{ config, lib, pkgs, ... }:
{
  systemd = {
    timers = {
      tgbot-send = {
        wantedBy = [ "timers.target" ];
        timerConfig = {
          OnCalendar = "*-*-01 16:00:00";
          Persistent = true;
        };
      };
      network-watchdog = {
        wantedBy = [ "timers.target" ];
        timerConfig = {
          OnBootSec = 30;
          AccuracySec = 1;
          OnUnitActiveSec = 10;
        };
      };
    };
    services = {
      tgbot-send = {
        serviceConfig.Type = "oneshot";
        script = ''
          . /secrets/tgbot.env
          for msg in "''${MESSAGES[@]}"; do
            TEXT="''${msg#*:}"
            CHAT_ID="''${msg%%:*}"
            ${pkgs.curl}/bin/curl -X POST "https://api.telegram.org/$BOT/sendMessage" \
              -d "chat_id=$CHAT_ID" -d "text=$TEXT" 2> /dev/null | ${pkgs.jq}/bin/jq
            sleep 1
          done
        '';
      };
      network-watchdog = {
        serviceConfig = {
          Type = "oneshot";
          LogLevelMax = "notice";
        };
        script = ''
          if [ ! -e /run/network.failures ] || [ ! -e /run/network.limit ] || \
            ${pkgs.curl}/bin/curl --head --max-time 3 https://www.google.com; then
            limit=3
            failures=0
          else
            limit=$(cat /run/network.limit)
            failures=$((1+$(cat /run/network.failures)))
            [ $failures -gt 1 ] && echo "<5>failures = $failures"
          fi
          if [ $failures -ge $limit ]; then
            echo "<4>restarting NetworkManager"
            systemctl restart NetworkManager.service
            [ $limit -lt 60 ] && limit=$((4*$limit/3))
            failures=0
          fi
          echo $limit > /run/network.limit
          echo $failures > /run/network.failures
        '';
      };
    };
  };
}