# encoding: utf-8

require 'monitor'

class OneApm::Collector::TransactionEventAggregator
  include OneApm::Coerce, MonitorMixin

  # The type field of the sample
  SAMPLE_TYPE                    = 'Transaction'.freeze

  # Strings for static keys of the sample structure
  TYPE_KEY                       = 'type'.freeze
  TIMESTAMP_KEY                  = 'timestamp'.freeze
  NAME_KEY                       = 'name'.freeze
  DURATION_KEY                   = 'duration'.freeze
  HTTP_RESPONSE_CODE_KEY         = 'httpResponseCode'.freeze
  GUID_KEY                       = 'bw.guid'.freeze
  REFERRING_TRANSACTION_GUID_KEY = 'bw.referringTransactionGuid'.freeze
  CAT_TRIP_ID_KEY                = 'bw.tripId'.freeze
  CAT_PATH_HASH_KEY              = 'bw.pathHash'.freeze
  CAT_REFERRING_PATH_HASH_KEY    = 'bw.referringPathHash'.freeze
  CAT_ALTERNATE_PATH_HASHES_KEY  = 'bw.alternatePathHashes'.freeze
  APDEX_PERF_ZONE_KEY            = 'bw.apdexPerfZone'.freeze
  SYNTHETICS_RESOURCE_ID_KEY     = "bw.syntheticsResourceId".freeze
  SYNTHETICS_JOB_ID_KEY          = "bw.syntheticsJobId".freeze
  SYNTHETICS_MONITOR_ID_KEY      = "bw.syntheticsMonitorId".freeze

  def initialize(event_listener)
    super()

    @enabled       = false
    @notified_full = false

    @samples            = ::OneApm::Agent::SampledBuffer.new(OneApm::Manager.config[:'analytics_events.max_samples_stored'])
    @synthetics_samples = ::OneApm::Agent::SyntheticsEventBuffer.new(OneApm::Manager.config[:'synthetics.events_limit'])

    event_listener.subscribe(:transaction_finished, &method(:on_transaction_finished))
    self.register_config_callbacks
  end

  # Fetch a copy of the sampler's gathered samples. (Synchronized)
  def samples
    self.synchronize { @samples.to_a.concat(@synthetics_samples.to_a) }
  end

  def reset!
    sample_count, request_count, synthetics_dropped = 0
    old_samples = nil

    self.synchronize do
      sample_count = @samples.size
      request_count = @samples.num_seen

      synthetics_dropped = @synthetics_samples.num_dropped

      old_samples = @samples.to_a + @synthetics_samples.to_a
      @samples.reset!
      @synthetics_samples.reset!

      @notified_full = false
    end

    [old_samples, sample_count, request_count, synthetics_dropped]
  end

  # Clear any existing samples, reset the last sample time, and return the
  # previous set of samples. (Synchronized)
  def harvest!
    old_samples, sample_count, request_count, synthetics_dropped = reset!
    record_sampling_rate(request_count, sample_count) if @enabled
    record_dropped_synthetics(synthetics_dropped)
    old_samples
  end

  # Merge samples back into the buffer, for example after a failed
  # transmission to the collector. (Synchronized)
  def merge!(old_samples)
    self.synchronize do
      old_samples.each { |s| append_event(s) }
    end
  end

  def record_sampling_rate(request_count, sample_count)
    request_count_lifetime = @samples.seen_lifetime
    sample_count_lifetime = @samples.captured_lifetime
    OneApm::Manager.logger.debug("Sampled %d / %d (%.1f %%) requests this cycle, %d / %d (%.1f %%) since startup" % [
      sample_count,
      request_count,
      (sample_count.to_f / request_count * 100.0),
      sample_count_lifetime,
      request_count_lifetime,
      (sample_count_lifetime.to_f / request_count_lifetime * 100.0)
    ])

    engine = OneApm::Manager.agent.stats_engine
    engine.tl_record_supportability_metric_count("TransactionEventAggregator/requests", request_count)
    engine.tl_record_supportability_metric_count("TransactionEventAggregator/samples", sample_count)
  end

  def record_dropped_synthetics(synthetics_dropped)
    return unless synthetics_dropped > 0

    OneApm::Manager.logger.debug("Synthetics transaction event limit (#{@samples.capacity}) reached. Further synthetics events this harvest period dropped.")

    engine = OneApm::Manager.agent.stats_engine
    engine.tl_record_supportability_metric_count("TransactionEventAggregator/synthetics_events_dropped", synthetics_dropped)
  end

  def register_config_callbacks
    OneApm::Manager.config.register_callback(:'analytics_events.max_samples_stored') do |max_samples|
      OneApm::Manager.logger.debug "TransactionEventAggregator max_samples set to #{max_samples}"
      self.synchronize { @samples.capacity = max_samples }
    end

    OneApm::Manager.config.register_callback(:'synthetics.events_limit') do |max_samples|
      OneApm::Manager.logger.debug "TransactionEventAggregator limit for synthetics events set to #{max_samples}"
      self.synchronize { @synthetics_samples.capacity = max_samples }
    end

