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

with lib;

let
  cfg = config.services.cassandra;
  defaultUser = "cassandra";
  cassandraConfig = flip recursiveUpdate cfg.extraConfig
    ({ commitlog_sync = "batch";
       commitlog_sync_batch_window_in_ms = 2;
       start_native_transport = cfg.allowClients;
       cluster_name = cfg.clusterName;
       partitioner = "org.apache.cassandra.dht.Murmur3Partitioner";
       endpoint_snitch = "SimpleSnitch";
       seed_provider =
         [{ class_name = "org.apache.cassandra.locator.SimpleSeedProvider";
            parameters = [ { seeds = concatStringsSep "," cfg.seedAddresses; } ];
         }];
       data_file_directories = [ "${cfg.homeDir}/data" ];
       commitlog_directory = "${cfg.homeDir}/commitlog";
       saved_caches_directory = "${cfg.homeDir}/saved_caches";
     } // (if lib.versionAtLeast cfg.package.version "3"
             then { hints_directory = "${cfg.homeDir}/hints"; }
             else {})
    );
  cassandraConfigWithAddresses = cassandraConfig //
    ( if cfg.listenAddress == null
        then { listen_interface = cfg.listenInterface; }
        else { listen_address = cfg.listenAddress; }
    ) // (
      if cfg.rpcAddress == null
        then { rpc_interface = cfg.rpcInterface; }
        else { rpc_address = cfg.rpcAddress; }
    );
  cassandraEtc = pkgs.stdenv.mkDerivation
    { name = "cassandra-etc";
      cassandraYaml = builtins.toJSON cassandraConfigWithAddresses;
      cassandraEnvPkg = "${cfg.package}/conf/cassandra-env.sh";
      cassandraLogbackConfig = pkgs.writeText "logback.xml" cfg.logbackConfig;
      buildCommand = ''
        mkdir -p "$out"

        echo "$cassandraYaml" > "$out/cassandra.yaml"
        ln -s "$cassandraLogbackConfig" "$out/logback.xml"

        cp "$cassandraEnvPkg" "$out/cassandra-env.sh"

        # Delete default JMX Port, otherwise we can't set it using env variable
        sed -i '/JMX_PORT="7199"/d' "$out/cassandra-env.sh"

        # Delete default password file
        sed -i '/-Dcom.sun.management.jmxremote.password.file=\/etc\/cassandra\/jmxremote.password/d' "$out/cassandra-env.sh"
      '';
    };
  defaultJmxRolesFile = builtins.foldl'
     (left: right: left + right) ""
     (map (role: "${role.username} ${role.password}") cfg.jmxRoles);
  fullJvmOptions = cfg.jvmOpts
    ++ lib.optionals (cfg.jmxRoles != []) [
      "-Dcom.sun.management.jmxremote.authenticate=true"
      "-Dcom.sun.management.jmxremote.password.file=${cfg.jmxRolesFile}"
    ]
    ++ lib.optionals cfg.remoteJmx [
      "-Djava.rmi.server.hostname=${cfg.rpcAddress}"
    ];
in {
  options.services.cassandra = {
    enable = mkEnableOption ''
      Apache Cassandra – Scalable and highly available database.
    '';
    clusterName = mkOption {
      type = types.str;
      default = "NixOS Test Cluster";
      description = ''
        The name of the cluster.
        This setting prevents nodes in one logical cluster from joining
        another. All nodes in a cluster must have the same value.
      '';
    };
    user = mkOption {
      type = types.str;
      default = defaultUser;
      description = "Run Apache Cassandra under this user.";
    };
    group = mkOption {
      type = types.str;
      default = defaultUser;
      description = "Run Apache Cassandra under this group.";
    };
    homeDir = mkOption {
      type = types.path;
      default = "/var/lib/cassandra";
      description = ''
        Home directory for Apache Cassandra.
      '';
    };
    package = mkOption {
      type = types.package;
      default = pkgs.cassandra;
      defaultText = "pkgs.cassandra";
      example = literalExample "pkgs.cassandra_3_11";
      description = ''
        The Apache Cassandra package to use.
      '';
    };
    jvmOpts = mkOption {
      type = types.listOf types.str;
      default = [];
      description = ''
        Populate the JVM_OPT environment variable.
      '';
    };
    listenAddress = mkOption {
      type = types.nullOr types.str;
      default = "127.0.0.1";
      example = literalExample "null";
      description = ''
        Address or interface to bind to and tell other Cassandra nodes
        to connect to. You _must_ change this if you want multiple
        nodes to be able to communicate!

