# frozen_string_literal: true

require "rufus/scheduler"
require "net/http"
require "json"

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
          @error_reported = false
          @got_remote_config = false
          @fallback_sampler = fallback_sampler
          aspecto_config_host = ENV.fetch("ASPECTO_CONFIG_HOST", "https://config.aspecto.io")
          @aspecto_config_url = URI("#{aspecto_config_host}/config/#{aspecto_auth}")
          init_http_client

          @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] initialized remote config polling"
        rescue StandardError => e
          ::OpenTelemetry.logger.error "[Aspecto] failed to initialize remote config polling"
          ::OpenTelemetry.logger.error e
        end

        def shutdown
          @scheduler.shutdown
        end

        private

        def init_http_client
          write_timeout_supported = Gem::Version.new(RUBY_VERSION) >= Gem::Version.new("2.6")

          @http_client = Net::HTTP.new(@aspecto_config_url.host, @aspecto_config_url.port)
          @http_client.read_timeout = 10
          @http_client.open_timeout = 10
          @http_client.write_timeout = 10 if write_timeout_supported
          @http_client.max_retries = 0

          # use uri.scheme == 'https' instead
          @http_client.use_ssl = true
          @http_client.verify_mode = OpenSSL::SSL::VERIFY_PEER
        end

        def update_config
          ::OpenTelemetry::Common::Utilities.untraced do
            request = Net::HTTP::Get.new(@aspecto_config_url.path)
            request["If-None-Match"] = @latest_config_etag unless @latest_config_etag.nil?
            response = @http_client.request(request)
            response_code = response.code.to_i

            return if response_code == 304

            if response_code >= 400
              log_config_error "failed to get remote config with http response #{response_code}."
              return
            end

            @latest_config_etag = response["etag"]
            handle_new_config JSON.parse(response.body) if response_code < 300
          end
        rescue StandardError => e
          log_config_error "updating remote config failed with exception.", e
        end

        def handle_new_config(config)
          update_sampler config["samplingRules"]
          @error_reported = false
          @got_remote_config = true
          ::OpenTelemetry.logger.info("[Aspecto] successfully updated remote configuration")
        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

        def log_config_error(msg, err = nil)
          return if @error_reported # report every issue only once

          retry_msg = "will try again until success every #{@remote_config_poll_frequency}."
          previous_config_msg = @got_remote_config ? "using previous remote config" : "no previous config is avialable"
          ::OpenTelemetry.logger.info("[Aspecto]: #{msg} #{retry_msg} #{previous_config_msg}")
          ::OpenTelemetry.logger.info(err) if err
          @error_reported = true
        end
      end
    end
  end
end