{ config, lib, pkgs, ...}:
with lib;
let
  cfg = config.services.hadoop;
  hadoopConf = "${import ./conf.nix { inherit cfg pkgs lib; }}/";
  restartIfChanged  = mkOption {
    type = types.bool;
    description = ''
      Automatically restart the service on config change.
      This can be set to false to defer restarts on clusters running critical applications.
      Please consider the security implications of inadvertently running an older version,
      and the possibility of unexpected behavior caused by inconsistent versions across a cluster when disabling this option.
    '';
    default = false;
  };
in
{
  options.services.hadoop.hdfs = {
    namenode = {
      enabled = mkOption {
        type = types.bool;
        default = false;
        description = ''
          Whether to run the HDFS NameNode
        '';
      };
      inherit restartIfChanged;
      openFirewall = mkOption {
        type = types.bool;
        default = true;
        description = ''
          Open firewall ports for namenode
        '';
      };
    };
    datanode = {
      enabled = mkOption {
        type = types.bool;
        default = false;
        description = ''
          Whether to run the HDFS DataNode
        '';
      };
      inherit restartIfChanged;
      openFirewall = mkOption {
        type = types.bool;
        default = true;
        description = ''
          Open firewall ports for datanode
        '';
      };
    };
  };

  config = mkMerge [
    (mkIf cfg.hdfs.namenode.enabled {
      systemd.services.hdfs-namenode = {
        description = "Hadoop HDFS NameNode";
        wantedBy = [ "multi-user.target" ];
        inherit (cfg.hdfs.namenode) restartIfChanged;

        preStart = ''
          ${cfg.package}/bin/hdfs --config ${hadoopConf} namenode -format -nonInteractive || true
        '';

        serviceConfig = {
          User = "hdfs";
          SyslogIdentifier = "hdfs-namenode";
          ExecStart = "${cfg.package}/bin/hdfs --config ${hadoopConf} namenode";
          Restart = "always";
        };
      };

      networking.firewall.allowedTCPPorts = (mkIf cfg.hdfs.namenode.openFirewall [
        9870 # namenode.http-address
        8020 # namenode.rpc-address
      ]);
    })
    (mkIf cfg.hdfs.datanode.enabled {
      systemd.services.hdfs-datanode = {
        description = "Hadoop HDFS DataNode";
        wantedBy = [ "multi-user.target" ];
        inherit (cfg.hdfs.datanode) restartIfChanged;

        serviceConfig = {
          User = "hdfs";
          SyslogIdentifier = "hdfs-datanode";
          ExecStart = "${cfg.package}/bin/hdfs --config ${hadoopConf} datanode";
          Restart = "always";
        };
      };

      networking.firewall.allowedTCPPorts = (mkIf cfg.hdfs.datanode.openFirewall [
        9864 # datanode.http.address
        9866 # datanode.address
        9867 # datanode.ipc.address
      ]);
    })
    (mkIf (
        cfg.hdfs.namenode.enabled || cfg.hdfs.datanode.enabled
    ) {
      users.users.hdfs = {
        description = "Hadoop HDFS user";
        group = "hadoop";
        uid = config.ids.uids.hdfs;
      };
    })

  ];
}