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

with lib;

let
  cfg = config.services.thanos;

  nullOpt = type: description: mkOption {
    type = types.nullOr type;
    default = null;
    inherit description;
  };

  optionToArgs = opt: v  : optional (v != null)  ''--${opt}="${toString v}"'';
  flagToArgs   = opt: v  : optional v            ''--${opt}'';
  listToArgs   = opt: vs : map               (v: ''--${opt}="${v}"'') vs;
  attrsToArgs  = opt: kvs: mapAttrsToList (k: v: ''--${opt}=${k}=\"${v}\"'') kvs;

  mkParamDef = type: default: description: mkParam type (description + ''

    Defaults to <literal>${toString default}</literal> in Thanos
    when set to <literal>null</literal>.
  '');

  mkParam = type: description: {
    toArgs = optionToArgs;
    option = nullOpt type description;
  };

  mkFlagParam = description: {
    toArgs = flagToArgs;
    option = mkOption {
      type = types.bool;
      default = false;
      inherit description;
    };
  };

  mkListParam = opt: description: {
    toArgs = _opt: listToArgs opt;
    option = mkOption {
      type = types.listOf types.str;
      default = [];
      inherit description;
    };
  };

  mkAttrsParam = opt: description: {
    toArgs = _opt: attrsToArgs opt;
    option = mkOption {
      type = types.attrsOf types.str;
      default = {};
      inherit description;
    };
  };

  mkStateDirParam = opt: default: description: {
    toArgs = _opt: stateDir: optionToArgs opt "/var/lib/${stateDir}";
    option = mkOption {
      type = types.str;
      inherit default;
      inherit description;
    };
  };

  toYAML = name: attrs: pkgs.runCommandNoCC name {
    preferLocalBuild = true;
    json = builtins.toFile "${name}.json" (builtins.toJSON attrs);
    nativeBuildInputs = [ pkgs.remarshal ];
  } ''json2yaml -i $json -o $out'';

  thanos = cmd: "${cfg.package}/bin/thanos ${cmd}" +
    (let args = cfg.${cmd}.arguments;
     in optionalString (length args != 0) (" \\\n  " +
         concatStringsSep " \\\n  " args));

  argumentsOf = cmd: concatLists (collect isList
    (flip mapParamsRecursive params.${cmd} (path: param:
      let opt = concatStringsSep "." path;
          v = getAttrFromPath path cfg.${cmd};
      in param.toArgs opt v)));

  mkArgumentsOption = cmd: mkOption {
    type = types.listOf types.str;
    default = argumentsOf cmd;
    description = ''
      Arguments to the <literal>thanos ${cmd}</literal> command.

      Defaults to a list of arguments formed by converting the structured
      options of <option>services.thanos.${cmd}</option> to a list of arguments.

      Overriding this option will cause none of the structured options to have
      any effect. So only set this if you know what you're doing!
    '';
  };

  mapParamsRecursive =
    let noParam = attr: !(attr ? toArgs && attr ? option);
    in mapAttrsRecursiveCond noParam;

  paramsToOptions = mapParamsRecursive (_path: param: param.option);

  params = {

    log = {

      log.level = mkParamDef (types.enum ["debug" "info" "warn" "error" "fatal"]) "info" ''
        Log filtering level.
      '';

      log.format = mkParam types.str ''
        Log format to use.
      '';
    };

    tracing = cfg: {
      tracing.config-file = {
        toArgs = _opt: path: optionToArgs "tracing.config-file" path;
        option = mkOption {
          type = with types; nullOr str;
          default = if cfg.tracing.config == null then null
                    else toString (toYAML "tracing.yaml" cfg.tracing.config);
          defaultText = ''
            if config.services.thanos.<cmd>.tracing.config == null then null
            else toString (toYAML "tracing.yaml" config.services.thanos.<cmd>.tracing.config);
          '';
          description = ''
            Path to YAML file that contains tracing configuration.
          '';
        };
      };

      tracing.config =
        {
          toArgs = _opt: _attrs: [];
          option = nullOpt types.attrs ''
            Tracing configuration.

