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

with lib;

let
  cfg = config.services.graphite;
  writeTextOrNull = f: t: if t == null then null else pkgs.writeTextDir f t;

  dataDir = cfg.dataDir;

  graphiteApiConfig = pkgs.writeText "graphite-api.yaml" ''
    time_zone: ${config.time.timeZone}
    search_index: ${dataDir}/index
    ${optionalString (cfg.api.finders != []) ''finders:''}
    ${concatMapStringsSep "\n" (f: "  - " + f.moduleName) cfg.api.finders}
    ${optionalString (cfg.api.functions != []) ''functions:''}
    ${concatMapStringsSep "\n" (f: "  - " + f) cfg.api.functions}
    ${cfg.api.extraConfig}
  '';

  seyrenConfig = {
    SEYREN_URL = cfg.seyren.seyrenUrl;
    MONGO_URL = cfg.seyren.mongoUrl;
    GRAPHITE_URL = cfg.seyren.graphiteUrl;
  } // cfg.seyren.extraConfig;

  pagerConfig = pkgs.writeText "alarms.yaml" cfg.pager.alerts;

  configDir = pkgs.buildEnv {
    name = "graphite-config";
    paths = lists.filter (el: el != null) [
      (writeTextOrNull "carbon.conf" cfg.carbon.config)
      (writeTextOrNull "storage-aggregation.conf" cfg.carbon.storageAggregation)
      (writeTextOrNull "storage-schemas.conf" cfg.carbon.storageSchemas)
      (writeTextOrNull "blacklist.conf" cfg.carbon.blacklist)
      (writeTextOrNull "whitelist.conf" cfg.carbon.whitelist)
      (writeTextOrNull "rewrite-rules.conf" cfg.carbon.rewriteRules)
      (writeTextOrNull "relay-rules.conf" cfg.carbon.relayRules)
      (writeTextOrNull "aggregation-rules.conf" cfg.carbon.aggregationRules)
    ];
  };

  carbonOpts = name: with config.ids; ''
    --nodaemon --syslog --prefix=${name} --pidfile ${dataDir}/${name}.pid ${name}
  '';
  carbonEnv = {
    PYTHONPATH = "${pkgs.python27Packages.carbon}/lib/python2.7/site-packages";
    GRAPHITE_ROOT = dataDir;
    GRAPHITE_CONF_DIR = configDir;
    GRAPHITE_STORAGE_DIR = dataDir;
  };

in {

  ###### interface

  options.services.graphite = {
    dataDir = mkOption {
      type = types.path;
      default = "/var/db/graphite";
      description = ''
        Data directory for graphite.
      '';
    };

    web = {
      enable = mkOption {
        description = "Whether to enable graphite web frontend.";
        default = false;
        type = types.uniq types.bool;
      };

      host = mkOption {
        description = "Graphite web frontend listen address.";
        default = "127.0.0.1";
        type = types.str;
      };

      port = mkOption {
        description = "Graphite web frontend port.";
        default = 8080;
        type = types.int;
      };
    };

    api = {
      enable = mkOption {
        description = ''
          Whether to enable graphite api. Graphite api is lightweight alternative
          to graphite web, with api and without dashboard. It's advised to use
          grafana as alternative dashboard and influxdb as alternative to
          graphite carbon.

          For more information visit
          <link xlink:href="http://graphite-api.readthedocs.org/en/latest/"/>
        '';
        default = false;
        type = types.uniq types.bool;
      };

      finders = mkOption {
        description = "List of finder plugins to load.";
        default = [];
        example = [ pkgs.python27Packages.graphite_influxdb ];
        type = types.listOf types.package;
      };

      functions = mkOption {
        description = "List of functions to load.";
        default = [
          "graphite_api.functions.SeriesFunctions"
          "graphite_api.functions.PieFunctions"
        ];
        type = types.listOf types.str;
      };

      host = mkOption {
        description = "Graphite web service listen address.";
        default = "127.0.0.1";
        type = types.str;
      };

      port = mkOption {
        description = "Graphite api service port.";
        default = 8080;
        type = types.int;
      };

      package = mkOption {
        description = "Package to use for graphite api.";
        default = pkgs.python27Packages.graphite_api;
        type = types.package;
      };