    OneApm::Manager.config.register_callback(:'analytics_events.enabled') do |enabled|
      @enabled = enabled
    end
  end

  def notify_full
    OneApm::Manager.logger.debug "Transaction event capacity of #{@samples.capacity} reached, beginning sampling"
    @notified_full = true
  end

  # Event handler for the :transaction_finished event.
  def on_transaction_finished(payload)
    return unless @enabled

    main_event = create_main_event(payload)
    custom_params = create_custom_parameters(payload)

    self.synchronize { append_event([main_event, custom_params]) }
    notify_full if !@notified_full && @samples.full?
  end

  def append_event(event)
    main_event, _ = event

    if main_event.include?(SYNTHETICS_RESOURCE_ID_KEY)
      # Try adding to synthetics buffer. If anything is rejected, give it a
      # shot in the main transaction events (where it may get sampled)
      result, rejected = @synthetics_samples.append_with_reject(event)

      if rejected
        @samples.append(rejected)
      end
    else
      @samples.append(event)
    end
  end

  def self.map_metric(metric_name, to_add={})
    to_add.values.each(&:freeze)

    mappings = OVERVIEW_SPECS.fetch(metric_name, {})
    mappings.merge!(to_add)

    OVERVIEW_SPECS[metric_name] = mappings
  end

  OVERVIEW_SPECS = {}

  # All Transactions
  # Don't need to use the transaction-type specific metrics since this is
  # scoped to just one transaction, so Datastore/all has what we want.
  map_metric('Datastore/all',         :total_call_time => "databaseDuration")
  map_metric('Datastore/all',         :call_count      => "databaseCallCount")
  map_metric('GC/Transaction/all',    :total_call_time => "gcCumulative")

  # Web Metrics
  map_metric('WebFrontend/QueueTime', :total_call_time => "queueDuration")
  map_metric('Memcache/allWeb',       :total_call_time => "memcacheDuration")

  map_metric('External/allWeb',       :total_call_time => "externalDuration")
  map_metric('External/allWeb',       :call_count      => "externalCallCount")

  # Background Metrics
  map_metric('Memcache/allOther',     :total_call_time => "memcacheDuration")

  map_metric('External/allOther',     :total_call_time => "externalDuration")
  map_metric('External/allOther',     :call_count      => "externalCallCount")

  def append_metrics(txn_metrics, sample)
    if txn_metrics
      OVERVIEW_SPECS.each do |(name, extracted_values)|
        if txn_metrics.has_key?(name)
          stat = txn_metrics[name]
          extracted_values.each do |value_name, key_name|
            sample[key_name] = stat.send(value_name)
          end
        end
      end
    end
  end

  def create_main_event(payload)
    sample = {
      TIMESTAMP_KEY => float(payload[:start_timestamp]),
      NAME_KEY      => string(payload[:name]),
      DURATION_KEY  => float(payload[:duration]),
      TYPE_KEY      => SAMPLE_TYPE,
    }
    append_metrics(payload[:metrics], sample)
    optionally_append(GUID_KEY,                       :guid, sample, payload)
    optionally_append(REFERRING_TRANSACTION_GUID_KEY, :referring_transaction_guid, sample, payload)
    optionally_append(CAT_TRIP_ID_KEY,                :cat_trip_id, sample, payload)
    optionally_append(CAT_PATH_HASH_KEY,              :cat_path_hash, sample, payload)
    optionally_append(CAT_REFERRING_PATH_HASH_KEY,    :cat_referring_path_hash, sample, payload)
    optionally_append(APDEX_PERF_ZONE_KEY,            :apdex_perf_zone, sample, payload)
    optionally_append(SYNTHETICS_RESOURCE_ID_KEY,     :synthetics_resource_id, sample, payload)
    optionally_append(SYNTHETICS_JOB_ID_KEY,          :synthetics_job_id, sample, payload)
    optionally_append(SYNTHETICS_MONITOR_ID_KEY,      :synthetics_monitor_id, sample, payload)
    append_http_response_code(sample, payload)
    append_cat_alternate_path_hashes(sample, payload)
    sample
  end

  def append_http_response_code(sample, payload)
    unless OneApm::Manager.config[:disable_rack_middleware]
      optionally_append(HTTP_RESPONSE_CODE_KEY, :http_response_code, sample, payload)
    end
  end

  def append_cat_alternate_path_hashes(sample, payload)
    if payload.include?(:cat_alternate_path_hashes)
      sample[CAT_ALTERNATE_PATH_HASHES_KEY] = payload[:cat_alternate_path_hashes].sort.join(',')
    end
  end

  def optionally_append(sample_key, payload_key, sample, payload)
    if payload.include?(payload_key)
      sample[sample_key] = string(payload[payload_key])
    end
  end

  def create_custom_parameters(payload)
    custom_params = {}
    if OneApm::Manager.config[:'analytics_events.capture_attributes']
      custom_params.merge!(event_params(payload[:custom_params] || {}))
    end
    custom_params
  end

end