        Set listenAddress OR listenInterface, not both.

        Leaving it blank leaves it up to
        InetAddress.getLocalHost(). This will always do the Right
        Thing _if_ the node is properly configured (hostname, name
        resolution, etc), and the Right Thing is to use the address
        associated with the hostname (it might not be).

        Setting listen_address to 0.0.0.0 is always wrong.
      '';
    };
    listenInterface = mkOption {
      type = types.nullOr types.str;
      default = null;
      example = "eth1";
      description = ''
        Set listenAddress OR listenInterface, not both. Interfaces
        must correspond to a single address, IP aliasing is not
        supported.
      '';
    };
    rpcAddress = mkOption {
      type = types.nullOr types.str;
      default = "127.0.0.1";
      example = literalExample "null";
      description = ''
        The address or interface to bind the native transport server to.

        Set rpcAddress OR rpcInterface, not both.

        Leaving rpcAddress blank has the same effect as on
        listenAddress (i.e. it will be based on the configured hostname
        of the node).

        Note that unlike listenAddress, you can specify 0.0.0.0, but you
        must also set extraConfig.broadcast_rpc_address to a value other
        than 0.0.0.0.

        For security reasons, you should not expose this port to the
        internet. Firewall it if needed.
      '';
    };
    rpcInterface = mkOption {
      type = types.nullOr types.str;
      default = null;
      example = "eth1";
      description = ''
        Set rpcAddress OR rpcInterface, not both. Interfaces must
        correspond to a single address, IP aliasing is not supported.
      '';
    };
    logbackConfig = mkOption {
      type = types.lines;
      default = ''
        <configuration scan="false">
          <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
            <encoder>
              <pattern>%-5level %date{HH:mm:ss,SSS} %msg%n</pattern>
            </encoder>
          </appender>

          <root level="INFO">
            <appender-ref ref="STDOUT" />
          </root>

          <logger name="com.thinkaurelius.thrift" level="ERROR"/>
        </configuration>
      '';
      description = ''
        XML logback configuration for cassandra
      '';
    };
    seedAddresses = mkOption {
      type = types.listOf types.str;
      default = [ "127.0.0.1" ];
      description = ''
        The addresses of hosts designated as contact points in the cluster. A
        joining node contacts one of the nodes in the seeds list to learn the
        topology of the ring.
        Set to 127.0.0.1 for a single node cluster.
      '';
    };
    allowClients = mkOption {
      type = types.bool;
      default = true;
      description = ''
        Enables or disables the native transport server (CQL binary protocol).
        This server uses the same address as the <literal>rpcAddress</literal>,
        but the port it uses is not <literal>rpc_port</literal> but
        <literal>native_transport_port</literal>. See the official Cassandra
        docs for more information on these variables and set them using
        <literal>extraConfig</literal>.
      '';
    };
    extraConfig = mkOption {
      type = types.attrs;
      default = {};
      example =
        { commitlog_sync_batch_window_in_ms = 3;
        };
      description = ''
        Extra options to be merged into cassandra.yaml as nix attribute set.
      '';
    };
    fullRepairInterval = mkOption {
      type = types.nullOr types.str;
      default = "3w";
      example = literalExample "null";
      description = ''
          Set the interval how often full repairs are run, i.e.
          `nodetool repair --full` is executed. See
          https://cassandra.apache.org/doc/latest/operating/repair.html
          for more information.