      extraConfig = mkOption {
        description = "Extra configuration for graphite api.";
        default = ''
          whisper:
            directories:
                - ${dataDir}/whisper
        '';
        example = literalExample ''
          allowed_origins:
            - dashboard.example.com
          cheat_times: true
          influxdb:
            host: localhost
            port: 8086
            user: influxdb
            pass: influxdb
            db: metrics
          cache:
            CACHE_TYPE: 'filesystem'
            CACHE_DIR: '/tmp/graphite-api-cache'
        '';
        type = types.str;
      };
    };

    carbon = {
      config = mkOption {
        description = "Content of carbon configuration file.";
        default = ''
          [cache]
          # Listen on localhost by default for security reasons
          UDP_RECEIVER_INTERFACE = 127.0.0.1
          PICKLE_RECEIVER_INTERFACE = 127.0.0.1
          LINE_RECEIVER_INTERFACE = 127.0.0.1
          CACHE_QUERY_INTERFACE = 127.0.0.1
          # Do not log every update
          LOG_UPDATES = False
          LOG_CACHE_HITS = False
        '';
        type = types.str;
      };

      enableCache = mkOption {
        description = "Whether to enable carbon cache, the graphite storage daemon.";
        default = false;
        type = types.uniq types.bool;
      };

      storageAggregation = mkOption {
        description = "Defines how to aggregate data to lower-precision retentions.";
        default = null;
        type = types.uniq (types.nullOr types.string);
        example = ''
          [all_min]
          pattern = \.min$
          xFilesFactor = 0.1
          aggregationMethod = min
        '';
      };

      storageSchemas = mkOption {
        description = "Defines retention rates for storing metrics.";
        default = "";
        type = types.uniq (types.nullOr types.string);
        example = ''
          [apache_busyWorkers]
          pattern = ^servers\.www.*\.workers\.busyWorkers$
          retentions = 15s:7d,1m:21d,15m:5y
        '';
      };

      blacklist = mkOption {
        description = "Any metrics received which match one of the experssions will be dropped.";
        default = null;
        type = types.uniq (types.nullOr types.string);
        example = "^some\.noisy\.metric\.prefix\..*";
      };

      whitelist = mkOption {
        description = "Only metrics received which match one of the experssions will be persisted.";
        default = null;
        type = types.uniq (types.nullOr types.string);
        example = ".*";
      };

      rewriteRules = mkOption {
        description = ''
          Regular expression patterns that can be used to rewrite metric names
          in a search and replace fashion.
        '';
        default = null;
        type = types.uniq (types.nullOr types.string);
        example = ''
          [post]
          _sum$ =
          _avg$ =
        '';
      };

      enableRelay = mkOption {
        description = "Whether to enable carbon relay, the carbon replication and sharding service.";
        default = false;
        type = types.uniq types.bool;
      };

      relayRules = mkOption {
        description = "Relay rules are used to send certain metrics to a certain backend.";
        default = null;
        type = types.uniq (types.nullOr types.string);
        example = ''
          [example]
          pattern = ^mydata\.foo\..+
          servers = 10.1.2.3, 10.1.2.4:2004, myserver.mydomain.com
        '';
      };

      enableAggregator = mkOption {
        description = "Whether to enable carbon agregator, the carbon buffering service.";
        default = false;
        type = types.uniq types.bool;
      };

      aggregationRules = mkOption {
        description = "Defines if and how received metrics will be agregated.";
        default = null;
        type = types.uniq (types.nullOr types.string);
        example = ''
          <env>.applications.<app>.all.requests (60) = sum <env>.applications.<app>.*.requests
          <env>.applications.<app>.all.latency (60) = avg <env>.applications.<app>.*.latency
        '';
      };
    };

    seyren = {
      enable = mkOption {
        description = "Whether to enable seyren service.";
        default = false;
        type = types.uniq types.bool;
      };

      port = mkOption {
        description = "Seyren listening port.";
        default = 8081;
        type = types.int;
      };

      seyrenUrl = mkOption {
        default = "http://localhost:${toString cfg.seyren.port}/";
        description = "Host where seyren is accessible.";
        type = types.str;
      };

      graphiteUrl = mkOption {
        default = "http://${cfg.web.host}:${toString cfg.web.port}";
        description = "Host where graphite service runs.";
        type = types.str;
      };

