# frozen_string_literal: true

module Datadog
  module Profiling
    # Responsible for wiring up the Profiler for execution
    module Component
      # Passing in a `nil` tracer is supported and will disable the following profiling features:
      # * Code Hotspots panel in the trace viewer, as well as scoping a profile down to a span
      # * Endpoint aggregation in the profiler UX, including normalization (resource per endpoint call)
      def self.build_profiler_component(settings:, agent_settings:, optional_tracer:) # rubocop:disable Metrics/MethodLength
        require_relative '../profiling/diagnostics/environment_logger'

        Profiling::Diagnostics::EnvironmentLogger.collect_and_log!

        return unless settings.profiling.enabled

        # Workaround for weird dependency direction: the Core::Configuration::Components class currently has a
        # dependency on individual products, in this case the Profiler.
        # (Note "currently": in the future we want to change this so core classes don't depend on specific products)
        #
        # If the current file included a `require 'datadog/profiler'` at its beginning, we would generate circular
        # requires when used from profiling:
        #
        # datadog/profiling
        #     └─requires─> datadog/core
        #                      └─requires─> datadog/core/configuration/components
        #                                       └─requires─> datadog/profiling       # Loop!
        #
        # ...thus in #1998 we removed such a require.
        #
        # On the other hand, if datadog/core is loaded by a different product and no general `require 'ddtrace'` is
        # done, then profiling may not be loaded, and thus to avoid this issue we do a require here (which is a
        # no-op if profiling is already loaded).
        require_relative '../profiling'
        return unless Profiling.supported?

        # Activate forking extensions
        Profiling::Tasks::Setup.new.run

        # NOTE: Please update the Initialization section of ProfilingDevelopment.md with any changes to this method

        no_signals_workaround_enabled = no_signals_workaround_enabled?(settings)
        timeline_enabled = settings.profiling.advanced.experimental_timeline_enabled
        allocation_profiling_enabled = enable_allocation_profiling?(settings)
        heap_sample_every = get_heap_sample_every(settings)
        heap_profiling_enabled = enable_heap_profiling?(settings, allocation_profiling_enabled, heap_sample_every)
        heap_size_profiling_enabled = enable_heap_size_profiling?(settings, heap_profiling_enabled)

        overhead_target_percentage = valid_overhead_target(settings.profiling.advanced.overhead_target_percentage)
        upload_period_seconds = [60, settings.profiling.advanced.upload_period_seconds].max

        recorder = Datadog::Profiling::StackRecorder.new(
          cpu_time_enabled: RUBY_PLATFORM.include?('linux'), # Only supported on Linux currently
          alloc_samples_enabled: allocation_profiling_enabled,
          heap_samples_enabled: heap_profiling_enabled,
          heap_size_enabled: heap_size_profiling_enabled,
          heap_sample_every: heap_sample_every,
          timeline_enabled: timeline_enabled,
        )
        thread_context_collector = build_thread_context_collector(settings, recorder, optional_tracer, timeline_enabled)
        worker = Datadog::Profiling::Collectors::CpuAndWallTimeWorker.new(
          gc_profiling_enabled: enable_gc_profiling?(settings),
          no_signals_workaround_enabled: no_signals_workaround_enabled,
          thread_context_collector: thread_context_collector,
          dynamic_sampling_rate_overhead_target_percentage: overhead_target_percentage,
          allocation_profiling_enabled: allocation_profiling_enabled,
        )

        internal_metadata = {
          no_signals_workaround_enabled: no_signals_workaround_enabled,
          timeline_enabled: timeline_enabled,
          heap_sample_every: heap_sample_every,
        }.freeze

        exporter = build_profiler_exporter(settings, recorder, internal_metadata: internal_metadata)
        transport = build_profiler_transport(settings, agent_settings)
        scheduler = Profiling::Scheduler.new(exporter: exporter, transport: transport, interval: upload_period_seconds)

        Profiling::Profiler.new(worker: worker, scheduler: scheduler)
      end

      private_class_method def self.build_thread_context_collector(settings, recorder, optional_tracer, timeline_enabled)
        Datadog::Profiling::Collectors::ThreadContext.new(
          recorder: recorder,
          max_frames: settings.profiling.advanced.max_frames,
          tracer: optional_tracer,
          endpoint_collection_enabled: settings.profiling.advanced.endpoint.collection.enabled,
          timeline_enabled: timeline_enabled,
        )
      end

      private_class_method def self.build_profiler_exporter(settings, recorder, internal_metadata:)
        code_provenance_collector =
          (Profiling::Collectors::CodeProvenance.new if settings.profiling.advanced.code_provenance_enabled)