            When not <literal>null</literal> the attribute set gets converted to
            a YAML file and stored in the Nix store. The option
            <option>tracing.config-file</option> will default to its path.

            If <option>tracing.config-file</option> is set this option has no effect.
          '';
        };
    };

    common = cfg: params.log // params.tracing cfg // {

      http-address = mkParamDef types.str "0.0.0.0:10902" ''
        Listen <literal>host:port</literal> for HTTP endpoints.
      '';

      grpc-address = mkParamDef types.str "0.0.0.0:10901" ''
        Listen <literal>ip:port</literal> address for gRPC endpoints (StoreAPI).

        Make sure this address is routable from other components.
      '';

      grpc-server-tls-cert = mkParam types.str ''
        TLS Certificate for gRPC server, leave blank to disable TLS
      '';

      grpc-server-tls-key = mkParam types.str ''
        TLS Key for the gRPC server, leave blank to disable TLS
      '';

      grpc-server-tls-client-ca = mkParam types.str ''
        TLS CA to verify clients against.

        If no client CA is specified, there is no client verification on server side.
        (tls.NoClientCert)
      '';
    };

    objstore = cfg: {

      objstore.config-file = {
        toArgs = _opt: path: optionToArgs "objstore.config-file" path;
        option = mkOption {
          type = with types; nullOr str;
          default = if cfg.objstore.config == null then null
                    else toString (toYAML "objstore.yaml" cfg.objstore.config);
          defaultText = ''
            if config.services.thanos.<cmd>.objstore.config == null then null
            else toString (toYAML "objstore.yaml" config.services.thanos.<cmd>.objstore.config);
          '';
          description = ''
            Path to YAML file that contains object store configuration.
          '';
        };
      };

      objstore.config =
        {
          toArgs = _opt: _attrs: [];
          option = nullOpt types.attrs ''
            Object store configuration.

            When not <literal>null</literal> the attribute set gets converted to
            a YAML file and stored in the Nix store. The option
            <option>objstore.config-file</option> will default to its path.

            If <option>objstore.config-file</option> is set this option has no effect.
          '';
        };
    };

    sidecar = params.common cfg.sidecar // params.objstore cfg.sidecar // {

      prometheus.url = mkParamDef types.str "http://localhost:9090" ''
        URL at which to reach Prometheus's API.

        For better performance use local network.
      '';

      tsdb.path = {
        toArgs = optionToArgs;
        option = mkOption {
          type = types.str;
          default = "/var/lib/${config.services.prometheus.stateDir}/data";
          defaultText = "/var/lib/\${config.services.prometheus.stateDir}/data";
          description = ''
            Data directory of TSDB.
          '';
        };
      };

      reloader.config-file = mkParam types.str ''
        Config file watched by the reloader.
      '';

      reloader.config-envsubst-file = mkParam types.str ''
        Output file for environment variable substituted config file.
      '';

      reloader.rule-dirs = mkListParam "reloader.rule-dir" ''
        Rule directories for the reloader to refresh.
      '';

    };

    store = params.common cfg.store // params.objstore cfg.store // {

      stateDir = mkStateDirParam "data-dir" "thanos-store" ''
        Data directory relative to <literal>/var/lib</literal>
        in which to cache remote blocks.
      '';

      index-cache-size = mkParamDef types.str "250MB" ''
        Maximum size of items held in the index cache.
      '';

      chunk-pool-size = mkParamDef types.str "2GB" ''
        Maximum size of concurrently allocatable bytes for chunks.
      '';

      store.grpc.series-sample-limit = mkParamDef types.int 0 ''
        Maximum amount of samples returned via a single Series call.

        <literal>0</literal> means no limit.