      mongoUrl = mkOption {
        default = "mongodb://${config.services.mongodb.bind_ip}:27017/seyren";
        description = "Mongodb connection string.";
        type = types.str;
      };

      extraConfig = mkOption {
        default = {};
        description = ''
          Extra seyren configuration. See
          <link xlink:href='https://github.com/scobal/seyren#config' />
        '';
        type = types.attrsOf types.str;
        example = literalExample ''
          {
            GRAPHITE_USERNAME = "user";
            GRAPHITE_PASSWORD = "pass";
          }
        '';
      };
    };

    pager = {
      enable = mkOption {
        description = ''
          Whether to enable graphite-pager service. For more information visit
          <link xlink:href="https://github.com/seatgeek/graphite-pager"/>
        '';
        default = false;
        type = types.uniq types.bool;
      };

      redisUrl = mkOption {
        description = "Redis connection string.";
        default = "redis://localhost:${toString config.services.redis.port}/";
        type = types.str;
      };

      graphiteUrl = mkOption {
        description = "URL to your graphite service.";
        default = "http://${cfg.web.host}:${toString cfg.web.port}";
        type = types.str;
      };

      alerts = mkOption {
        description = "Alerts configuration for graphite-pager.";
        default = ''
          alerts:
            - target: constantLine(100)
              warning: 90
              critical: 200
              name: Test
        '';
        example = literalExample ''
          pushbullet_key: pushbullet_api_key
          alerts:
            - target: stats.seatgeek.app.deal_quality.venue_info_cache.hit
              warning: .5
              critical: 1
              name: Deal quality venue cache hits
        '';
        type = types.lines;
      };
    };
  };

  ###### implementation

  config = mkMerge [
    (mkIf cfg.carbon.enableCache {
      systemd.services.carbonCache = {
        description = "Graphite Data Storage Backend";
        wantedBy = [ "multi-user.target" ];
        after = [ "network-interfaces.target" ];
        environment = carbonEnv;
        serviceConfig = {
          ExecStart = "${pkgs.twisted}/bin/twistd ${carbonOpts "carbon-cache"}";
          User = "graphite";
          Group = "graphite";
          PermissionsStartOnly = true;
        };
        preStart = ''
          mkdir -p ${cfg.dataDir}/whisper
          chmod 0700 ${cfg.dataDir}/whisper
          chown -R graphite:graphite ${cfg.dataDir}
        '';
      };
    })

    (mkIf cfg.carbon.enableAggregator {
      systemd.services.carbonAggregator = {
        enable = cfg.carbon.enableAggregator;
        description = "Carbon Data Aggregator";
        wantedBy = [ "multi-user.target" ];
        after = [ "network-interfaces.target" ];
        environment = carbonEnv;
        serviceConfig = {
          ExecStart = "${pkgs.twisted}/bin/twistd ${carbonOpts "carbon-aggregator"}";
          User = "graphite";
          Group = "graphite";
        };
      };
    })

    (mkIf cfg.carbon.enableRelay {
      systemd.services.carbonRelay = {
        description = "Carbon Data Relay";
        wantedBy = [ "multi-user.target" ];
        after = [ "network-interfaces.target" ];
        environment = carbonEnv;
        serviceConfig = {
          ExecStart = "${pkgs.twisted}/bin/twistd ${carbonOpts "carbon-relay"}";
          User = "graphite";
          Group = "graphite";
        };
      };
    })

    (mkIf (cfg.carbon.enableCache || cfg.carbon.enableAggregator || cfg.carbon.enableRelay) {
      environment.systemPackages = [
        pkgs.pythonPackages.carbon
      ];
    })

