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(span = nil)
  if span
    current_spans.delete(span)
  else
    span = current_spans.pop
  end
  return unless span
  span.done
  enqueue.call span
  update_span_metrics(span)
  span
end

def end_transaction(result = nil)
  return nil unless (transaction = current_transaction)
  self.current_transaction = nil
  transaction.done result
  if transaction.sampled? || @config.version < Config::ServerInfo::VERSION_8_0
    enqueue.call transaction
  end
  update_transaction_metrics(transaction)
  transaction
end

def handle_forking!
  stop
  start
end

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

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

def random_sample?(config)
  rand <= config.transaction_sample_rate
end

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

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

def set_user(user)
  return unless current_transaction
  current_transaction.set_user(user)
end

def start
  debug 'Starting instrumenter'
  # We call register! on @subscriber in case the
  # instrumenter was stopped and started again
  @subscriber&.register!
end

def start_span(
  name,
  type = nil,
  subtype: nil,
  action: nil,
  backtrace: nil,
  context: nil,
  trace_context: nil,
  parent: nil,
  sync: nil,
  exit_span: nil
)
  transaction =
    case parent
    when Span
      parent.transaction
    when Transaction
      parent
    else
      current_transaction
    end
  return unless transaction
  return unless transaction.sampled?
  return unless transaction.inc_started_spans!
  parent ||= (current_span || current_transaction)
  # To not mess with breakdown metric stats, exit spans MUST not add
  # sub-spans unless they share the same type and subtype.
  if parent && parent.is_a?(Span) && parent.exit_span?
    if parent.type != type || parent.subtype != subtype
      debug "Skipping new span '#{name}' as its parent is an exit_span"
      return
    end
  end
  span = Span.new(
    name: name,
    subtype: subtype,
    action: action,
    transaction: transaction,
    parent: parent,
    trace_context: trace_context,
    type: type,
    context: context,
    stacktrace_builder: stacktrace_builder,
    sync: sync,
    exit_span: exit_span
  )
  if backtrace && transaction.span_frames_min_duration
    span.original_backtrace = backtrace
  end
  current_spans.push span
  span.start
end

def start_transaction(
  name = nil,
  type = nil,
  config:,
  context: nil,
  trace_context: nil
)
  return nil unless config.instrument?
  if (transaction = current_transaction)
    raise ExistingTransactionError,
      "Transactions may not be nested.\n" \
      "Already inside #{transaction.inspect}"
  end
  if trace_context
    sampled = trace_context.recorded?
    sample_rate = trace_context.tracestate.sample_rate
  else
    sampled = random_sample?(config)
    sample_rate = sampled ? config.transaction_sample_rate : 0
  end
  transaction =
    Transaction.new(
      name,
      type,
      context: context,
      trace_context: trace_context,
      sampled: sampled,
      sample_rate: sample_rate,
      config: config
    )
  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!
end

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

def update_span_metrics(span)
  return unless span.transaction.collect_metrics?
  tags = {
    'span.type': span.type,
    'transaction.name': span.transaction.name,
    'transaction.type': span.transaction.type
  }
  tags[:'span.subtype'] = span.subtype if span.subtype
  @metrics.get(:breakdown).timer(
    :'span.self_time.sum.us',
    tags: tags, reset_on_collect: true
  ).update(span.self_time)
  @metrics.get(:breakdown).counter(
    :'span.self_time.count',
    tags: tags, reset_on_collect: true
  ).inc!
end

def update_transaction_metrics(transaction)
  return unless transaction.collect_metrics?
  tags = {
    'transaction.name': transaction.name,
    'transaction.type': transaction.type
  }
  return unless transaction.sampled?
  return unless transaction.breakdown_metrics
  span_tags = tags.merge('span.type': 'app')
  @metrics.get(:breakdown).timer(
    :'span.self_time.sum.us',
    tags: span_tags, reset_on_collect: true
  ).update(transaction.self_time)
  @metrics.get(:breakdown).counter(
    :'span.self_time.count',
    tags: span_tags, reset_on_collect: true
  ).inc!
end