        Profiling::Exporter.new(
          pprof_recorder: recorder,
          code_provenance_collector: code_provenance_collector,
          internal_metadata: internal_metadata,
        )
      end

      private_class_method def self.build_profiler_transport(settings, agent_settings)
        settings.profiling.exporter.transport ||
          Profiling::HttpTransport.new(
            agent_settings: agent_settings,
            site: settings.site,
            api_key: settings.api_key,
            upload_timeout_seconds: settings.profiling.upload.timeout_seconds,
          )
      end

      private_class_method def self.enable_gc_profiling?(settings)
        # See comments on the setting definition for more context on why it exists.
        if settings.profiling.advanced.force_enable_gc_profiling
          if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new('3')
            Datadog.logger.debug(
              'Profiling time/resources spent in Garbage Collection force enabled. Do not use Ractors in combination ' \
              'with this option as profiles will be incomplete.'
            )
          end

          true
        else
          false
        end
      end

      private_class_method def self.get_heap_sample_every(settings)
        heap_sample_rate = settings.profiling.advanced.experimental_heap_sample_rate

        raise ArgumentError, "Heap sample rate must be a positive integer. Was #{heap_sample_rate}" if heap_sample_rate <= 0

        heap_sample_rate
      end

      private_class_method def self.enable_allocation_profiling?(settings)
        unless settings.profiling.advanced.experimental_allocation_enabled
          # Allocation profiling disabled, short-circuit out
          return false
        end

        # Allocation sampling is safe and supported on Ruby 2.x, but has a few caveats on Ruby 3.x.

        # SEVERE - All configurations
        # Ruby 3.2.0 to 3.2.2 have a bug in the newobj tracepoint (https://bugs.ruby-lang.org/issues/19482,
        # https://github.com/ruby/ruby/pull/7464) that makes this crash in any configuration. This bug is
        # fixed on Ruby versions 3.2.3 and 3.3.0.
        if RUBY_VERSION.start_with?('3.2.') && RUBY_VERSION < '3.2.3'
          Datadog.logger.warn(
            'Allocation profiling is not supported in Ruby versions 3.2.0, 3.2.1 and 3.2.2 and will be forcibly '\
            'disabled. This is due to a VM bug that can lead to crashes (https://bugs.ruby-lang.org/issues/19482). '\
            'Other Ruby versions do not suffer from this issue.'
          )
          return false
        end

        # SEVERE - Only with Ractors
        # On Ruby versions 3.0 (all), 3.1.0 to 3.1.3, and 3.2.0 to 3.2.2 allocation profiling can trigger a VM bug
        # that causes a segmentation fault during garbage collection of Ractors
        # (https://bugs.ruby-lang.org/issues/18464). We don't recommend using this feature on such Rubies.
        # This bug is fixed on Ruby versions 3.1.4, 3.2.3 and 3.3.0.
        if RUBY_VERSION.start_with?('3.0.') ||
            (RUBY_VERSION.start_with?('3.1.') && RUBY_VERSION < '3.1.4') ||
            (RUBY_VERSION.start_with?('3.2.') && RUBY_VERSION < '3.2.3')
          Datadog.logger.warn(
            "Current Ruby version (#{RUBY_VERSION}) has a VM bug where enabling allocation profiling while using "\
            'Ractors may cause unexpected issues, including crashes (https://bugs.ruby-lang.org/issues/18464). '\
            'This does not happen if Ractors are not used.'
          )
        # ANNOYANCE - Only with Ractors
        # On all known versions of Ruby 3.x, due to https://bugs.ruby-lang.org/issues/19112, when a ractor gets
        # garbage collected, Ruby will disable all active tracepoints, which this feature internally relies on.
        elsif RUBY_VERSION.start_with?('3.')
          Datadog.logger.warn(
            'In all known versions of Ruby 3.x, using Ractors may result in allocation profiling unexpectedly ' \
            'stopping (https://bugs.ruby-lang.org/issues/19112). Note that this stop has no impact in your ' \
            'application stability or performance. This does not happen if Ractors are not used.'
          )
        end