    (mkIf cfg.web.enable {
      systemd.services.graphiteWeb = {
        description = "Graphite Web Interface";
        wantedBy = [ "multi-user.target" ];
        after = [ "network-interfaces.target" ];
        path = [ pkgs.perl ];
        environment = {
          PYTHONPATH = "${pkgs.python27Packages.graphite_web}/lib/python2.7/site-packages";
          DJANGO_SETTINGS_MODULE = "graphite.settings";
          GRAPHITE_CONF_DIR = configDir;
          GRAPHITE_STORAGE_DIR = dataDir;
        };
        serviceConfig = {
          ExecStart = ''
            ${pkgs.python27Packages.waitress}/bin/waitress-serve \
            --host=${cfg.web.host} --port=${toString cfg.web.port} \
            --call django.core.handlers.wsgi:WSGIHandler'';
          User = "graphite";
          Group = "graphite";
          PermissionsStartOnly = true;
        };
        preStart = ''
          if ! test -e ${dataDir}/db-created; then
            mkdir -p ${dataDir}/{whisper/,log/webapp/}
            chmod 0700 ${dataDir}/{whisper/,log/webapp/}

            # populate database
            ${pkgs.python27Packages.graphite_web}/bin/manage-graphite.py syncdb --noinput

            # create index
            ${pkgs.python27Packages.graphite_web}/bin/build-index.sh

            touch ${dataDir}/db-created

            chown -R graphite:graphite ${cfg.dataDir}
          fi
        '';
      };

      environment.systemPackages = [ pkgs.python27Packages.graphite_web ];
    })

    (mkIf cfg.api.enable {
      systemd.services.graphiteApi = {
        description = "Graphite Api Interface";
        wantedBy = [ "multi-user.target" ];
        after = [ "network-interfaces.target" ];
        environment = {
          PYTHONPATH =
            "${cfg.api.package}/lib/python2.7/site-packages:" +
            concatMapStringsSep ":" (f: f + "/lib/python2.7/site-packages") cfg.api.finders;
          GRAPHITE_API_CONFIG = graphiteApiConfig;
          LD_LIBRARY_PATH = "${pkgs.cairo}/lib";
        };
        serviceConfig = {
          ExecStart = ''
            ${pkgs.python27Packages.waitress}/bin/waitress-serve \
            --host=${cfg.api.host} --port=${toString cfg.api.port} \
            graphite_api.app:app
          '';
          User = "graphite";
          Group = "graphite";
          PermissionsStartOnly = true;
        };
        preStart = ''
          if ! test -e ${dataDir}/db-created; then
            mkdir -p ${dataDir}/cache/
            chmod 0700 ${dataDir}/cache/

            touch ${dataDir}/db-created

            chown -R graphite:graphite ${cfg.dataDir}
          fi
        '';
      };
    })

    (mkIf cfg.seyren.enable {
      systemd.services.seyren = {
        description = "Graphite Alerting Dashboard";
        wantedBy = [ "multi-user.target" ];
        after = [ "network-interfaces.target" "mongodb.service" ];
        environment = seyrenConfig;
        serviceConfig = {
          ExecStart = "${pkgs.seyren}/bin/seyren -httpPort ${toString cfg.seyren.port}";
          WorkingDirectory = dataDir;
          User = "graphite";
          Group = "graphite";
        };
        preStart = ''
          if ! test -e ${dataDir}/db-created; then
            mkdir -p ${dataDir}
            chown -R graphite:graphite ${dataDir}
          fi
        '';
      };

      services.mongodb.enable = mkDefault true;
    })

    (mkIf cfg.pager.enable {
      systemd.services.graphitePager = {
        description = "Graphite Pager Alerting Daemon";
        wantedBy = [ "multi-user.target" ];
        after = [ "network-interfaces.target" "redis.service" ];
        environment = {
          REDIS_URL = cfg.pager.redisUrl;
          GRAPHITE_URL = cfg.pager.graphiteUrl;
        };
        serviceConfig = {
          ExecStart = "${pkgs.pythonPackages.graphite_pager}/bin/graphite-pager --config ${pagerConfig}";
          User = "graphite";
          Group = "graphite";
        };
      };

      services.redis.enable = mkDefault true;

      environment.systemPackages = [ pkgs.pythonPackages.graphite_pager ];
    })

    (mkIf (
      cfg.carbon.enableCache || cfg.carbon.enableAggregator || cfg.carbon.enableRelay ||
      cfg.web.enable || cfg.api.enable ||
      cfg.seyren.enable || cfg.pager.enable
     ) {
      users.extraUsers = singleton {
        name = "graphite";
        uid = config.ids.uids.graphite;
        description = "Graphite daemon user";
        home = dataDir;
      };
      users.extraGroups.graphite.gid = config.ids.gids.graphite;
    })
  ];
}