          Set to `null` to disable full repairs.
        '';
    };
    fullRepairOptions = mkOption {
      type = types.listOf types.str;
      default = [];
      example = [ "--partitioner-range" ];
      description = ''
          Options passed through to the full repair command.
        '';
    };
    incrementalRepairInterval = mkOption {
      type = types.nullOr types.str;
      default = "3d";
      example = literalExample "null";
      description = ''
          Set the interval how often incremental repairs are run, i.e.
          `nodetool repair` is executed. See
          https://cassandra.apache.org/doc/latest/operating/repair.html
          for more information.

          Set to `null` to disable incremental repairs.
        '';
    };
    incrementalRepairOptions = mkOption {
      type = types.listOf types.string;
      default = [];
      example = [ "--partitioner-range" ];
      description = ''
          Options passed through to the incremental repair command.
        '';
    };
    maxHeapSize = mkOption {
      type = types.nullOr types.string;
      default = null;
      example = "4G";
      description = ''
        Must be left blank or set together with heapNewSize.
        If left blank a sensible value for the available amount of RAM and CPU
        cores is calculated.

        Override to set the amount of memory to allocate to the JVM at
        start-up. For production use you may wish to adjust this for your
        environment. MAX_HEAP_SIZE is the total amount of memory dedicated
        to the Java heap. HEAP_NEWSIZE refers to the size of the young
        generation.

        The main trade-off for the young generation is that the larger it
        is, the longer GC pause times will be. The shorter it is, the more
        expensive GC will be (usually).
      '';
    };
    heapNewSize = mkOption {
      type = types.nullOr types.string;
      default = null;
      example = "800M";
      description = ''
        Must be left blank or set together with heapNewSize.
        If left blank a sensible value for the available amount of RAM and CPU
        cores is calculated.

        Override to set the amount of memory to allocate to the JVM at
        start-up. For production use you may wish to adjust this for your
        environment. HEAP_NEWSIZE refers to the size of the young
        generation.

        The main trade-off for the young generation is that the larger it
        is, the longer GC pause times will be. The shorter it is, the more
        expensive GC will be (usually).

        The example HEAP_NEWSIZE assumes a modern 8-core+ machine for decent pause
        times. If in doubt, and if you do not particularly want to tweak, go with
        100 MB per physical CPU core.
      '';
    };
    mallocArenaMax = mkOption {
      type = types.nullOr types.int;
      default = null;
      example = 4;
      description = ''
        Set this to control the amount of arenas per-thread in glibc.
      '';
    };
    remoteJmx = mkOption {
      type = types.bool;
      default = false;
      description = ''
        Cassandra ships with JMX accessible *only* from localhost.
        To enable remote JMX connections set to true.

        Be sure to also enable authentication and/or TLS.
        See: https://wiki.apache.org/cassandra/JmxSecurity
      '';
    };
    jmxPort = mkOption {
      type = types.int;
      default = 7199;
      description = ''
        Specifies the default port over which Cassandra will be available for
        JMX connections.
        For security reasons, you should not expose this port to the internet.
        Firewall it if needed.
      '';
    };
    jmxRoles = mkOption {
      default = [];
      description = ''
        Roles that are allowed to access the JMX (e.g. nodetool)
        BEWARE: The passwords will be stored world readable in the nix-store.

        Doesn't work in versions older than 3.11 because they don't like that
        it's world readable.
      '';
      type = types.listOf (types.submodule {
        options = {
          username = mkOption {
            type = types.string;
            description = "Username for JMX";
          };
          password = mkOption {
            type = types.string;
            description = "Password for JMX";
          };
        };
      });
    };
    jmxRolesFile = mkOption {
      type = types.nullOr types.path;
      default = if (lib.versionAtLeast cfg.package.version "3.11")
                then pkgs.writeText "jmx-roles-file" defaultJmxRolesFile
                else null;
      example = "/var/lib/cassandra/jmx.password";
      description = ''
        Specify your own jmx roles file.