        NOTE: for efficiency we take 120 as the number of samples in chunk (it
        cannot be bigger than that), so the actual number of samples might be
        lower, even though the maximum could be hit.
      '';

      store.grpc.series-max-concurrency = mkParamDef types.int 20 ''
        Maximum number of concurrent Series calls.
      '';

      sync-block-duration = mkParamDef types.str "3m" ''
        Repeat interval for syncing the blocks between local and remote view.
      '';

      block-sync-concurrency = mkParamDef types.int 20 ''
        Number of goroutines to use when syncing blocks from object storage.
      '';
    };

    query = params.common cfg.query // {

      grpc-client-tls-secure = mkFlagParam ''
        Use TLS when talking to the gRPC server
      '';

      grpc-client-tls-cert = mkParam types.str ''
        TLS Certificates to use to identify this client to the server
      '';

      grpc-client-tls-key = mkParam types.str ''
        TLS Key for the client's certificate
      '';

      grpc-client-tls-ca = mkParam types.str ''
        TLS CA Certificates to use to verify gRPC servers
      '';

      grpc-client-server-name = mkParam types.str ''
        Server name to verify the hostname on the returned gRPC certificates.
        See <link xlink:href="https://tools.ietf.org/html/rfc4366#section-3.1"/>
      '';

      web.route-prefix = mkParam types.str ''
        Prefix for API and UI endpoints.

        This allows thanos UI to be served on a sub-path. This option is
        analogous to <option>web.route-prefix</option> of Promethus.
      '';

      web.external-prefix = mkParam types.str ''
        Static prefix for all HTML links and redirect URLs in the UI query web
        interface.

        Actual endpoints are still served on / or the
        <option>web.route-prefix</option>. This allows thanos UI to be served
        behind a reverse proxy that strips a URL sub-path.
      '';

      web.prefix-header = mkParam types.str ''
        Name of HTTP request header used for dynamic prefixing of UI links and
        redirects.

        This option is ignored if the option
        <literal>web.external-prefix</literal> is set.

        Security risk: enable this option only if a reverse proxy in front of
        thanos is resetting the header.

        The setting <literal>web.prefix-header="X-Forwarded-Prefix"</literal>
        can be useful, for example, if Thanos UI is served via Traefik reverse
        proxy with <literal>PathPrefixStrip</literal> option enabled, which
        sends the stripped prefix value in <literal>X-Forwarded-Prefix</literal>
        header. This allows thanos UI to be served on a sub-path.
      '';

      query.timeout = mkParamDef types.str "2m" ''
        Maximum time to process query by query node.
      '';

      query.max-concurrent = mkParamDef types.int 20 ''
        Maximum number of queries processed concurrently by query node.
      '';

      query.replica-label = mkParam types.str ''
        Label to treat as a replica indicator along which data is
        deduplicated.

        Still you will be able to query without deduplication using
        <literal>dedup=false</literal> parameter.
      '';

      selector-labels = mkAttrsParam "selector-label" ''
        Query selector labels that will be exposed in info endpoint.
      '';

      store.addresses = mkListParam "store" ''
        Addresses of statically configured store API servers.

        The scheme may be prefixed with <literal>dns+</literal> or
        <literal>dnssrv+</literal> to detect store API servers through
        respective DNS lookups.
      '';

      store.sd-files = mkListParam "store.sd-files" ''
        Path to files that contain addresses of store API servers. The path
        can be a glob pattern.
      '';

      store.sd-interval = mkParamDef types.str "5m" ''
        Refresh interval to re-read file SD files. It is used as a resync fallback.
      '';

      store.sd-dns-interval = mkParamDef types.str "30s" ''
        Interval between DNS resolutions.
      '';

      store.unhealthy-timeout = mkParamDef types.str "5m" ''
        Timeout before an unhealthy store is cleaned from the store UI page.
      '';

      query.auto-downsampling = mkFlagParam ''
        Enable automatic adjustment (step / 5) to what source of data should
        be used in store gateways if no
        <literal>max_source_resolution</literal> param is specified.
      '';

      query.partial-response = mkFlagParam ''
        Enable partial response for queries if no
        <literal>partial_response</literal> param is specified.
      '';

      query.default-evaluation-interval = mkParamDef types.str "1m" ''
        Set default evaluation interval for sub queries.
      '';

      store.response-timeout = mkParamDef types.str "0ms" ''
        If a Store doesn't send any data in this specified duration then a
        Store will be ignored and partial data will be returned if it's
        enabled. <literal>0</literal> disables timeout.
      '';
    };

    rule = params.common cfg.rule // params.objstore cfg.rule // {

      labels = mkAttrsParam "label" ''
        Labels to be applied to all generated metrics.

