let
  snakeoil_key = {
    id = "GK3515373e4c851ebaad366558";
    secret = "7d37d093435a41f2aab8f13c19ba067d9776c90215f56614adad6ece597dbb34";
  };
in
{ config, lib, pkgs, ... }: lib.mkMerge [
  { # garage setup
    services.garage = {
      ensureBuckets = {
        mastodon = {
          website = true;
          corsRules = {
            enable = true;
            allowedHeaders = [ "*" ];
            allowedMethods = [ "GET" ];
            allowedOrigins = [ "*" ];
          };
        };
      };
      ensureKeys = {
        mastodon = {
          inherit (snakeoil_key) id secret;
          ensureAccess = {
            mastodon = {
              read = true;
              write = true;
              owner = true;
            };
          };
        };
      };
    };
    services.mastodon = {
      extraConfig = rec {
        S3_ENABLED = "true";
        S3_ENDPOINT = "http://s3.garage.localhost:3900";
        S3_REGION = "garage";
        S3_BUCKET = "mastodon";
        # use <S3_BUCKET>.<S3_ENDPOINT>
        S3_OVERRIDE_PATH_STLE = "true";
        AWS_ACCESS_KEY_ID = snakeoil_key.id;
        AWS_SECRET_ACCESS_KEY = snakeoil_key.secret;
        S3_PROTOCOL = "http";
        S3_HOSTNAME = "web.garage.localhost:3902";
        # by default it tries to use "<S3_HOSTNAME>/<S3_BUCKET>"
        S3_ALIAS_HOST = "${S3_BUCKET}.${S3_HOSTNAME}";
        # SEE: the last section in https://docs.joinmastodon.org/admin/optional/object-storage/
        # TODO: can we set up ACLs with garage?
        S3_PERMISSION = "";
      };
    };
  }
  # 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
  {
    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 = lib.max 1 (config.virtualisation.cores - 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;
      }
    ];
  }

  # run mastodon as development environment
  {
    networking.firewall.allowedTCPPorts = [ 55001 ];
    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";
        # to be accessible from outside the VM
        BIND = "0.0.0.0";
        # for letter_opener (still doesn't work though)
        REMOTE_DEV = "true";
        LOCAL_DOMAIN = "mastodon.localhost:8443";
      };
    };

    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" ];
    };

    # Currently, nixos seems to be able to create a single database per
    # postgres user. This works for the production version of mastodon, which
    # is what's packaged in nixpkgs. For development, we need two databases,
    # mastodon_development and mastodon_test. This used to be possible with
    # ensurePermissions, but that's broken and has been removed. Here I copy
    # the mastodon-init-db script from upstream nixpkgs, but add the single
    # line `rails db:setup`, which asks mastodon to create the postgres
    # databases for us.
    # FIXME: the commented out lines were breaking things, but presumably they're necessary for something.
    # TODO: see if we can fix the upstream ensurePermissions stuff. See above for what that config would look like.
    systemd.services.mastodon-init-db.script = lib.mkForce ''
      result="$(psql -t --csv -c \
          "select count(*) from pg_class c \
          join pg_namespace s on s.oid = c.relnamespace \
          where s.nspname not in ('pg_catalog', 'pg_toast', 'information_schema') \
          and s.nspname not like 'pg_temp%';")" || error_code=$?
      if [ "''${error_code:-0}" -ne 0 ]; then
        echo "Failure checking if database is seeded. psql gave exit code $error_code"
        exit "$error_code"
      fi
      if [ "$result" -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)"
        # rails db:migrate
      fi
    '';
    virtualisation.forwardPorts = [
      {
        from = "host";
        host.port = 55001;
        guest.port = 55001;
      }
    ];
  }
]