# frozen_string_literal: true

module Datadog
  module Profiling
    module Collectors
      # Used to trigger the periodic execution of Collectors::ThreadState, which implements all of the sampling logic
      # itself; this class only implements the "when to do it" part.
      # Almost all of this class is implemented as native code.
      #
      # Methods prefixed with _native_ are implemented in `collectors_cpu_and_wall_time_worker.c`
      class CpuAndWallTimeWorker
        private

        attr_accessor :failure_exception

        public

        def initialize(
          gc_profiling_enabled:,
          no_signals_workaround_enabled:,
          thread_context_collector:,
          dynamic_sampling_rate_overhead_target_percentage:,
          allocation_profiling_enabled:,
          allocation_counting_enabled:,
          gvl_profiling_enabled:,
          # **NOTE**: This should only be used for testing; disabling the dynamic sampling rate will increase the
          # profiler overhead!
          dynamic_sampling_rate_enabled: true,
          skip_idle_samples_for_testing: false,
          idle_sampling_helper: IdleSamplingHelper.new
        )
          unless dynamic_sampling_rate_enabled
            Datadog.logger.warn(
              "Profiling dynamic sampling rate disabled. This should only be used for testing, and will increase overhead!"
            )
          end

          self.class._native_initialize(
            self_instance: self,
            thread_context_collector: thread_context_collector,
            gc_profiling_enabled: gc_profiling_enabled,
            idle_sampling_helper: idle_sampling_helper,
            no_signals_workaround_enabled: no_signals_workaround_enabled,
            dynamic_sampling_rate_enabled: dynamic_sampling_rate_enabled,
            dynamic_sampling_rate_overhead_target_percentage: dynamic_sampling_rate_overhead_target_percentage,
            allocation_profiling_enabled: allocation_profiling_enabled,
            allocation_counting_enabled: allocation_counting_enabled,
            gvl_profiling_enabled: gvl_profiling_enabled,
            skip_idle_samples_for_testing: skip_idle_samples_for_testing,
          )
          @worker_thread = nil
          @failure_exception = nil
          @start_stop_mutex = Mutex.new
          @idle_sampling_helper = idle_sampling_helper
          @wait_until_running_mutex = Mutex.new
          @wait_until_running_condition = ConditionVariable.new
        end

        def start(on_failure_proc: nil)
          @start_stop_mutex.synchronize do
            return if @worker_thread&.alive?

            Datadog.logger.debug { "Starting thread for: #{self}" }

            @idle_sampling_helper.start

            @worker_thread = Thread.new do
              Thread.current.name = self.class.name

              self.class._native_sampling_loop(self)

              Datadog.logger.debug("CpuAndWallTimeWorker thread stopping cleanly")
            rescue Exception => e # rubocop:disable Lint/RescueException
              @failure_exception = e
              Datadog.logger.warn(
                "CpuAndWallTimeWorker thread error. " \
                "Cause: #{e.class.name} #{e.message} Location: #{Array(e.backtrace).first}"
              )
              on_failure_proc&.call
            end
            @worker_thread.name = self.class.name # Repeated from above to make sure thread gets named asap
            @worker_thread.thread_variable_set(:fork_safe, true)
          end

          true
        end

        def stop
          @start_stop_mutex.synchronize do
            Datadog.logger.debug("Requesting CpuAndWallTimeWorker thread shut down")

            @idle_sampling_helper.stop

            return unless @worker_thread

            self.class._native_stop(self, @worker_thread)

            @worker_thread.join
            @worker_thread = nil
            @failure_exception = nil
          end
        end

        def reset_after_fork
          self.class._native_reset_after_fork(self)
        end

        def stats
          self.class._native_stats(self)
        end

        def stats_and_reset_not_thread_safe
          stats = self.stats
          self.class._native_stats_reset_not_thread_safe(self)
          stats
        end

        # Useful for testing, to e.g. make sure the profiler is running before we start running some code we want to observe
        def wait_until_running(timeout_seconds: 5)
          @wait_until_running_mutex.synchronize do
            return true if self.class._native_is_running?(self)

            @wait_until_running_condition.wait(@wait_until_running_mutex, timeout_seconds)

            if self.class._native_is_running?(self)
              true
            else
              raise "Timeout waiting for #{self.class.name} to start (waited for #{timeout_seconds} seconds)"
            end
          end
        end

        private

        def signal_running
          @wait_until_running_mutex.synchronize { @wait_until_running_condition.broadcast }
        end
      end
    end
  end
end