nix-darwin/modules/services/hercules-ci-agent/default.nix

{ config, lib, pkgs, ... }:

with lib;

let
  cfg = config.services.hercules-ci-agent;
  user = config.users.users.hercules-ci-agent;
in {
  options.services.hercules-ci-agent = {
    enable = mkOption {
      type = types.bool;
      default = false;
      description = "Run Hercules CI Agent as a system service";
    };

    apiBaseUrl = mkOption {
      description = "Alternative base URL for the Hercules API";
      example = "https://hercules-ci.com";
      default = null;
      type = types.nullOr types.string;
    };

    clusterJoinTokenPath = mkOption {
      description = ''
        Location of a the cluster join token. It authorizes the agent to add
        itself to the cluster that the token represents.

        This file is only required to be present for the agent's first run. It
        will be ignored after the agent has used the token successfully.
      '';
      type = types.path;
    };

    logFile = mkOption {
      type = types.path;
      default = "/var/log/hercules-ci-agent.log";
      description = "Stdout and sterr of hercules-ci-agent process.";
    };

    concurrentTasks = mkOption {
      description = "Number of tasks to perform simultaneously, such as evaluations, derivations";
      type = types.int;
      default = 4;
    };

    package = mkOption {
      type = types.package;
      default = (import (builtins.fetchTarball "https://github.com/hercules-ci/hercules-ci-agent/archive/stable.tar.gz")).nixos-19_03.hercules-ci-agent;
      description = ''
        Package containing the bin/hercules-ci-agent program.
      '';
    };
  };

  config = mkIf cfg.enable {
    launchd.daemons.hercules-ci-agent = {
      script = ''
        exec ${cfg.package}/bin/hercules-ci-agent \
          ${if (cfg.apiBaseUrl == null) then "" else "--api-base-url ${escapeShellArg cfg.apiBaseUrl}"} \
          --cluster-join-token-path ${escapeShellArg cfg.clusterJoinTokenPath} \
          --concurrent-tasks ${toString cfg.concurrentTasks}
      '';

      path = [ config.nix.package ];
      environment = {
        NIX_SSL_CERT_FILE = "${pkgs.cacert}/etc/ssl/certs/ca-bundle.crt";
      };

      serviceConfig.KeepAlive = true;
      serviceConfig.RunAtLoad = true;
      serviceConfig.StandardErrorPath = cfg.logFile;
      serviceConfig.StandardOutPath = cfg.logFile;
      serviceConfig.GroupName = "hercules-ci-agent";
      serviceConfig.UserName = "hercules-ci-agent";
      serviceConfig.WorkingDirectory = user.home;
      serviceConfig.WatchPaths = [
        cfg.clusterJoinTokenPath
      ];
    };

    system.activationScripts.preActivation.text = ''
      touch '${cfg.logFile}'
      chown ${toString user.uid}:${toString user.gid} '${cfg.logFile}'
    '';

    users.knownGroups = [ "hercules-ci-agent" ];
    users.knownUsers = [ "hercules-ci-agent" ];

    services.hercules-ci-agent.clusterJoinTokenPath = lib.mkDefault (user.home + "/agent-join-token.key");

    users.users.hercules-ci-agent = {
      uid = mkDefault 532;
      gid = mkDefault config.users.groups.hercules-ci-agent.gid;
      home = mkDefault "/var/lib/hercules-ci-agent";
      createHome = true;
      shell = "/bin/bash";
      description = "System user for the Hercules CI Agent";
    };
    users.groups.hercules-ci-agent = {
      gid = mkDefault 532;
      description = "System group for the Hercules CI Agent";
    };
  };
}