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

with lib;

let

  cfg = config.services.slurm;
  # configuration file can be generated by http://slurm.schedmd.com/configurator.html

  defaultUser = "slurm";

  configFile = pkgs.writeTextDir "slurm.conf"
    ''
      ClusterName=${cfg.clusterName}
      StateSaveLocation=${cfg.stateSaveLocation}
      SlurmUser=${cfg.user}
      ${optionalString (cfg.controlMachine != null) ''controlMachine=${cfg.controlMachine}''}
      ${optionalString (cfg.controlAddr != null) ''controlAddr=${cfg.controlAddr}''}
      ${optionalString (cfg.nodeName != null) ''nodeName=${cfg.nodeName}''}
      ${optionalString (cfg.partitionName != null) ''partitionName=${cfg.partitionName}''}
      PlugStackConfig=${plugStackConfig}
      ProctrackType=${cfg.procTrackType}
      ${cfg.extraConfig}
    '';

  plugStackConfig = pkgs.writeTextDir "plugstack.conf"
    ''
      ${optionalString cfg.enableSrunX11 ''optional ${pkgs.slurm-spank-x11}/lib/x11.so''}
      ${cfg.extraPlugstackConfig}
    '';

  cgroupConfig = pkgs.writeTextDir "cgroup.conf"
   ''
     ${cfg.extraCgroupConfig}
   '';

  slurmdbdConf = pkgs.writeTextDir "slurmdbd.conf"
   ''
     DbdHost=${cfg.dbdserver.dbdHost}
     SlurmUser=${cfg.user}
     StorageType=accounting_storage/mysql
     ${cfg.dbdserver.extraConfig}
   '';

  # slurm expects some additional config files to be
  # in the same directory as slurm.conf
  etcSlurm = pkgs.symlinkJoin {
    name = "etc-slurm";
    paths = [ configFile cgroupConfig plugStackConfig ];
  };

in

{

  ###### interface

  options = {

    services.slurm = {

      server = {
        enable = mkOption {
          type = types.bool;
          default = false;
          description = ''
            Wether to enable the slurm control daemon.
            Note that the standard authentication method is "munge".
            The "munge" service needs to be provided with a password file in order for
            slurm to work properly (see <literal>services.munge.password</literal>).
          '';
        };
      };

      dbdserver = {
        enable = mkEnableOption "SlurmDBD service";

        dbdHost = mkOption {
          type = types.str;
          default = config.networking.hostName;
          description = ''
            Hostname of the machine where <literal>slurmdbd</literal>
            is running (i.e. name returned by <literal>hostname -s</literal>).
          '';
        };

        extraConfig = mkOption {
          type = types.lines;
          default = "";
          description = ''
            Extra configuration for <literal>slurmdbd.conf</literal>
          '';
        };
      };

      client = {
        enable = mkEnableOption "slurm client daemon";
      };

      enableStools = mkOption {
        type = types.bool;
        default = false;
        description = ''
          Wether to provide a slurm.conf file.
          Enable this option if you do not run a slurm daemon on this host
          (i.e. <literal>server.enable</literal> and <literal>client.enable</literal> are <literal>false</literal>)
          but you still want to run slurm commands from this host.
        '';
      };

      package = mkOption {
        type = types.package;
        default = pkgs.slurm;
        defaultText = "pkgs.slurm";
        example = literalExample "pkgs.slurm-full";
        description = ''
          The package to use for slurm binaries.
        '';
      };

      controlMachine = mkOption {
        type = types.nullOr types.str;
        default = null;
        example = null;
        description = ''
          The short hostname of the machine where SLURM control functions are
          executed (i.e. the name returned by the command "hostname -s", use "tux001"
          rather than "tux001.my.com").
        '';
      };

      controlAddr = mkOption {
        type = types.nullOr types.str;
        default = cfg.controlMachine;
        example = null;
        description = ''
          Name that ControlMachine should be referred to in establishing a
          communications path.
        '';
      };

      clusterName = mkOption {
        type = types.str;
        default = "default";
        example = "myCluster";
        description = ''
          Necessary to distinguish accounting records in a multi-cluster environment.
        '';
      };

      nodeName = mkOption {
        type = types.nullOr types.str;
        default = null;
        example = "linux[1-32] CPUs=1 State=UNKNOWN";
        description = ''
          Name that SLURM uses to refer to a node (or base partition for BlueGene
          systems). Typically this would be the string that "/bin/hostname -s"
          returns. Note that now you have to write node's parameters after the name.
        '';
      };

      partitionName = mkOption {
        type = types.nullOr types.str;
        default = null;
        example = "debug Nodes=linux[1-32] Default=YES MaxTime=INFINITE State=UP";
        description = ''
          Name by which the partition may be referenced. Note that now you have
          to write the partition's parameters after the name.
        '';
      };

      enableSrunX11 = mkOption {
        default = false;
        type = types.bool;
        description = ''
          If enabled srun will accept the option "--x11" to allow for X11 forwarding
          from within an interactive session or a batch job. This activates the
          slurm-spank-x11 module. Note that this option also enables
          'services.openssh.forwardX11' on the client.