        Similar to external labels for Prometheus,
        used to identify ruler and its blocks as unique source.
      '';

      stateDir = mkStateDirParam "data-dir" "thanos-rule" ''
        Data directory relative to <literal>/var/lib</literal>.
      '';

      rule-files = mkListParam "rule-file" ''
        Rule files that should be used by rule manager. Can be in glob format.
      '';

      eval-interval = mkParamDef types.str "30s" ''
        The default evaluation interval to use.
      '';

      tsdb.block-duration = mkParamDef types.str "2h" ''
        Block duration for TSDB block.
      '';

      tsdb.retention = mkParamDef types.str "48h" ''
        Block retention time on local disk.
      '';

      alertmanagers.urls = mkListParam "alertmanagers.url" ''
        Alertmanager replica URLs to push firing alerts.

        Ruler claims success if push to at least one alertmanager from
        discovered succeeds. The scheme may be prefixed with
        <literal>dns+</literal> or <literal>dnssrv+</literal> to detect
        Alertmanager IPs through respective DNS lookups. The port defaults to
        <literal>9093</literal> or the SRV record's value. The URL path is
        used as a prefix for the regular Alertmanager API path.
      '';

      alertmanagers.send-timeout = mkParamDef types.str "10s" ''
        Timeout for sending alerts to alertmanager.
      '';

      alert.query-url = mkParam types.str ''
        The external Thanos Query URL that would be set in all alerts 'Source' field.
      '';

      alert.label-drop = mkListParam "alert.label-drop" ''
        Labels by name to drop before sending to alertmanager.

        This allows alert to be deduplicated on replica label.

        Similar Prometheus alert relabelling
      '';

      web.route-prefix = mkParam types.str ''
        Prefix for API and UI endpoints.

        This allows thanos UI to be served on a sub-path.

        This option is analogous to <literal>--web.route-prefix</literal> of Promethus.
      '';

      web.external-prefix = mkParam types.str ''
        Static prefix for all HTML links and redirect URLs in the UI query web
        interface.

        Actual endpoints are still served on / or the
        <option>web.route-prefix</option>. This allows thanos UI to be served
        behind a reverse proxy that strips a URL sub-path.
      '';

      web.prefix-header = mkParam types.str ''
        Name of HTTP request header used for dynamic prefixing of UI links and
        redirects.

        This option is ignored if the option
        <option>web.external-prefix</option> is set.

        Security risk: enable this option only if a reverse proxy in front of
        thanos is resetting the header.

        The header <literal>X-Forwarded-Prefix</literal> can be useful, for
        example, if Thanos UI is served via Traefik reverse proxy with
        <literal>PathPrefixStrip</literal> option enabled, which sends the
        stripped prefix value in <literal>X-Forwarded-Prefix</literal>
        header. This allows thanos UI to be served on a sub-path.
      '';

      query.addresses = mkListParam "query" ''
        Addresses of statically configured query API servers.

        The scheme may be prefixed with <literal>dns+</literal> or
        <literal>dnssrv+</literal> to detect query API servers through
        respective DNS lookups.
      '';

      query.sd-files = mkListParam "query.sd-files" ''
        Path to file that contain addresses of query peers.
        The path can be a glob pattern.
      '';

      query.sd-interval = mkParamDef types.str "5m" ''
        Refresh interval to re-read file SD files. (used as a fallback)
      '';

      query.sd-dns-interval = mkParamDef types.str "30s" ''
        Interval between DNS resolutions.
      '';
    };

    compact = params.log // params.tracing cfg.compact // params.objstore cfg.compact // {

      http-address = mkParamDef types.str "0.0.0.0:10902" ''
        Listen <literal>host:port</literal> for HTTP endpoints.
      '';

      stateDir = mkStateDirParam "data-dir" "thanos-compact" ''
        Data directory relative to <literal>/var/lib</literal>
        in which to cache blocks and process compactions.
      '';

      consistency-delay = mkParamDef types.str "30m" ''
        Minimum age of fresh (non-compacted) blocks before they are being
        processed. Malformed blocks older than the maximum of consistency-delay
        and 30m0s will be removed.
      '';

      retention.resolution-raw = mkParamDef types.str "0d" ''
        How long to retain raw samples in bucket.

