{
  config,
  lib,
  vhackPackages,
  ...
}: let
  cfg = config.vhack.back;

  mkUnit = repoPath: port: {
    description = "Back service for ${repoPath}";
    wants = ["network-online.target"];
    after = ["network-online.target"];
    wantedBy = ["default.target"];

    environment = {
      ROCKET_PORT = builtins.toString port;
      BACK_SOURCE_CODE_REPOSITORY_URL = "https://git.vhack.eu/vhack.eu/nixos-server/tree/pkgs/by-name/ba/back";
    };

    serviceConfig = {
      ExecStart = "${lib.getExe vhackPackages.back} ${lib.strings.escapeShellArg repoPath}";

      # Ensure that the service can read the repository
      # FIXME(@bpeetz): This has the implied assumption, that all the exposed git
      # repositories are readable for the git group. This should not be necessary. <2024-12-23>
      User = "git";
      Group = "git";

      DynamicUser = true;
      Restart = "always";

      # Sandboxing
      ProtectSystem = "strict";
      ProtectHome = true;
      PrivateTmp = true;
      PrivateDevices = true;
      ProtectHostname = true;
      ProtectClock = true;
      ProtectKernelTunables = true;
      ProtectKernelModules = true;
      ProtectKernelLogs = true;
      ProtectControlGroups = true;
      RestrictAddressFamilies = ["AF_UNIX" "AF_INET" "AF_INET6"];
      RestrictNamespaces = true;
      LockPersonality = true;
      MemoryDenyWriteExecute = true;
      RestrictRealtime = true;
      RestrictSUIDSGID = true;
      RemoveIPC = true;
      PrivateMounts = true;
      # System Call Filtering
      SystemCallArchitectures = "native";
      SystemCallFilter = ["~@cpu-emulation @debug @keyring @mount @obsolete @privileged @setuid"];
    };
  };

  mkVirtalHost = port: {
    locations."/".proxyPass = "http://127.0.0.1:${builtins.toString port}";

    enableACME = true;
    forceSSL = true;
  };

  services =
    lib.mapAttrs' (gitPath: config: {
      name = builtins.replaceStrings ["/"] ["_"] "back-${gitPath}-${config.domain}";
      value = mkUnit gitPath config.port;
    })
    cfg.repositories;

  virtualHosts =
    lib.mapAttrs' (gitPath: config: {
      name = config.domain;
      value = mkVirtalHost config.port;
    })
    cfg.repositories;
in {
  options.vhack.back = {
    enable = lib.mkEnableOption "Back issue tracker (inspired by tvix's panettone)";

    repositories = lib.mkOption {
      description = "An attibute set of repos to launch `back` services for.";
      type = lib.types.attrsOf (lib.types.submodule {
        options = {
          enable = (lib.mkEnableOption "`back` for this repository.") // {default = true;};
          domain = lib.mkOption {
            type = lib.types.str;
            description = "The domain to host this `back` instance on.";
          };
          port = lib.mkOption {
            type = lib.types.port;

            # TODO: This _should_ be an implementation detail, but I've no real approach to
            # automatically generate them without encountering weird bugs. <2024-12-23>
            description = "The port to use for this back instance. This must be unique.";
          };
        };
      });
      default = {};
    };
  };

  config = lib.mkIf cfg.enable {
    systemd = {inherit services;};
    services.nginx = {inherit virtualHosts;};
  };
}