{
  config,
  pkgs,
  ...
}:
{
  imports = [
    ../../settings/services/caddy.nix
  ];
  age.secrets = {
    # TS_AUTHKEY for caddy-tailscale plugin
    caddy.file = ../../../secrets/caddy.age;
  };

  security.acme.defaults = {
    email = "security@${config.networking.domain}";
    dnsProvider = "pdns";
    validMinDays = 32;
  };

  services.tailscale.permitCertUid = config.services.caddy.user;
  services.caddy = {
    environmentFile = config.age.secrets.caddy.path;
    package = pkgs.caddy.withPlugins {
      plugins = [
        "github.com/caddyserver/cache-handler@v0.16.0"
        "github.com/tailscale/caddy-tailscale@v0.0.0-20260106222316-bb080c4414ac"
        "github.com/caddy-dns/rfc2136@v1.0.0"
        "pkg.jsn.cam/caddy-defender@v0.10.1"
        "github.com/mholt/caddy-ratelimit@v0.1.1-0.20260521172720-16aecbbcb8ca"
      ];
      hash = "sha256-qaHc2jmyFJ/MwazQpcdLe/fmEB13X1MtvfVBUR/MymA=";
    };
    globalConfig = ''
      cache
      tailscale {
        tags tag:app
      }
      acme_dns rfc2136 {
        key_name caddy
        key_alg hmac-sha512
        key "{env.DDNS_TSIG_KEY}"
        server pdns.alin.ovh:53
      }
    '';
    extraConfig = ''
      (rate_limit) {
        rate_limit {
          log_key
          zone global_static {
            match {
              query query=*
            }
            key static
            events 180
            window 1m
          }
          zone net_short {
            match {
              query query=*
            }
            key {remote_host}
            ipv4_prefix 24
            ipv6_prefix 56
            events 10
            window 5s
          }
        }
      }
      (defender) {
        defender ratelimit {
          ranges all
        }
        defender tarpit {
          tarpit_config {
            timeout 30s
            bytes_per_second 500
            response_code 200
          }
        }
      }
    '';
  };

  users.groups.caddy.members = [ "alin" ];
  users.groups.webservice = {
    members = [ "caddy" ];
  };
  systemd.tmpfiles.rules = [
    # setgid bit (2)
    # sticky bit (4)
    "d /run/web/ 6770 caddy webservice -"
  ];
  systemd.services.caddy.serviceConfig = {
    ReadWritePaths = [ "/run/web" ];
  };

  boot.kernel.sysctl =
    let
      buffer_size = 16 * 1024 * 1024;
      server_count = 2;
      max_clients = 100;
      page_size = 4096;
      # This server might have 100 clients simultaneously, so:
      #   max(tcp_wmem) * 2 * 100 / 4096
      mem = toString (buffer_size * server_count * max_clients / page_size);
    in
    {
      # Provide adequate buffer memory.
      # rmem_max and wmem_max are TCP max buffer size
      # settable with setsockopt(), in bytes
      # tcp_rmem and tcp_wmem are per socket in bytes.
      # tcp_mem is for all TCP streams, in 4096-byte pages.
      # The following are suggested on IBM's
      # High Performance Computing page
      "net.core.rmem_max" = buffer_size;
      "net.core.wmem_max" = buffer_size;
      "net.core.rmem_default" = buffer_size;
      "net.core.wmem_default" = buffer_size;
      "net.ipv4.tcp_rmem" = "4096 87380 ${toString buffer_size}";
      "net.ipv4.tcp_wmem" = "4096 87380 ${toString buffer_size}";
      "net.ipv4.tcp_mem" = "${mem} ${mem} ${mem}";

      "net.ipv4.tcp_sack" = 0;
      "net.ipv4.tcp_dsack" = 0;

      "net.ipv4.tcp_slow_start_after_idle" = 0;
    };

}