        Datadog.logger.warn(
          'Enabled experimental allocation profiling. This is experimental, not recommended, and will increase overhead!'
        )

        true
      end

      private_class_method def self.enable_heap_profiling?(settings, allocation_profiling_enabled, heap_sample_rate)
        heap_profiling_enabled = settings.profiling.advanced.experimental_heap_enabled

        return false unless heap_profiling_enabled

        if RUBY_VERSION.start_with?('2.') && RUBY_VERSION < '2.7'
          Datadog.logger.warn(
            'Heap profiling currently relies on features introduced in Ruby 2.7 and will be forcibly disabled. '\
            'Please upgrade to Ruby >= 2.7 in order to use this feature.'
          )
          return false
        end

        if RUBY_VERSION < '3.1'
          Datadog.logger.debug(
            "Current Ruby version (#{RUBY_VERSION}) supports forced object recycling which has a bug that the " \
            'heap profiler is forced to work around to remain accurate. This workaround requires force-setting '\
            "the SEEN_OBJ_ID flag on objects that should have it but don't. Full details can be found in " \
            'https://github.com/DataDog/dd-trace-rb/pull/3360. This workaround should be safe but can be ' \
            'bypassed by disabling the heap profiler or upgrading to Ruby >= 3.1 where forced object recycling ' \
            'was completely removed (https://bugs.ruby-lang.org/issues/18290).'
          )
        end

        unless allocation_profiling_enabled
          raise ArgumentError,
            'Heap profiling requires allocation profiling to be enabled'
        end

        Datadog.logger.warn(
          "Enabled experimental heap profiling: heap_sample_rate=#{heap_sample_rate}. This is experimental, not " \
          'recommended, and will increase overhead!'
        )

        true
      end

      private_class_method def self.enable_heap_size_profiling?(settings, heap_profiling_enabled)
        heap_size_profiling_enabled = settings.profiling.advanced.experimental_heap_size_enabled

        return false unless heap_profiling_enabled && heap_size_profiling_enabled

        Datadog.logger.warn(
          'Enabled experimental heap size profiling. This is experimental, not recommended, and will increase overhead!'
        )

        true
      end

      private_class_method def self.no_signals_workaround_enabled?(settings) # rubocop:disable Metrics/MethodLength
        setting_value = settings.profiling.advanced.no_signals_workaround_enabled
        legacy_ruby_that_should_use_workaround = RUBY_VERSION.start_with?('2.3.', '2.4.', '2.5.')

        unless [true, false, :auto].include?(setting_value)
          Datadog.logger.error(
            "Ignoring invalid value for profiling no_signals_workaround_enabled setting: #{setting_value.inspect}. " \
            'Valid options are `true`, `false` or (default) `:auto`.'
          )

          setting_value = :auto
        end

        if setting_value == false
          if legacy_ruby_that_should_use_workaround
            Datadog.logger.warn(
              'The profiling "no signals" workaround has been disabled via configuration on a legacy Ruby version ' \
              '(< 2.6). This is not recommended ' \
              'in production environments, as due to limitations in Ruby APIs, we suspect it may lead to crashes ' \
              'in very rare situations. Please report any issues you run into to Datadog support or ' \
              'via <https://github.com/datadog/dd-trace-rb/issues/new>!'
            )
          else
            Datadog.logger.warn('Profiling "no signals" workaround disabled via configuration')
          end

          return false
        end

        if setting_value == true
          Datadog.logger.warn(
            'Profiling "no signals" workaround enabled via configuration. Profiling data will have lower quality.'
          )

          return true
        end

        # Setting is in auto mode. Let's probe to see if we should enable it:

        # We don't warn users in this situation because "upgrade your Ruby" is not a great warning
        return true if legacy_ruby_that_should_use_workaround

        if Gem.loaded_specs['mysql2'] && incompatible_libmysqlclient_version?(settings)
          Datadog.logger.warn(
            'Enabling the profiling "no signals" workaround because an incompatible version of the mysql2 gem is ' \
            'installed. Profiling data will have lower quality. ' \
            'To fix this, upgrade the libmysqlclient in your OS image to version 8.0.0 or above.'
          )
          return true
        end

        if Gem.loaded_specs['rugged']
          Datadog.logger.warn(
            'Enabling the profiling "no signals" workaround because the rugged gem is installed. ' \
            'This is needed because some operations on this gem are currently incompatible with the normal working mode ' \
            'of the profiler, as detailed in <https://github.com/datadog/dd-trace-rb/issues/2721>. ' \
            'Profiling data will have lower quality.'
          )
          return true
        end

        if (defined?(::PhusionPassenger) || Gem.loaded_specs['passenger']) && incompatible_passenger_version?
          Datadog.logger.warn(
            'Enabling the profiling "no signals" workaround because an incompatible version of the passenger gem is ' \
            'installed. Profiling data will have lower quality.' \
            'To fix this, upgrade the passenger gem to version 6.0.19 or above.'
          )
          return true
        end

        false
      end

      # Versions of libmysqlclient prior to 8.0.0 are known to have buggy handling of system call interruptions.
      # The profiler can sometimes cause system call interruptions, and so this combination can cause queries to fail.
      #
      # See https://bugs.mysql.com/bug.php?id=83109 and
      # https://docs.datadoghq.com/profiler/profiler_troubleshooting/ruby/#unexpected-run-time-failures-and-errors-from-ruby-gems-that-use-native-extensions-in-dd-trace-rb-1110
      # for details.
      #
      # The `mysql2` gem's `info` method can be used to determine which `libmysqlclient` version is in use, and thus to
      # detect if it's safe for the profiler to use signals or if we need to employ a fallback.
      private_class_method def self.incompatible_libmysqlclient_version?(settings)
        return true if settings.profiling.advanced.skip_mysql2_check

