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

with lib;

let

  smbToString = x: if builtins.typeOf x == "bool"
                   then boolToString x
                   else toString x;

  cfg = config.services.samba;

  samba = cfg.package;

  shareConfig = name:
    let share = getAttr name cfg.shares; in
    "[${name}]\n " + (smbToString (
       map
         (key: "${key} = ${smbToString (getAttr key share)}\n")
         (attrNames share)
    ));

  configFile = pkgs.writeText "smb.conf"
    (if cfg.configText != null then cfg.configText else
    ''
      [global]
      security = ${cfg.securityType}
      passwd program = /run/wrappers/bin/passwd %u
      invalid users = ${smbToString cfg.invalidUsers}

      ${cfg.extraConfig}

      ${smbToString (map shareConfig (attrNames cfg.shares))}
    '');

  # This may include nss_ldap, needed for samba if it has to use ldap.
  nssModulesPath = config.system.nssModules.path;

  daemonService = appName: args:
    { description = "Samba Service Daemon ${appName}";

      after = [ (mkIf (cfg.enableNmbd && "${appName}" == "smbd") "samba-nmbd.service") ];
      requiredBy = [ "samba.target" ];
      partOf = [ "samba.target" ];

      environment = {
        LD_LIBRARY_PATH = nssModulesPath;
        LOCALE_ARCHIVE = "/run/current-system/sw/lib/locale/locale-archive";
      };

      serviceConfig = {
        ExecStart = "${samba}/sbin/${appName} --foreground --no-process-group ${args}";
        ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
        LimitNOFILE = 16384;
        PIDFile = "/run/${appName}.pid";
        Type = "notify";
        NotifyAccess = "all"; #may not do anything...
      };
      unitConfig.RequiresMountsFor = "/var/lib/samba";

      restartTriggers = [ configFile ];
    };

in

{
  imports = [
    (mkRemovedOptionModule [ "services" "samba" "defaultShare" ] "")
    (mkRemovedOptionModule [ "services" "samba" "syncPasswordsByPam" ] "This option has been removed by upstream, see https://bugzilla.samba.org/show_bug.cgi?id=10669#c10")
  ];

  ###### interface

  options = {

    # !!! clean up the descriptions.

    services.samba = {

      enable = mkOption {
        type = types.bool;
        default = false;
        description = lib.mdDoc ''
          Whether to enable Samba, which provides file and print
          services to Windows clients through the SMB/CIFS protocol.

          ::: {.note}
          If you use the firewall consider adding the following:

              services.samba.openFirewall = true;
          :::
        '';
      };

      openFirewall = mkOption {
        type = types.bool;
        default = false;
        description = lib.mdDoc ''
          Whether to automatically open the necessary ports in the firewall.
        '';
      };

      enableNmbd = mkOption {
        type = types.bool;
        default = true;
        description = lib.mdDoc ''
          Whether to enable Samba's nmbd, which replies to NetBIOS over IP name
          service requests. It also participates in the browsing protocols
          which make up the Windows "Network Neighborhood" view.
        '';
      };

      enableWinbindd = mkOption {
        type = types.bool;
        default = true;
        description = lib.mdDoc ''
          Whether to enable Samba's winbindd, which provides a number of services
          to the Name Service Switch capability found in most modern C libraries,
          to arbitrary applications via PAM and ntlm_auth and to Samba itself.
        '';
      };

      package = mkOption {
        type = types.package;
        default = pkgs.samba;
        defaultText = literalExpression "pkgs.samba";
        example = literalExpression "pkgs.samba4Full";
        description = lib.mdDoc ''
          Defines which package should be used for the samba server.
        '';
      };

      invalidUsers = mkOption {
        type = types.listOf types.str;
        default = [ "root" ];
        description = lib.mdDoc ''
          List of users who are denied to login via Samba.
        '';
      };

      extraConfig = mkOption {
        type = types.lines;
        default = "";
        description = lib.mdDoc ''
          Additional global section and extra section lines go in here.
        '';
        example = ''
          guest account = nobody
          map to guest = bad user
        '';
      };

      configText = mkOption {
        type = types.nullOr types.lines;
        default = null;
        description = lib.mdDoc ''
          Verbatim contents of smb.conf. If null (default), use the
          autogenerated file from NixOS instead.
        '';
      };

      securityType = mkOption {
        type = types.str;
        default = "user";
        description = lib.mdDoc "Samba security type";
      };

      nsswins = mkOption {
        default = false;
        type = types.bool;
        description = lib.mdDoc ''
          Whether to enable the WINS NSS (Name Service Switch) plug-in.
          Enabling it allows applications to resolve WINS/NetBIOS names (a.k.a.
          Windows machine names) by transparently querying the winbindd daemon.
        '';
      };

      shares = mkOption {
        default = {};
        description = lib.mdDoc ''
          A set describing shared resources.
          See {command}`man smb.conf` for options.
        '';
        type = types.attrsOf (types.attrsOf types.unspecified);
        example = literalExpression ''
          { public =
            { path = "/srv/public";
              "read only" = true;
              browseable = "yes";
              "guest ok" = "yes";
              comment = "Public samba share.";
            };
          }
        '';
      };

    };

  };


  ###### implementation

  config = mkMerge
    [ { assertions =
          [ { assertion = cfg.nsswins -> cfg.enableWinbindd;
              message   = "If samba.nsswins is enabled, then samba.enableWinbindd must also be enabled";
            }
          ];
        # Always provide a smb.conf to shut up programs like smbclient and smbspool.
        environment.etc."samba/smb.conf".source = mkOptionDefault (
          if cfg.enable then configFile
          else pkgs.writeText "smb-dummy.conf" "# Samba is disabled."
        );
      }

      (mkIf cfg.enable {

        system.nssModules = optional cfg.nsswins samba;
        system.nssDatabases.hosts = optional cfg.nsswins "wins";

        systemd = {
          targets.samba = {
            description = "Samba Server";
            after = [ "network.target" ];
            wants = [ "network-online.target" ];
            wantedBy = [ "multi-user.target" ];
          };
          # Refer to https://github.com/samba-team/samba/tree/master/packaging/systemd
          # for correct use with systemd
          services = {
            samba-smbd = daemonService "smbd" "";
            samba-nmbd = mkIf cfg.enableNmbd (daemonService "nmbd" "");
            samba-winbindd = mkIf cfg.enableWinbindd (daemonService "winbindd" "");
          };
          tmpfiles.rules = [
            "d /var/lock/samba - - - - -"
            "d /var/log/samba - - - - -"
            "d /var/cache/samba - - - - -"
            "d /var/lib/samba/private - - - - -"
          ];
        };

        security.pam.services.samba = {};
        environment.systemPackages = [ cfg.package ];

        networking.firewall.allowedTCPPorts = mkIf cfg.openFirewall [ 139 445 ];
        networking.firewall.allowedUDPPorts = mkIf cfg.openFirewall [ 137 138 ];
      })
    ];

}