nixpkgs/nixos/modules/services/networking/prayer.nix

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

with lib;

let

  inherit (pkgs) prayer;

  cfg = config.services.prayer;

  stateDir = "/var/lib/prayer";

  prayerUser = "prayer";
  prayerGroup = "prayer";

  prayerExtraCfg = pkgs.writeText "extraprayer.cf" ''
    prefix = "${prayer}"
    var_prefix = "${stateDir}"
    prayer_user = "${prayerUser}"
    prayer_group = "${prayerGroup}"
    sendmail_path = "/run/wrappers/bin/sendmail"

    use_http_port ${cfg.port}

    ${cfg.extraConfig}
  '';

  prayerCfg = pkgs.runCommand "prayer.cf" { preferLocalBuild = true; } ''
    # We have to remove the http_port 80, or it will start a server there
    cat ${prayer}/etc/prayer.cf | grep -v http_port > $out
    cat ${prayerExtraCfg} >> $out
  '';

in

{

  ###### interface

  options = {

    services.prayer = {

      enable = mkOption {
        default = false;
        description = ''
          Whether to run the prayer webmail http server.
        '';
      };

      port = mkOption {
        default = "2080";
        description = ''
          Port the prayer http server is listening to.
        '';
      };

      extraConfig = mkOption {
        type = types.lines;
        default = "" ;
        description = ''
          Extra configuration. Contents will be added verbatim to the configuration file.
        '';
      };
    };

  };


  ###### implementation

  config = mkIf config.services.prayer.enable {
    environment.systemPackages = [ prayer ];

    users.users.${prayerUser} =
      { uid = config.ids.uids.prayer;
        description = "Prayer daemon user";
        home = stateDir;
      };

    users.groups.${prayerGroup} =
      { gid = config.ids.gids.prayer; };

    systemd.services.prayer = {
      wantedBy = [ "multi-user.target" ];
      serviceConfig.Type = "forking";
      preStart = ''
        mkdir -m 0755 -p ${stateDir}
        chown ${prayerUser}.${prayerGroup} ${stateDir}
      '';
      script = "${prayer}/sbin/prayer --config-file=${prayerCfg}";
    };
  };
}