obstools/healthcheck-endpoint

# frozen_string_literal: true

module OnStrum
  module Healthcheck
    class Configuration
      ATTRIBUTES = %i[
        services
        services_startup
        services_liveness
        services_readiness
        endpoints_namespace
        endpoint_startup
        endpoint_liveness
        endpoint_readiness
        endpoint_startup_status_success
        endpoint_liveness_status_success
        endpoint_readiness_status_success
        endpoint_startup_status_failure
        endpoint_liveness_status_failure
        endpoint_readiness_status_failure
      ].freeze
      ENDPOINTS_NAMESPACE = '/healthcheck'
      ENDPOINT_STARTUP = '/startup'
      ENDPOINT_LIVENESS = '/liveness'
      ENDPOINT_READINESS = '/readiness'
      DEFAULT_HTTP_STATUS_SUCCESS = 200
      DEFAULT_HTTP_STATUS_FAILURE = 500
      AVILABLE_HTTP_STATUSES_SUCCESS = (DEFAULT_HTTP_STATUS_SUCCESS..226).freeze
      AVILABLE_HTTP_STATUSES_FAILURE = (DEFAULT_HTTP_STATUS_FAILURE..511).freeze

      Settings = ::Struct.new(*OnStrum::Healthcheck::Configuration::ATTRIBUTES, keyword_init: true) do
        def update(&block)
          return self unless block

          tap(&block)
        end
      end

      attr_reader(*OnStrum::Healthcheck::Configuration::ATTRIBUTES)

      def initialize(&block)
        configuration_settings = build_configuration_settings(&block)
        OnStrum::Healthcheck::Configuration::ATTRIBUTES.each do |attribute|
          public_send(:"#{attribute}=", configuration_settings.public_send(attribute))
        end
      end

      OnStrum::Healthcheck::Configuration::ATTRIBUTES.each do |attribute|
        define_method(:"#{attribute}=") do |argument|
          validate_attribute(__method__, attribute, argument)
          instance_variable_set(:"@#{attribute}", argument)
        end
      end

      private

      def build_configuration_settings(&block) # rubocop:disable Metrics/MethodLength
        OnStrum::Healthcheck::Configuration::Settings.new(
          services: {},
          services_startup: [],
          services_liveness: [],
          services_readiness: [],
          endpoints_namespace: OnStrum::Healthcheck::Configuration::ENDPOINTS_NAMESPACE,
          endpoint_startup: OnStrum::Healthcheck::Configuration::ENDPOINT_STARTUP,
          endpoint_liveness: OnStrum::Healthcheck::Configuration::ENDPOINT_LIVENESS,
          endpoint_readiness: OnStrum::Healthcheck::Configuration::ENDPOINT_READINESS,
          endpoint_startup_status_success: OnStrum::Healthcheck::Configuration::DEFAULT_HTTP_STATUS_SUCCESS,
          endpoint_liveness_status_success: OnStrum::Healthcheck::Configuration::DEFAULT_HTTP_STATUS_SUCCESS,
          endpoint_readiness_status_success: OnStrum::Healthcheck::Configuration::DEFAULT_HTTP_STATUS_SUCCESS,
          endpoint_startup_status_failure: OnStrum::Healthcheck::Configuration::DEFAULT_HTTP_STATUS_FAILURE,
          endpoint_liveness_status_failure: OnStrum::Healthcheck::Configuration::DEFAULT_HTTP_STATUS_FAILURE,
          endpoint_readiness_status_failure: OnStrum::Healthcheck::Configuration::DEFAULT_HTTP_STATUS_FAILURE
        ).update(&block)
      end

      def validate_attribute(method, attribute, value) # rubocop:disable Metrics/AbcSize
        raise_unless(OnStrum::Healthcheck::Error::Configuration::ArgumentType, method, *validator_argument_type(attribute, value))
        case attribute
        when OnStrum::Healthcheck::Configuration::ATTRIBUTES[0]
          raise_unless(OnStrum::Healthcheck::Error::Configuration::NotCallableService, method, *validator_services_callable(value))
        when *OnStrum::Healthcheck::Configuration::ATTRIBUTES[1..3]
          raise_unless(OnStrum::Healthcheck::Error::Configuration::UnknownService, method, *validator_services_conformity(value))
        when *OnStrum::Healthcheck::Configuration::ATTRIBUTES[4..7]
          raise_unless(OnStrum::Healthcheck::Error::Configuration::EnpointPattern, method, *validator_endpoint(value))
        when *OnStrum::Healthcheck::Configuration::ATTRIBUTES[8..10]
          raise_unless(OnStrum::Healthcheck::Error::Configuration::HttpStatusSuccess, method, *validator_http_status_success(value))
        when *OnStrum::Healthcheck::Configuration::ATTRIBUTES[11..13]
          raise_unless(OnStrum::Healthcheck::Error::Configuration::HttpStatusFailure, method, *validator_http_status_failure(value))
        end
      end

      def validator_argument_type(method_name, argument)
        [
          argument,
          argument.is_a?(
            case method_name
            when :services then ::Hash
            when *OnStrum::Healthcheck::Configuration::ATTRIBUTES[1..3] then ::Array
            when *OnStrum::Healthcheck::Configuration::ATTRIBUTES[4..7] then ::String
            when *OnStrum::Healthcheck::Configuration::ATTRIBUTES[8..13] then ::Integer
            end
          )
        ]
      end

      def validator_endpoint(argument)
        [argument, argument[%r{\A/.*\z}]]
      end

      def validator_http_status_success(argument)
        [argument, OnStrum::Healthcheck::Configuration::AVILABLE_HTTP_STATUSES_SUCCESS.include?(argument)]
      end

      def validator_http_status_failure(argument)
        [argument, OnStrum::Healthcheck::Configuration::AVILABLE_HTTP_STATUSES_FAILURE.include?(argument)]
      end

      def validator_services_callable(services_to_check, target_service = nil)
        result = services_to_check.all? do |service_name, service_context|
          target_service = service_name
          service_context.respond_to?(:call)
        end

        [target_service, result]
      end

      def validator_services_conformity(services_to_check, target_service = nil)
        result = services_to_check.all? do |service_name|
          target_service = service_name
          services.key?(service_name)
        end

        [target_service, result]
      end

      def raise_unless(exception_class, argument_name, argument_context, condition)
        raise exception_class.new(argument_context, argument_name) unless condition
      end
    end
  end
end