        <literal>0d</literal> - disables this retention
      '';

      retention.resolution-5m = mkParamDef types.str "0d" ''
        How long to retain samples of resolution 1 (5 minutes) in bucket.

        <literal>0d</literal> - disables this retention
      '';

      retention.resolution-1h = mkParamDef types.str "0d" ''
        How long to retain samples of resolution 2 (1 hour) in bucket.

        <literal>0d</literal> - disables this retention
      '';

      startAt = {
        toArgs = _opt: startAt: flagToArgs "wait" (startAt == null);
        option = nullOpt types.str ''
          When this option is set to a <literal>systemd.time</literal>
          specification the Thanos compactor will run at the specified period.

          When this option is <literal>null</literal> the Thanos compactor service
          will run continuously. So it will not exit after all compactions have
          been processed but wait for new work.
        '';
      };

      block-sync-concurrency = mkParamDef types.int 20 ''
        Number of goroutines to use when syncing block metadata from object storage.
      '';

      compact.concurrency = mkParamDef types.int 1 ''
        Number of goroutines to use when compacting groups.
      '';
    };

    downsample = params.log // params.tracing cfg.downsample // params.objstore cfg.downsample // {

      stateDir = mkStateDirParam "data-dir" "thanos-downsample" ''
        Data directory relative to <literal>/var/lib</literal>
        in which to cache blocks and process downsamplings.
      '';

    };

    receive = params.common cfg.receive // params.objstore cfg.receive // {

      remote-write.address = mkParamDef types.str "0.0.0.0:19291" ''
        Address to listen on for remote write requests.
      '';

      stateDir = mkStateDirParam "tsdb.path" "thanos-receive" ''
        Data directory relative to <literal>/var/lib</literal> of TSDB.
      '';

      labels = mkAttrsParam "labels" ''
        External labels to announce.

        This flag will be removed in the future when handling multiple tsdb
        instances is added.
      '';

      tsdb.retention = mkParamDef types.str "15d" ''
        How long to retain raw samples on local storage.

        <literal>0d</literal> - disables this retention
      '';
    };

  };

  assertRelativeStateDir = cmd: {
    assertions = [
      {
        assertion = !hasPrefix "/" cfg.${cmd}.stateDir;
        message =
          "The option services.thanos.${cmd}.stateDir should not be an absolute directory." +
          " It should be a directory relative to /var/lib.";
      }
    ];
  };

in {

  options.services.thanos = {

    package = mkOption {
      type = types.package;
      default = pkgs.thanos;
      defaultText = "pkgs.thanos";
      description = ''
        The thanos package that should be used.
      '';
    };

    sidecar = paramsToOptions params.sidecar // {
      enable = mkEnableOption
        "the Thanos sidecar for Prometheus server";
      arguments = mkArgumentsOption "sidecar";
    };

    store = paramsToOptions params.store // {
      enable = mkEnableOption
        "the Thanos store node giving access to blocks in a bucket provider.";
      arguments = mkArgumentsOption "store";
    };

    query = paramsToOptions params.query // {
      enable = mkEnableOption
        ("the Thanos query node exposing PromQL enabled Query API " +
         "with data retrieved from multiple store nodes");
      arguments = mkArgumentsOption "query";
    };

    rule = paramsToOptions params.rule // {
      enable = mkEnableOption
        ("the Thanos ruler service which evaluates Prometheus rules against" +
        " given Query nodes, exposing Store API and storing old blocks in bucket");
      arguments = mkArgumentsOption "rule";
    };

    compact = paramsToOptions params.compact // {
      enable = mkEnableOption
        "the Thanos compactor which continuously compacts blocks in an object store bucket";
      arguments = mkArgumentsOption "compact";
    };

