# encoding: utf-8

require 'one_apm/support/collection_helper'
require 'one_apm/transaction/transaction_sample'
require 'one_apm/probe'
require 'one_apm/transaction'
module OneApm
  # a builder is created with every sampled transaction, to dynamically
  # generate the sampled data.  It is a thread-local object, and is not
  # accessed by any other thread so no need for synchronization.
  #
  # @api private
  class TransactionSampleBuilder

    # Once we hit the TT segment limit, we use this class to hold our place in
    # the tree so that we can still get accurate names and times on the
    # segments we've already created. The placeholder segment keeps a
    # depth counter that's incremented on each segment entry, and decremented
    # on exit, until it reaches zero, when we throw the placeholder away.
    # There should only ever be zero or one placeholder segment at a time.
    #
    # @api private
    class PlaceholderSegment
      attr_reader :parent_segment
      attr_accessor :depth

      def initialize(parent_segment)
        @parent_segment = parent_segment
        @depth = 1
      end

      # No-op - some clients expect to be able to use these to read/write
      # params on TT segments.
      def [](key); end
      def []=(key, value); end

      # Stubbed out in case clients try to touch params directly.
      def params; {}; end
      def params=; end
    end

    attr_reader :current_segment, :sample, :sample_start

    include OneApm::CollectionHelper

    def initialize(time=Time.now)
      @sample = OneApm::TransactionSample.new(time.to_f)
      @sample_start = time.to_f
      @current_segment = @sample.root_segment
    end

    def sample_id
      @sample.sample_id
    end

    def ignored?
      @ignore
    end

    def ignore_transaction
      @ignore = true
    end

    def segment_limit
      OneApm::Manager.config[:'transaction_tracer.limit_segments']
    end

    def trace_entry(time)
      if @sample.count_segments < segment_limit
        segment = @sample.create_segment(time.to_f - @sample_start)
        @current_segment.add_called_segment(segment)
        @current_segment = segment
        if @sample.count_segments == segment_limit()
          OneApm::Manager.logger.debug("Segment limit of #{segment_limit} reached, ceasing collection.")
        end
      else
        if @current_segment.is_a?(PlaceholderSegment)
          @current_segment.depth += 1
        else
          @current_segment = PlaceholderSegment.new(@current_segment)
        end
      end
      @current_segment
    end

    def trace_exit(metric_name, time)
      if @current_segment.is_a?(PlaceholderSegment)
        @current_segment.depth -= 1
        if @current_segment.depth == 0
          @current_segment = @current_segment.parent_segment
        end
      else
        @current_segment.metric_name = metric_name
        @current_segment.end_trace(time.to_f - @sample_start)
        @current_segment = @current_segment.parent_segment
      end
    end

    def finish_trace(time=Time.now.to_f, custom_params={})
      # Should never get called twice, but in a rare case that we can't
      # reproduce in house it does.  log forensics and return gracefully
      if @sample.finished
        OneApm::Manager.logger.error "Unexpected double-finish_trace of Transaction Trace Object: \n#{@sample.to_s}"
        return
      end
      @sample.root_segment.end_trace(time.to_f - @sample_start)
      @sample.params[:custom_params] ||= {}
      @sample.params[:custom_params].merge!(normalize_params(custom_params))

      # If we ever implement saving of TTs based on the record_tt flag on the
      # calling and called applications, we should change this flag's value.
      @sample.force_persist = false
      @sample.threshold = transaction_trace_threshold
      @sample.finished = true
      @current_segment = nil
    end

    OA_TT_THRESHOLD_KEY = :'transaction_tracer.transaction_threshold'

    def transaction_trace_threshold
      state = TransactionState.tl_get
      source_class = OneApm::Manager.config.source(OA_TT_THRESHOLD_KEY).class
      if source_class == Configuration::DefaultSource && state.current_transaction
        state.current_transaction.apdex_t * 4
      else
        OneApm::Manager.config[OA_TT_THRESHOLD_KEY]
      end
    end

    def scope_depth
      depth = -1        # have to account for the root
      current = @current_segment

      while(current)
        depth += 1
        current = current.parent_segment
      end

      depth
    end

    def set_transaction_uri(uri)
      @sample.params[:uri] ||= uri
    end

    def set_request_params(params)
      if OneApm::Manager.config[:capture_params]
        params = normalize_params(params)
        @sample.params[:request_params].merge!(params)
        @sample.params[:request_params].delete :controller
        @sample.params[:request_params].delete :action
      end
    end

    def set_transaction_name(name)
      @sample.transaction_name = name
    end

    def set_transaction_cpu_time(cpu_time)
      @sample.set_custom_param(:cpu_time, cpu_time)
    end

    def sample
      @sample
    end

  end
end