{ config, lib, pkgs, ... }: lib.mkMerge [
  # not mastodon related
  {
    # let us log in
    users.mutableUsers = false;
    users.users.root.hashedPassword = "";
    services.openssh = {
      enable = true;
      settings = {
        PermitRootLogin = "yes";
        PermitEmptyPasswords = "yes";
        UsePAM = "no";
      };
    };

    # access to convenient things
    environment.systemPackages = with pkgs; [ w3m python3 ];
    nix.extraOptions = ''
      extra-experimental-features = nix-command flakes
    '';
  }

  # mastodon setup
  {
    # open up access to the mastodon web interface
    networking.firewall.allowedTCPPorts = [ 443 ];

    services.mastodon = {
      enable = true;

      # TODO: set up a domain name, and a DNS service so that this can run not in a vm
      # localDomain = "domain.social";
      configureNginx = true;

      # TODO: configure a mailserver so this works
      # smtp.fromAddress = "mastodon@mastodon.localhost";

      # TODO: this is hardware-dependent. let's figure it out when we have hardware
      # streamingProcesses = 1;
    };

    security.acme = {
      acceptTerms = true;
      preliminarySelfsigned = true;
      # TODO: configure a mailserver so we can set up acme
      # defaults.email = "test@example.com";
    };
  }

  # VM setup
  {
    # these configurations only apply when producing a VM (e.g. nixos-rebuild build-vm)
    virtualisation.vmVariant = { config, ... }: {
      services.mastodon = {
        # redirects to localhost, but allows it to have a proper domain name
        localDomain = "mastodon.localhost";

        smtp = {
          fromAddress = "mastodon@mastodon.localhost";
          createLocally = false;
        };

        extraConfig = {
          EMAIL_DOMAIN_ALLOWLIST = "example.com";
        };

        # from the documentation: recommended is the amount of your CPU cores minus one.
        # but it also must be a positive integer
        streamingProcesses = let
          ncores = config.virtualisation.cores;
          max = x: y: if x > y then x else y;
        in
          max 1 (ncores - 1);
      };

      security.acme = {
        defaults = {
          # invalid server; the systemd service will fail, and we won't get properly signed certificates
          # but let's not spam the letsencrypt servers (and we don't own this domain anyways)
          server = "https://127.0.0.1";
          email = "none";
        };
      };

      virtualisation.memorySize = 2048;
      virtualisation.forwardPorts = [
        {
          from = "host";
          host.port = 44443;
          guest.port = 443;
        }
        {
          from = "host";
          host.port = 2222;
          guest.port = 22;
        }
      ];
    };
  }

  # mastodon development environment
  {
    virtualisation.vmVariant = { config, ... }: {
      services.mastodon = {
        # needed so we can directly access mastodon at port 55001
        # otherwise, mastodon has to be accessed *from* port 443, which we can't do via port forwarding
        enableUnixSocket = false;
        extraConfig = {
          RAILS_ENV = "development";
          # for letter_opener
          REMOTE_DEV = "true";
        };
      };

      services.postgresql = {
        enable = true;
        ensureUsers = [
          {
            name = config.services.mastodon.database.user;
            ensureClauses.createdb = true;
            # ensurePermissions doesn't work anymore
            # ensurePermissions = {
            #   "mastodon_development.*" = "ALL PRIVILEGES";
            #   "mastodon_test.*" = "ALL PRIVILEGES";
            # }
          }
        ];
        # ensureDatabases = [ "mastodon_development_test" "mastodon_test" ];
      };

      # run rails db:seed so that mastodon sets up the databases for us
      systemd.services.mastodon-init-db.script = lib.mkForce ''
          if [ `psql -c \
                  "select count(*) from pg_class c \
                  join pg_namespace s on s.oid = c.relnamespace \
                  where s.nspname not in ('pg_catalog', 'pg_toast', 'information_schema') \
                  and s.nspname not like 'pg_temp%';" | sed -n 3p` -eq 0 ]; then
            echo "Seeding database"
            rails db:setup
            # SAFETY_ASSURED=1 rails db:schema:load
            rails db:seed
          else
            echo "Migrating database (this might be a noop)"
            # TODO: this breaks for some reason
            # rails db:migrate
          fi
      '';
      virtualisation.forwardPorts = lib.mkForce [
        {
          from = "host";
          host.port = 55001;
          guest.port = 55001;
        }
      ];
    };
  }
]