    downsample = paramsToOptions params.downsample // {
      enable = mkEnableOption
        "the Thanos downsampler which continuously downsamples blocks in an object store bucket";
      arguments = mkArgumentsOption "downsample";
    };

    receive = paramsToOptions params.receive // {
      enable = mkEnableOption
        ("the Thanos receiver which accept Prometheus remote write API requests " +
         "and write to local tsdb (EXPERIMENTAL, this may change drastically without notice)");
      arguments = mkArgumentsOption "receive";
    };
  };

  config = mkMerge [

    (mkIf cfg.sidecar.enable {
      assertions = [
        {
          assertion = config.services.prometheus.enable;
          message =
            "Please enable services.prometheus when enabling services.thanos.sidecar.";
        }
        {
          assertion = !(config.services.prometheus.globalConfig.external_labels == null ||
                        config.services.prometheus.globalConfig.external_labels == {});
          message =
            "services.thanos.sidecar requires uniquely identifying external labels " +
            "to be configured in the Prometheus server. " +
            "Please set services.prometheus.globalConfig.external_labels.";
        }
      ];
      systemd.services.thanos-sidecar = {
        wantedBy = [ "multi-user.target" ];
        after    = [ "network.target" "prometheus.service" ];
        serviceConfig = {
          User = "prometheus";
          Restart = "always";
          ExecStart = thanos "sidecar";
        };
      };
    })

    (mkIf cfg.store.enable (mkMerge [
      (assertRelativeStateDir "store")
      {
        systemd.services.thanos-store = {
          wantedBy = [ "multi-user.target" ];
          after    = [ "network.target" ];
          serviceConfig = {
            DynamicUser = true;
            StateDirectory = cfg.store.stateDir;
            Restart = "always";
            ExecStart = thanos "store";
          };
        };
      }
    ]))

    (mkIf cfg.query.enable {
      systemd.services.thanos-query = {
        wantedBy = [ "multi-user.target" ];
        after    = [ "network.target" ];
        serviceConfig = {
          DynamicUser = true;
          Restart = "always";
          ExecStart = thanos "query";
        };
      };
    })

    (mkIf cfg.rule.enable (mkMerge [
      (assertRelativeStateDir "rule")
      {
        systemd.services.thanos-rule = {
          wantedBy = [ "multi-user.target" ];
          after    = [ "network.target" ];
          serviceConfig = {
            DynamicUser = true;
            StateDirectory = cfg.rule.stateDir;
            Restart = "always";
            ExecStart = thanos "rule";
          };
        };
      }
    ]))

    (mkIf cfg.compact.enable (mkMerge [
      (assertRelativeStateDir "compact")
      {
        systemd.services.thanos-compact =
          let wait = cfg.compact.startAt == null; in {
            wantedBy = [ "multi-user.target" ];
            after    = [ "network.target" ];
            serviceConfig = {
              Type    = if wait then "simple" else "oneshot";
              Restart = if wait then "always" else "no";
              DynamicUser = true;
              StateDirectory = cfg.compact.stateDir;
              ExecStart = thanos "compact";
            };
          } // optionalAttrs (!wait) { inherit (cfg.compact) startAt; };
      }
    ]))

    (mkIf cfg.downsample.enable (mkMerge [
      (assertRelativeStateDir "downsample")
      {
        systemd.services.thanos-downsample = {
          wantedBy = [ "multi-user.target" ];
          after    = [ "network.target" ];
          serviceConfig = {
            DynamicUser = true;
            StateDirectory = cfg.downsample.stateDir;
            Restart = "always";
            ExecStart = thanos "downsample";
          };
        };
      }
    ]))

    (mkIf cfg.receive.enable (mkMerge [
      (assertRelativeStateDir "receive")
      {
        systemd.services.thanos-receive = {
          wantedBy = [ "multi-user.target" ];
          after    = [ "network.target" ];
          serviceConfig = {
            DynamicUser = true;
            StateDirectory = cfg.receive.stateDir;
            Restart = "always";
            ExecStart = thanos "receive";
          };
        };
      }
    ]))

  ];
}