require "time"
require "socket"

module PlainApm
  module EventAttributes
    SOURCES_WITH_EXTRA_ATTRIBUTES = %w[
      action_controller
      action_mailer
      active_job
      exception
    ].freeze

    # FIXME: This is duplicated for ErrorReporter
    IGNORED_EXCEPTIONS = [
      "Sidekiq::JobRetry::Skip", # Sidekiq uses exceptions for control flow.
      "ActionController::RoutingError" # Rails unmapped route, raised before the request hits the app.
    ].freeze

    def attributes_from_exception(e, context, error_source)
      name = "exception"

      return [name, nil] if IGNORED_EXCEPTIONS.include?(e.class.name)

      attrs = context_attributes

      attrs[:class] = e.class.name
      attrs[:message] = e.message
      attrs[:backtrace] = e.backtrace

      attrs[:event_time] = now
      attrs[:event_utc_time] = utc_now

      if error_source
        attrs[:event_source] = error_source
      end

      if context[:controller]&.is_a?(ActionController::Base)
        attrs[:controller] = context[:controller].class.name
      end

      if context[:job]&.is_a?(ActiveJob::Base)
        attrs[:job_class] = context[:job].class.name
        attrs[:queue_name] = context[:job].queue_name
      end

      if context[:env]
        attrs[:params] = context.dig(:env, "action_dispatch.request.parameters")
        attrs[:action] = context.dig(:env, "action_dispatch.request.parameters", :action)
        attrs[:controller] = context.dig(:env, "action_controller.instance")&.class.name
      end

      # https://bugs.ruby-lang.org/issues/19197
      root_cause = e
      root_cause = root_cause.cause while root_cause.cause

      if root_cause != e
        attrs[:root_cause_class] = root_cause.class.name
        attrs[:root_cause_message] = root_cause.message
        attrs[:root_cause_backtrace] = root_cause.backtrace
        loc = source_location(root_cause.backtrace)
        if !loc.nil?
          attrs[:root_cause_location] = loc
        end
      end

      loc = source_location(e.backtrace)
      if !loc.nil?
        attrs[:source_location] = loc
      end

      add_trace_attributes(attrs)

      [name, attrs]
    end

    def attributes_from_notification(event)
      name, source = *event.name.split(".")
      loc = source_location

      attrs = context_attributes

      attrs[:source] = source
      attrs[:name] = name
      attrs[:allocations] = event.allocations
      attrs[:thread_cpu_time] = event.cpu_time
      attrs[:event_time] = event.time
      attrs[:duration] = event.duration

      if event.respond_to?(:utc_time)
        attrs[:event_utc_time] = event.utc_time
      end

      if event.respond_to?(:gc_time)
        attrs[:gc_time] = event.gc_time
      end

      if event.respond_to?(:gc_major_count)
        attrs[:gc_major_count] = event.gc_major_count
      end

      if event.respond_to?(:gc_minor_count)
        attrs[:gc_minor_count] = event.gc_minor_count
      end

      if event.respond_to?(:thread_allocations)
        attrs[:thread_allocations] = event.thread_allocations
      end

      if !loc.nil?
        attrs[:source_location] = loc
      end

      add_trace_attributes(attrs)

      [name, attrs]
    end

    private

    # TODO: There is a perf cost in Rubies for Process.pid until 3.3, so it
    # might be a good idea to cache this. See
    # https://bugs.ruby-lang.org/issues/19443 for the feature.
    def add_trace_attributes(attrs)
      attrs[:thread_id] = Thread.current.object_id
      attrs[:collected_at] = utc_now
      attrs[:pid] = Process.pid
      attrs[:version] = PlainApm::VERSION
      attrs[:hostname] = cached_attributes[:hostname]
      attrs[:revision] = cached_attributes[:revision]
    end

    def cached_attributes
      @cached_attributes ||= {
        hostname: Socket.gethostname,
        revision: PlainApm::DeployTracking.revision
      }
    end

    ##
    # Context contains the trace ID (which comes from either
    # HTTP_X_REQUEST_ID header, the deserialized job,
    # or is generated by the trace_id middleware).
    # It can also carry user inserted app data.
    def context_attributes
      if defined?(PlainApm::Extensions::Context)
        PlainApm::Extensions::Context.current.dup
      else
        {}
      end
    end

    def source_location(backtrace = nil)
      return if self.class.rails_root.nil?
      root_length = self.class.rails_root.length

      (backtrace || caller).each do |frame|
        if frame.start_with?(self.class.rails_root)
          path = frame[(root_length + 1)..-1]
          return path if path.start_with?("app") || path.start_with?("lib")
        end
      end

      nil
    end

    def now
      Process.clock_gettime(Process::CLOCK_MONOTONIC, :float_millisecond)
    end

    def utc_now
      Time.now.to_f
    end

    def self.included(other)
      other.class_eval do
        def self.rails_root
          return @rails_root if defined?(@rails_root)
          @rails_root = (defined?(Rails) && Rails.root.to_s.present?) ? Rails.root.to_s.freeze : nil
        end
      end
    end
  end
end