# frozen_string_literal: true

require "faraday"
require "faraday_middleware"
require "rufus/scheduler"

require_relative "../sampler/rules_sampler"
require_relative "../sampler/message_process_sampler"

module Aspecto
  # Aspecto's OpenTelemetry distribution
  module OpenTelemetry
    module Config
      # Handle fetching of remote configuration from aspecto
      class RemoteConfig
        def initialize(aspecto_auth, service_name, env, fallback_sampler)
          @service_name = service_name
          @env = env
          @fallback_sampler = fallback_sampler

          aspecto_config_url = ENV.fetch("ASPECTO_CONFIG_HOST", "https://config.aspecto.io")
          @http_client = Faraday.new "#{aspecto_config_url}/config/#{aspecto_auth}" do |f|
            f.response :json # decode response bodies as JSON
          end
          @http_client.options.timeout = 10

          @scheduler = Rufus::Scheduler.new
          @remote_config_poll_frequency = ENV.fetch("ASPECTO_REMOTE_CONFIG_POLL_FREQUENCY", "30s")
          @scheduler.interval @remote_config_poll_frequency, first: :now do
            update_config
          end

          ::OpenTelemetry.logger.info "[Aspecto] SDK client initialized"
        end

        def shutdown
          @scheduler.shutdown
        end

        private

        def update_config # rubocop:disable Metrics/AbcSize
          ::OpenTelemetry::Common::Utilities.untraced do
            response = @http_client.get do |req|
              req.headers["If-None-Match"] = @latest_config_etag unless @latest_config_etag.nil?
            end
            @latest_config_etag = response.headers["etag"]
            return if response.status == 304

            if response.status >= 400
              ::OpenTelemetry.logger.error("[Aspecto] error when trying to get remote config. will try again in #{@remote_config_poll_frequency}")
              return
            end
            handle_new_config response.body if response.status < 300
          end
        rescue StandardError => e
          ::OpenTelemetry.logger.error "[Aspecto] updating remote config failed. using previous remote config"
          ::OpenTelemetry.logger.debug e
        end

        def handle_new_config(config)
          ::OpenTelemetry.logger.info("[Aspecto] successfully received remote configuration")
          update_sampler config["samplingRules"]
        end

        def update_sampler(sampler_config)
          rules_sampler = Sampler::RulesSampler.new sampler_config, @fallback_sampler, @service_name, @env
          service_sampler = ::OpenTelemetry::SDK::Trace::Samplers.parent_based(root: rules_sampler)
          message_process_sampler = Sampler::MessageProcessSampler.new rules_sampler, service_sampler
          # updating the sampler should be thread safe as it's an atomic setter on a global value
          ::OpenTelemetry.tracer_provider.sampler = message_process_sampler
        end
      end
    end
  end
end