        Datadog.logger.debug(
          'Requiring `mysql2` to check if the `libmysqlclient` version it uses is compatible with profiling'
        )

        begin
          require 'mysql2'

          # The mysql2-aurora gem likes to monkey patch itself in replacement of Mysql2::Client, and uses
          # `method_missing` to delegate to the original BUT unfortunately does not implement `respond_to_missing?` and
          # thus our `respond_to?(:info)` below was failing.
          #
          # But on the bright side, the gem does stash a reference to the original Mysql2::Client class in a constant,
          # so if that constant exists, we use that for our probing.
          mysql2_client_class =
            if defined?(Mysql2::Aurora::ORIGINAL_CLIENT_CLASS)
              Mysql2::Aurora::ORIGINAL_CLIENT_CLASS
            elsif defined?(Mysql2::Client)
              Mysql2::Client
            end

          return true unless mysql2_client_class && mysql2_client_class.respond_to?(:info)

          info = mysql2_client_class.info
          libmysqlclient_version = Gem::Version.new(info[:version])

          compatible =
            libmysqlclient_version >= Gem::Version.new('8.0.0') ||
            looks_like_mariadb?(info, libmysqlclient_version)

          Datadog.logger.debug(
            "The `mysql2` gem is using #{compatible ? 'a compatible' : 'an incompatible'} version of " \
            "the `libmysqlclient` library (#{libmysqlclient_version})"
          )

          !compatible
        rescue StandardError, LoadError => e
          Datadog.logger.warn(
            'Failed to probe `mysql2` gem information. ' \
            "Cause: #{e.class.name} #{e.message} Location: #{Array(e.backtrace).first}"
          )

          true
        end
      end

      # See https://github.com/datadog/dd-trace-rb/issues/2976 for details.
      private_class_method def self.incompatible_passenger_version?
        if Gem.loaded_specs['passenger']
          Gem.loaded_specs['passenger'].version < Gem::Version.new('6.0.19')
        else
          true
        end
      end

      private_class_method def self.valid_overhead_target(overhead_target_percentage)
        if overhead_target_percentage > 0 && overhead_target_percentage <= 20
          overhead_target_percentage
        else
          Datadog.logger.error(
            'Ignoring invalid value for profiling overhead_target_percentage setting: ' \
            "#{overhead_target_percentage.inspect}. Falling back to default value."
          )

          2.0
        end
      end

      # To add just a bit more complexity to our detection code, in https://github.com/DataDog/dd-trace-rb/issues/3334
      # a user reported that our code was incorrectly flagging the mariadb variant of libmysqlclient as being
      # incompatible. In fact we have no reports of the mariadb variant needing the "no signals" workaround,
      # so we flag it as compatible when it's in use.
      #
      # A problem is that there doesn't seem to be an obvious way to query the mysql2 gem on which kind of
      # libmysqlclient it's using, so we detect it by looking at the version.
      #
      # The info method for mysql2 with mariadb looks something like this:
      # `{:id=>30308, :version=>"3.3.8", :header_version=>"11.2.2"}`
      #
      # * The version seems to come from https://github.com/mariadb-corporation/mariadb-connector-c and the latest
      # one is 3.x.
      # * The header_version is what people usually see as the "mariadb version"
      #
      # As a comparison, for libmysql the info looks like:
      # * `{:id=>80035, :version=>"8.0.35", :header_version=>"8.0.35"}`
      #
      # Thus our detection is version 4 or older, because libmysqlclient 4 is almost 20 years old so it's most probably
      # not that one + header_version being 10 or newer, since according to https://endoflife.date/mariadb that's a
      # sane range for modern mariadb releases.
      private_class_method def self.looks_like_mariadb?(info, libmysqlclient_version)
        header_version = Gem::Version.new(info[:header_version]) if info[:header_version]

        !!(header_version &&
          libmysqlclient_version < Gem::Version.new('5.0.0') &&
          header_version >= Gem::Version.new('10.0.0'))
      end
    end
  end
end