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# license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright
# ownership. Elasticsearch B.V. licenses this file to you under
# the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#  http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.

require "logstash/api/commands/base"
require 'logstash/util/thread_dump'
require 'logstash/config/pipelines_info'
require_relative "hot_threads_reporter"

java_import java.nio.file.Files
java_import java.nio.file.Paths

module LogStash
  module Api
    module Commands
      class Stats < Commands::Base
        def queue
          pipeline_ids = service.get_shallow(:stats, :pipelines).keys
          total_queued_events = 0
          pipeline_ids.each do |pipeline_id|
            p_stats = service.get_shallow(:stats, :pipelines, pipeline_id.to_sym)
            type = p_stats.dig(:queue, :type)&.value
            pipeline = service.agent.get_pipeline(pipeline_id)
            next if pipeline.nil? || pipeline.system? || type != 'persisted'
            total_queued_events += p_stats.dig(:queue, :events)&.value || 0
          end

          {:events_count => total_queued_events}
        rescue LogStash::Instrument::MetricStore::MetricNotFound
          {}
        end

        def jvm
          {
            :threads => extract_metrics(
              [:jvm, :threads],
              :count,
              :peak_count
            ),
            :mem => memory,
            :gc => gc,
            :uptime_in_millis => service.get_shallow(:jvm, :uptime_in_millis),
          }
        end

        def reloads
          service.get_shallow(:stats, :reloads)
        end

        def process
          extract_metrics(
            [:jvm, :process],
            :open_file_descriptors,
            :peak_open_file_descriptors,
            :max_file_descriptors,
            [:mem, [:total_virtual_in_bytes]],
            [:cpu, [:total_in_millis, :percent, :load_average]]
          )
        end

        def events
          extract_metrics(
            [:stats, :events],
            :in, :filtered, :out, :duration_in_millis, :queue_push_duration_in_millis
          )
        rescue LogStash::Instrument::MetricStore::MetricNotFound
          # if the stats/events metrics have not yet been populated, return an empty map
          {}
        end

        def flow
          extract_metrics(
            [:stats, :flow],
            :input_throughput, :filter_throughput, :output_throughput, :queue_backpressure, :worker_concurrency
          )
        rescue LogStash::Instrument::MetricStore::MetricNotFound
          # if the stats/events metrics have not yet been populated, return an empty map
          {}
        end

        def pipeline(pipeline_id = nil, opts = {})
          extended_stats = LogStash::Config::PipelinesInfo.format_pipelines_info(
            service.agent,
            service.snapshot.metric_store,
            true).each_with_object({}) do |pipeline_stats, memo|
              p_id = pipeline_stats["id"].to_s
              memo[p_id] = pipeline_stats
            end

          if pipeline_id.nil?
            pipeline_ids = service.get_shallow(:stats, :pipelines).keys
            pipeline_ids.each_with_object({}) do |pipeline_id, result|
              extended_pipeline = extended_stats[pipeline_id.to_s]
              result[pipeline_id] = plugins_stats_report(pipeline_id, extended_pipeline, opts)
            end
          else
            extended_pipeline = extended_stats[pipeline_id.to_s]
            { pipeline_id => plugins_stats_report(pipeline_id, extended_pipeline, opts) }
          end
        rescue # failed to find pipeline
          {}
        end

        def memory
          memory = service.get_shallow(:jvm, :memory)
          {
            :heap_used_percent => memory[:heap][:used_percent],
            :heap_committed_in_bytes => memory[:heap][:committed_in_bytes],
            :heap_max_in_bytes => memory[:heap][:max_in_bytes],
            :heap_used_in_bytes => memory[:heap][:used_in_bytes],
            :non_heap_used_in_bytes => memory[:non_heap][:used_in_bytes],
            :non_heap_committed_in_bytes => memory[:non_heap][:committed_in_bytes],
            :pools => memory[:pools].inject({}) do |acc, (type, hash)|
              hash.delete("committed_in_bytes")
              acc[type] = hash
              acc
            end
          }
        end

        def os
          service.get_shallow(:os)
        rescue
          # The only currently fetch OS information is about the linux
          # containers.
          {}
        end

        def gc
          service.get_shallow(:jvm, :gc)
        end

        def hot_threads(options = {})
          HotThreadsReport.new(self, options)
        end

        def geoip
          service.get_shallow(:geoip_download_manager)
        rescue
          {}
        end

        private
        def plugins_stats_report(pipeline_id, extended_pipeline, opts = {})
          stats = service.get_shallow(:stats, :pipelines, pipeline_id.to_sym)
          PluginsStats.report(stats, extended_pipeline, opts)
        end

        module PluginsStats
          module_function

          def plugin_stats(stats, plugin_type)
            # Turn the `plugins` stats hash into an array of [ {}, {}, ... ]
            # This is to produce an array of data points, one point for each
            # plugin instance.
            return [] unless stats[:plugins] && stats[:plugins].include?(plugin_type)
            stats[:plugins][plugin_type].collect do |id, data|
              { :id => id }.merge(data)
            end
          end

