module Skylight
  module Test
    module Mocking
      def mock!(config_opts = {}, &callback)
        config_opts[:mock_submission] ||= callback || proc {}

        config_class =
          Class.new(Config) do
            def validate_with_server
              true
            end
          end

        config = config_class.load(config_opts)
        config[:authentication] ||= "zomg"

        class_eval do
          unless const_defined?(:OriginalInstrumenter)
            const_set :OriginalInstrumenter, Instrumenter
            remove_const :Instrumenter
            const_set(
              :Instrumenter,
              Class.new(OriginalInstrumenter) do
                def self.name
                  "Mocked Instrumenter"
                end

                def native_start
                  true
                end

                def native_submit_trace(trace)
                  config[:mock_submission].call(trace)
                end

                def native_stop
                end
              end
            )

            const_set :OriginalTrace, Trace
            remove_const :Trace
            const_set(
              :Trace,
              Class.new(OriginalTrace) do
                def self.native_new(start, _uuid, endpoint, meta)
                  inst = super
                  inst.instance_variable_set(:@start, start)
                  inst.instance_variable_set(:@endpoint, endpoint)
                  inst.instance_variable_set(:@starting_endpoint, endpoint)
                  inst.instance_variable_set(:@meta, meta)
                  inst
                end

                attr_reader :endpoint, :starting_endpoint, :meta

                def mock_spans
                  @mock_spans ||= []
                end

                def filter_spans
                  if block_given?
                    mock_spans.select { |span| yield span }
                  else
                    mock_spans.reject { |span| span[:cat] == "noise.gc" }
                  end
                end

                def native_get_uuid
                  @uuid
                end

                def uuid=(value)
                  @uuid = value
                end

                def native_get_started_at
                  @start
                end

                def native_set_endpoint(endpoint)
                  @endpoint = endpoint
                end

                def native_set_component(component)
                  @component = component
                end

                def native_start_span(time, cat)
                  span = { start: time, cat: cat }
                  mock_spans << span

                  # Return integer like the native method does
                  mock_spans.index(span)
                end

                def native_span_set_title(span, title)
                  mock_spans[span][:title] = title
                end

                def native_span_set_description(span, desc)
                  mock_spans[span][:desc] = desc
                end

                def native_span_set_meta(span, meta)
                  mock_spans[span][:meta] = meta
                end

                def native_span_started(span)
                end

                def native_span_set_exception(span, exception_object, exception)
                  mock_spans[span][:exception_object] = exception_object
                  mock_spans[span][:exception] = exception
                end

                def native_stop_span(span, time)
                  span = mock_spans[span]
                  span[:duration] = time - span[:start]
                  nil
                end

                def native_use_pruning
                  @using_native_pruning = true
                end
              end
            )
          end
        end

        start!(config)
      end

      def unmock!
        if const_defined?(:OriginalInstrumenter)
          class_eval do
            remove_const :Instrumenter
            const_set :Instrumenter, OriginalInstrumenter
            remove_const :OriginalInstrumenter

            remove_const :Trace
            const_set :Trace, OriginalTrace
            remove_const :OriginalTrace
          end
        end
      end
    end
  end
end