          This option requires slurm to be compiled without native X11 support.
        '';
      };

      procTrackType = mkOption {
        type = types.string;
        default = "proctrack/linuxproc";
        description = ''
          Plugin to be used for process tracking on a job step basis.
          The slurmd daemon uses this mechanism to identify all processes
          which are children of processes it spawns for a user job step.
        '';
      };

      stateSaveLocation = mkOption {
        type = types.str;
        default = "/var/spool/slurmctld";
        description = ''
          Directory into which the Slurm controller, slurmctld, saves its state.
        '';
      };

      user = mkOption {
        type = types.str;
        default = defaultUser;
        description = ''
          Set this option when you want to run the slurmctld daemon
          as something else than the default slurm user "slurm".
          Note that the UID of this user needs to be the same
          on all nodes.
        '';
      };

      extraConfig = mkOption {
        default = "";
        type = types.lines;
        description = ''
          Extra configuration options that will be added verbatim at
          the end of the slurm configuration file.
        '';
      };

      extraPlugstackConfig = mkOption {
        default = "";
        type = types.lines;
        description = ''
          Extra configuration that will be added to the end of <literal>plugstack.conf</literal>.
        '';
      };

      extraCgroupConfig = mkOption {
        default = "";
        type = types.lines;
        description = ''
          Extra configuration for <literal>cgroup.conf</literal>. This file is
          used when <literal>procTrackType=proctrack/cgroup</literal>.
        '';
      };


    };

  };


  ###### implementation

  config =
    let
      wrappedSlurm = pkgs.stdenv.mkDerivation {
        name = "wrappedSlurm";

        builder = pkgs.writeText "builder.sh" ''
          source $stdenv/setup
          mkdir -p $out/bin
          find  ${getBin cfg.package}/bin -type f -executable | while read EXE
          do
            exename="$(basename $EXE)"
            wrappername="$out/bin/$exename"
            cat > "$wrappername" <<EOT
          #!/bin/sh
          if [ -z "$SLURM_CONF" ]
          then
            SLURM_CONF="${etcSlurm}/slurm.conf" "$EXE" "\$@"
          else
            "$EXE" "\$0"
          fi
          EOT
            chmod +x "$wrappername"
          done

          mkdir -p $out/share
          ln -s ${getBin cfg.package}/share/man $out/share/man
        '';
      };

  in mkIf ( cfg.enableStools ||
            cfg.client.enable ||
            cfg.server.enable ||
            cfg.dbdserver.enable ) {

    environment.systemPackages = [ wrappedSlurm ];

    services.munge.enable = mkDefault true;

    # use a static uid as default to ensure it is the same on all nodes
    users.users.slurm = mkIf (cfg.user == defaultUser) {
      name = defaultUser;
      group = "slurm";
      uid = config.ids.uids.slurm;
    };

    users.groups.slurm.gid = config.ids.uids.slurm;

    systemd.services.slurmd = mkIf (cfg.client.enable) {
      path = with pkgs; [ wrappedSlurm coreutils ]
        ++ lib.optional cfg.enableSrunX11 slurm-spank-x11;

      wantedBy = [ "multi-user.target" ];
      after = [ "systemd-tmpfiles-clean.service" ];

      serviceConfig = {
        Type = "forking";
        ExecStart = "${wrappedSlurm}/bin/slurmd";
        PIDFile = "/run/slurmd.pid";
        ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
      };

      preStart = ''
        mkdir -p /var/spool
      '';
    };

    services.openssh.forwardX11 = mkIf cfg.client.enable (mkDefault true);

    systemd.services.slurmctld = mkIf (cfg.server.enable) {
      path = with pkgs; [ wrappedSlurm munge coreutils ]
        ++ lib.optional cfg.enableSrunX11 slurm-spank-x11;

      wantedBy = [ "multi-user.target" ];
      after = [ "network.target" "munged.service" ];
      requires = [ "munged.service" ];

      serviceConfig = {
        Type = "forking";
        ExecStart = "${wrappedSlurm}/bin/slurmctld";
        PIDFile = "/run/slurmctld.pid";
        ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
      };

      preStart = ''
        mkdir -p ${cfg.stateSaveLocation}
        chown -R ${cfg.user}:slurm ${cfg.stateSaveLocation}
      '';
    };

    systemd.services.slurmdbd = mkIf (cfg.dbdserver.enable) {
      path = with pkgs; [ wrappedSlurm munge coreutils ];

      wantedBy = [ "multi-user.target" ];
      after = [ "network.target" "munged.service" "mysql.service" ];
      requires = [ "munged.service" "mysql.service" ];

      # slurm strips the last component off the path
      environment.SLURM_CONF = "${slurmdbdConf}/slurm.conf";

      serviceConfig = {
        Type = "forking";
        ExecStart = "${cfg.package}/bin/slurmdbd";
        PIDFile = "/run/slurmdbd.pid";
        ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
      };
    };

  };

}