class ElasticAPM::Instrumenter

def current_span
  current_spans.last
end

def current_spans
  @current.spans
end

def current_transaction
  @current.transaction
end

def current_transaction=(transaction)
  @current.transaction = transaction
end

def end_span
  return unless (span = current_spans.pop)
  span.done
  enqueue.call span
  span
end

def end_transaction(result = nil)
  return nil unless (transaction = current_transaction)
  self.current_transaction = nil
  transaction.done result
  enqueue.call transaction
  transaction
end

def initialize(config, stacktrace_builder:, &enqueue)
  @config = config
  @stacktrace_builder = stacktrace_builder
  @enqueue = enqueue
  @current = Current.new
end

def inspect
  '<ElasticAPM::Instrumenter ' \
    "current_transaction=#{current_transaction.inspect}" \
    '>'
end

def random_sample?
  rand <= config.transaction_sample_rate
end

def set_custom_context(context)
  return unless current_transaction
  current_transaction.context.custom.merge!(context)
end

def set_tag(key, value)
  return unless current_transaction
  key = key.to_s.gsub(/[\."\*]/, '_').to_sym
  current_transaction.context.tags[key] = value.to_s
end

def set_user(user)
  return unless current_transaction
  current_transaction.context.user = Context::User.infer(config, user)
end

def start
  debug 'Starting instrumenter'
end

def start_span(
  name,
  type = nil,
  backtrace: nil,
  context: nil,
  trace_context: nil
)
  return unless (transaction = current_transaction)
  return unless transaction.sampled?
  transaction.inc_started_spans!
  if transaction.max_spans_reached?(config)
    transaction.inc_dropped_spans!
    return
  end
  parent = current_span || transaction
  span = Span.new(
    name: name,
    transaction_id: transaction.id,
    trace_context: trace_context || parent.trace_context.child,
    type: type,
    context: context,
    stacktrace_builder: stacktrace_builder
  )
  if backtrace && config.span_frames_min_duration?
    span.original_backtrace = backtrace
  end
  current_spans.push span
  span.start
end

def start_transaction(
  name = nil,
  type = nil,
  context: nil,
  trace_context: nil
)
  return nil unless config.instrument?
  if (transaction = current_transaction)
    raise ExistingTransactionError,
      "Transactions may not be nested.\nAlready inside #{transaction}"
  end
  sampled = trace_context ? trace_context.recorded? : random_sample?
  transaction =
    Transaction.new(
      name,
      type,
      context: context,
      trace_context: trace_context,
      sampled: sampled,
      tags: config.default_tags
    )
  transaction.start
  self.current_transaction = transaction
end

def stop
  debug 'Stopping instrumenter'
  self.current_transaction = nil
  current_spans.pop until current_spans.empty?
  @subscriber.unregister! if @subscriber
end

def subscriber=(subscriber)
  debug 'Registering subscriber'
  @subscriber = subscriber
  @subscriber.register!
end