module LogStash; module Outputs; class ElasticSearch
  module Ilm

    ILM_POLICY_PATH = "default-ilm-policy.json"

    def setup_ilm
      logger.warn("Overwriting supplied index #{@index} with rollover alias #{@ilm_rollover_alias}") unless default_index?(@index)
      @index = @ilm_rollover_alias
      maybe_create_rollover_alias
      maybe_create_ilm_policy
    end

    def ilm_in_use?
      return @ilm_actually_enabled if defined?(@ilm_actually_enabled)
      @ilm_actually_enabled =
        begin
          if serverless?
            raise LogStash::ConfigurationError, "Invalid ILM configuration `ilm_enabled => true`. " +
              "Serverless Elasticsearch cluster does not support Index Lifecycle Management." if @ilm_enabled.to_s == 'true'
            @logger.info("ILM auto configuration (`ilm_enabled => auto` or unset) resolved to `false`. "\
              "Serverless Elasticsearch cluster does not support Index Lifecycle Management.") if @ilm_enabled == 'auto'
            false
          elsif @ilm_enabled == 'auto'
            if ilm_on_by_default?
              ilm_alias_set?
            else
              @logger.info("ILM auto configuration (`ilm_enabled => auto` or unset) resolved to `false`."\
                " Elasticsearch cluster is before 7.0.0, which is the minimum version required to automatically run Index Lifecycle Management")
              false
            end
          elsif @ilm_enabled.to_s == 'true'
            ilm_alias_set?
          else
            false
          end
        end
    end

    private

    def ilm_alias_set?
      default_index?(@index) || !default_rollover_alias?(@ilm_rollover_alias)
    end

    def ilm_on_by_default?
      maximum_seen_major_version >= 7
    end

    def default_index?(index)
      index == @default_index
    end

    def default_rollover_alias?(rollover_alias)
      rollover_alias == default_ilm_rollover_alias
    end

    def ilm_policy_default?
      ilm_policy == LogStash::Outputs::ElasticSearch::DEFAULT_POLICY
    end

    def maybe_create_ilm_policy
      if ilm_policy_default?
        client.ilm_policy_put(ilm_policy, policy_payload) unless client.ilm_policy_exists?(ilm_policy)
      else
        raise LogStash::ConfigurationError, "The specified ILM policy #{ilm_policy} does not exist on your Elasticsearch instance" unless client.ilm_policy_exists?(ilm_policy)
      end
    end

    def maybe_create_rollover_alias
      client.rollover_alias_put(rollover_alias_target, rollover_alias_payload) unless client.rollover_alias_exists?(ilm_rollover_alias)
    end

    def rollover_alias_target
      "<#{ilm_rollover_alias}-#{ilm_pattern}>"
    end

    def rollover_alias_payload
      {
          'aliases' => {
              ilm_rollover_alias =>{
                  'is_write_index' =>  true
              }
          }
      }
    end

    def policy_payload
      policy_path = ::File.expand_path(ILM_POLICY_PATH, ::File.dirname(__FILE__))
      LogStash::Json.load(::IO.read(policy_path))
    end
  end
end; end; end