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require 'grpc'
require 'grpc/health/v1alpha/health_services'
require 'thread'

module Grpc
  # Health contains classes and modules that support providing a health check
  # service.
  module Health
    # Checker is implementation of the schema-specified health checking service.
    class Checker < V1alpha::Health::Service
      StatusCodes = GRPC::Core::StatusCodes
      HealthCheckResponse = V1alpha::HealthCheckResponse

      # Initializes the statuses of participating services
      def initialize
        @statuses = {}
        @status_mutex = Mutex.new  # guards access to @statuses
      end

      # Implements the rpc IDL API method
      def check(req, _call)
        status = nil
        @status_mutex.synchronize do
          status = @statuses["#{req.host}/#{req.service}"]
        end
        fail GRPC::BadStatus, StatusCodes::NOT_FOUND if status.nil?
        HealthCheckResponse.new(status: status)
      end

      # Adds the health status for a given host and service.
      def add_status(host, service, status)
        @status_mutex.synchronize { @statuses["#{host}/#{service}"] = status }
      end

      # Clears the status for the given host or service.
      def clear_status(host, service)
        @status_mutex.synchronize { @statuses.delete("#{host}/#{service}") }
      end

      # Clears alls the statuses.
      def clear_all
        @status_mutex.synchronize { @statuses = {} }
      end
    end
  end
end