          def refine_batch_metrics(stats)
            # current is a tuple of [event_count, byte_size] store the reference locally to avoid repeatedly
            # reading and retrieve unrelated values
            current_data_point = stats[:batch][:current]
# FlowMetric (from stats[:batch][:event_count][:average]) returns a composite object containing lifetime/last_1_minute/etc values. In order to get the map of sub-metrics we must use `.value`.
# See: https://github.com/elastic/logstash/blob/279171b79c1f3be5fc85e6e2e4092281e504a6f9/logstash-core/src/main/java/org/logstash/instrument/metrics/ExtendedFlowMetric.java#L89
            event_count_average_flow_metric = stats[:batch][:event_count][:average].value
            event_count_average_lifetime = event_count_average_flow_metric["lifetime"] ? event_count_average_flow_metric["lifetime"].round : 0
            byte_size_average_flow_metric = stats[:batch][:byte_size][:average].value
            byte_size_average_lifetime = byte_size_average_flow_metric["lifetime"] ? byte_size_average_flow_metric["lifetime"].round : 0
            result = {
              :event_count => {
                # current_data_point is an instance of org.logstash.instrument.metrics.gauge.LazyDelegatingGauge so need to invoke getValue() to obtain the actual value
                :current => current_data_point.value[0],
                :average => {
                  :lifetime => event_count_average_lifetime
                }
              },
              :byte_size => {
                :current => current_data_point.value[1],
                :average => {
                  :lifetime => byte_size_average_lifetime
                }
              }
            }
            # Enrich byte_size and event_count averages with the last 1, 5, 15 minutes averages if available
            [:last_1_minute, :last_5_minutes, :last_15_minutes].each do |window|
              key = window.to_s
              result[:event_count][:average][window] = event_count_average_flow_metric[key]&.round if event_count_average_flow_metric[key]
              result[:byte_size][:average][window] = byte_size_average_flow_metric[key]&.round if byte_size_average_flow_metric[key]
            end

            if stats[:batch][:byte_size][:batch_structure_metric]
              byte_size_histogram = stats[:batch][:byte_size][:batch_structure_metric]
              # stats[:batch][:byte_size][:batch_structure_metric] is an instance of org.logstash.instrument.metrics.BatchStructureMetric
              # so need to call "value" to grab the map of sub-metrics which contains the histogram percentiles
              # as org.logstash.instrument.metrics.BatchStructureMetric$HistogramMetricData
              [:last_1_minute, :last_5_minutes, :last_15_minutes, :lifetime].each do |window|
                byte_size_histogram_value = byte_size_histogram.value
                if byte_size_histogram_value[window.to_s]
                  reshape_histogram_percentiles_for_window(:byte_size, byte_size_histogram_value, window, result)
                  result[:byte_size][:max] ||= {}
                  result[:byte_size][:max][window] = byte_size_histogram_value[window.to_s].max_value.round
                end
              end
            end
            if stats[:batch][:event_count][:batch_structure_metric]
              event_count_histogram = stats[:batch][:event_count][:batch_structure_metric]
              [:last_1_minute, :last_5_minutes, :last_15_minutes].each do |window|
                event_count_histogram_value = event_count_histogram.value
                if event_count_histogram_value[window.to_s]
                  reshape_histogram_percentiles_for_window(:event_count, event_count_histogram_value, window, result)
                end
              end
            end
            result
          end
          private :refine_batch_metrics

          def reshape_histogram_percentiles_for_window(target_field, histogram_metric, window, result)
            result[target_field][:p50] = {} if result[target_field][:p50].nil?
            result[target_field][:p90] = {} if result[target_field][:p90].nil?

            histogram_data = histogram_metric[window.to_s]
            result[target_field][:p50][window] = histogram_data.get50Percentile.round
            result[target_field][:p90][window] = histogram_data.get90Percentile.round
          end
          private :reshape_histogram_percentiles_for_window

          def report(stats, extended_stats = nil, opts = {})
            ret = {
              :events => stats[:events],
              :flow => stats[:flow],
              :plugins => {
                :inputs => plugin_stats(stats, :inputs),
                :codecs => plugin_stats(stats, :codecs),
                :filters => plugin_stats(stats, :filters),
                :outputs => plugin_stats(stats, :outputs)
              },
              :reloads => stats[:reloads],
              :queue => stats[:queue],
              :pipeline => {
                :workers => stats.dig(:config, :workers),
                :batch_size => stats.dig(:config, :batch_size),
                :batch_delay => stats.dig(:config, :batch_delay),
              }
            }
            ret[:batch] = refine_batch_metrics(stats) if stats.include?(:batch)
            ret[:dead_letter_queue] = stats[:dlq] if stats.include?(:dlq)

            # if extended_stats were provided, enrich the return value
            if extended_stats
              ret[:queue].merge!(extended_stats["queue"]) if extended_stats.include?("queue")
              ret[:hash] = extended_stats["hash"]
              ret[:ephemeral_id] = extended_stats["ephemeral_id"]
              if opts[:vertices] && extended_stats.include?("vertices")
                ret[:vertices] = extended_stats["vertices"].map { |vertex| decorate_vertex(vertex) }
              end
            end

            ret
          end

          ##
          # Returns a vertex, decorated with additional metadata if available.
          # Does not mutate the passed `vertex` object.
          # @api private
          # @param vertex [Hash{String=>Object}]
          # @return [Hash{String=>Object}]
          def decorate_vertex(vertex)
            plugin_id = vertex[:id]&.to_s
            return vertex unless plugin_id && LogStash::PluginMetadata.exists?(plugin_id)

            plugin_metadata = LogStash::PluginMetadata.for_plugin(plugin_id)
            cluster_uuid = plugin_metadata&.get(:cluster_uuid)
            vertex = vertex.merge("cluster_uuid" => cluster_uuid) unless cluster_uuid.nil?

            vertex
          end
        end # module PluginsStats
      end
    end
  end
end
