" -n \
  curl --fail --silent --show-error --max-time 5 \
  http://127.0.0.1:9091/v1/users |
  jq --compact-output '{
    users: [
      .data[]
      | {
          username,
          active_unique_ips: (.active_unique_ips_list // [])
        }
    ]
  }' > "${json_tmp}"

{
  active_count="$(jq '[.users[].active_unique_ips[]] | unique | length' "${json_tmp}")"
  printf 'Active IP addresses: %s\n' "${active_count}"
  jq --raw-output '
    [
      .users[] as $user
      | $user.active_unique_ips[]
      | "\($user.username) | \(.)"
    ]
    | if length == 0 then ["No active IP addresses"] else . end
    | .[]
  ' "${json_tmp}"
} > "${text_tmp}"

# Cache Prometheus output locally. Zabbix active checks read the cache, so the
# central server does not need a route to each private Docker host.
curl --fail --silent --show-error --max-time 5 \
  "http://${host_ip}:9092/metrics" > "${metrics_tmp}"

chown root:zabbix "${json_tmp}" "${text_tmp}" "${metrics_tmp}"
chmod 0640 "${json_tmp}" "${text_tmp}" "${metrics_tmp}"
mv -f "${json_tmp}" "${json_target}"
mv -f "${text_tmp}" "${text_target}"
mv -f "${metrics_tmp}" "${metrics_target}"