st0012/object_tracer

class ObjectTracer
  module Trackers
    class InitializationTracker < ObjectTracer
      def initialize(options = {}, &block)
        super
        event_type = @options[:event_type]
        # if a class doesn't override the 'initialize' method
        # Class.new will only trigger c_return or c_call
        @options[:event_type] = [event_type, "c_#{event_type}"]
      end

      def track(object)
        super
        @is_active_record_model = defined?(ActiveRecord) && target.ancestors.include?(ActiveRecord::Base)
        self
      end

      def build_payload(tp:, filepath:, line_number:)
        payload = super

        return payload if @is_active_record_model

        payload.return_value = payload.receiver
        payload.receiver = target
        payload
      end

      def validate_target!
        raise NotAClassError.new(target) unless target.is_a?(Class)
      end

      def filter_condition_satisfied?(tp)
        receiver = tp.self
        method_name = tp.callee_id

        if @is_active_record_model
          # ActiveRecord redefines model classes' .new method,
          # so instead of calling Model#initialize, it'll actually call Model.new
          # see https://github.com/rails/rails/blob/master/activerecord/lib/active_record/inheritance.rb#L50
          method_name == :new &&
            receiver.is_a?(Class) &&
            # this checks if the model class is the target class or a subclass of it
            receiver.ancestors.include?(target) &&
            # Model.new triggers both c_return and return events. so we should only return in 1 type of the events
            # otherwise the callback will be triggered twice
            tp.event == :return
        else
          method_name == :initialize && receiver.is_a?(target)
        end
      end
    end
  end
end