{
  config,
  lib,
  pkgs,
}: let
  cfg = config.services.versia-server;
  configFormat = pkgs.formats.toml {};
  name = "versia-server";

  inherit (lib.options) mkOption;
  inherit (lib.modules) mkIf;
in {
  options = {
    services.versia-server = {
      enable = mkOption {
        type = lib.types.bool;
        default = false;
        description = ''
          Enable the Versia Server services.
        '';
      };

      dataDir = mkOption {
        type = lib.types.path;
        default = "/var/lib/${name}";
        description = ''
          Directory where the server will store its data.
        '';
      };

      user = mkOption {
        type = lib.types.str;
        default = name;
        description = ''
          User under which the server will run.
        '';
      };

      group = mkOption {
        type = lib.types.str;
        default = name;
        description = ''
          Group under which the server will run.
        '';
      };

      nodes = {
        api = mkOption {
          type = lib.types.attrsOf lib.types.submodule {
            options = {
              configOverrides = mkOption {
                type = lib.types.submodule {
                  freeformType = configFormat.type;
                  options = {};
                };
                description = "Overrides for the node's configuration file.";
              };
            };
          };
        };
        worker = mkOption {
          type = lib.types.attrsOf lib.types.submodule {
            options = {
              configOverrides = mkOption {
                type = lib.types.submodule {
                  freeformType = configFormat.type;
                  options = {};
                };
                description = "Overrides for the node's configuration file.";
              };
            };
          };
        };
      };

      config = mkOption {
        type = lib.types.submodule {
          freeformType = configFormat.type;
          options = {};
        };
        description = "Contents of the config file. Check the Versia Server documentation for information on its contents.";
      };
    };
  };

  config = mkIf cfg.enable {
    assertions = [
      {
        assertion = cfg.nodes.api != [];
        message = "At least one API node must be defined.";
      }
      {
        assertion = cfg.nodes.worker != [];
        message = "At least one worker node must be defined.";
      }
    ];
  };

  systemd.services =
    builtins.mapAttrs (nodeName: node: let
      config = cfg.config // node.configOverrides;
      configFile = builtins.toFile (configFormat.generate "config-${nodeName}" config);
    in {
      after = ["network-online.target"];
      wantedBy = ["multi-user.target"];
      requires = ["network-online.target"];

      serviceConfig = {
        Type = "simple";
        Restart = "always";

        User = cfg.user;
        Group = cfg.group;

        StateDirectory = "${name}";
        StateDirectoryMode = "0700";
        RuntimeDirectory = "${name}";
        RuntimeDirectoryMode = "0700";

        # Set the working directory to the data directory
        WorkingDirectory = cfg.dataDir;

        StandardOutput = "journal";
        StandardError = "journal";
        SyslogIdentifier = "${name}";

        Environment = [
          "CONFIG_FILE=${configFile}"
        ];
      };
      path = [pkgs.versia-server];
    }) (cfg.nodes.api ++ cfg.nodes.worker)
    // builtins.mapAttrs (nodeName: node: let
      type = "api";
      exe = lib.getExe pkgs.versia-server;
    in {
      name = "${name}-${type}-${nodeName}";
      description = "Versia Server ${node.name} (${type})";

      serviceConfig.ExecStart = "${exe}";
    }) (cfg.nodes.api)
    // builtins.mapAttrs (nodeName: node: let
      type = "worker";
      exe = lib.getExe pkgs.versia-server-worker;
    in {
      name = "${name}-${type}-${nodeName}";
      description = "Versia Server ${node.name} (${type})";

      serviceConfig.ExecStart = "${exe}";
    }) (cfg.nodes.worker);

  systemd.tmpfiles.rules = [
    {
      # Create the data directory with the correct permissions
      line = "d ${cfg.dataDir} - - - - ${cfg.user} ${cfg.group}";
    }
  ];

  users = {
    groups = {
      "${cfg.group}" = {
        description = "Group for the Versia Server";
      };
    };

    users = {
      "${cfg.user}" = {
        isSystemUser = true;
        group = cfg.group;
        home = cfg.dataDir;
        packages = [pkgs.versia-server pkgs.versia-server-worker];
      };
    };
  };
}