        Make sure the permissions forbid "others" from reading the file if
        you're using Cassandra below version 3.11.
      '';
    };
  };

  config = mkIf cfg.enable {
    assertions =
      [ { assertion = (cfg.listenAddress == null) != (cfg.listenInterface == null);
          message = "You have to set either listenAddress or listenInterface";
        }
        { assertion = (cfg.rpcAddress == null) != (cfg.rpcInterface == null);
          message = "You have to set either rpcAddress or rpcInterface";
        }
        { assertion = (cfg.maxHeapSize == null) == (cfg.heapNewSize == null);
          message = "If you set either of maxHeapSize or heapNewSize you have to set both";
        }
        { assertion = cfg.remoteJmx -> cfg.jmxRolesFile != null;
          message = ''
            If you want JMX available remotely you need to set a password using
            `jmxRoles` or `jmxRolesFile` if using Cassandra older than v3.11.
          '';
        }
      ];
    users = mkIf (cfg.user == defaultUser) {
      extraUsers."${defaultUser}" =
        {  group = cfg.group;
           home = cfg.homeDir;
           createHome = true;
           uid = config.ids.uids.cassandra;
           description = "Cassandra service user";
        };
      extraGroups."${defaultUser}".gid = config.ids.gids.cassandra;
    };

    systemd.services.cassandra =
      { description = "Apache Cassandra service";
        after = [ "network.target" ];
        environment =
          { CASSANDRA_CONF = "${cassandraEtc}";
            JVM_OPTS = builtins.concatStringsSep " " fullJvmOptions;
            MAX_HEAP_SIZE = toString cfg.maxHeapSize;
            HEAP_NEWSIZE = toString cfg.heapNewSize;
            MALLOC_ARENA_MAX = toString cfg.mallocArenaMax;
            LOCAL_JMX = if cfg.remoteJmx then "no" else "yes";
            JMX_PORT = toString cfg.jmxPort;
          };
        wantedBy = [ "multi-user.target" ];
        serviceConfig =
          { User = cfg.user;
            Group = cfg.group;
            ExecStart = "${cfg.package}/bin/cassandra -f";
            SuccessExitStatus = 143;
          };
      };

    systemd.services.cassandra-full-repair =
      { description = "Perform a full repair on this Cassandra node";
        after = [ "cassandra.service" ];
        requires = [ "cassandra.service" ];
        serviceConfig =
          { User = cfg.user;
            Group = cfg.group;
            ExecStart =
              lib.concatStringsSep " "
                ([ "${cfg.package}/bin/nodetool" "repair" "--full"
                 ] ++ cfg.fullRepairOptions);
          };
      };
    systemd.timers.cassandra-full-repair =
      mkIf (cfg.fullRepairInterval != null) {
        description = "Schedule full repairs on Cassandra";
        wantedBy = [ "timers.target" ];
        timerConfig =
          { OnBootSec = cfg.fullRepairInterval;
            OnUnitActiveSec = cfg.fullRepairInterval;
            Persistent = true;
          };
      };

    systemd.services.cassandra-incremental-repair =
      { description = "Perform an incremental repair on this cassandra node.";
        after = [ "cassandra.service" ];
        requires = [ "cassandra.service" ];
        serviceConfig =
          { User = cfg.user;
            Group = cfg.group;
            ExecStart =
              lib.concatStringsSep " "
                ([ "${cfg.package}/bin/nodetool" "repair"
                 ] ++ cfg.incrementalRepairOptions);
          };
      };
    systemd.timers.cassandra-incremental-repair =
      mkIf (cfg.incrementalRepairInterval != null) {
        description = "Schedule incremental repairs on Cassandra";
        wantedBy = [ "timers.target" ];
        timerConfig =
          { OnBootSec = cfg.incrementalRepairInterval;
            OnUnitActiveSec = cfg.incrementalRepairInterval;
            Persistent = true;
          };
      };
  };
}