ama-team / ruby-entity-mapper

require_relative '../../mixin/reflection'

require_relative '../../mixin/errors'

module AMA

  module Entity

    class Mapper

      module Handler

        module Attribute

          # Default validator for single attribute

          class Validator

            INSTANCE = new

            # @param [Object] value Attribute value

            # @param [AMA::Entity::Mapper::Type::Attribute] attribute

            # @param [AMA::Entity::Mapper::Context] _context

            # @return [Array<String>] Single violation, list of violations

            def validate(value, attribute, _context)

              violation = validate_internal(value, attribute)

              violation.nil? ? [] : [violation]

            end

            private

            def validate_internal(value, attribute)

              if illegal_nil?(value, attribute)

                return "Attribute #{attribute} could not be nil"

              end

              if invalid_type?(value, attribute)

                return "Provided value doesn't conform to " \

                  "any of attribute #{attribute} types (#{attribute.types})"

              end

              return unless illegal_value?(value, attribute)

              "Provided value doesn't match default value (#{value})" \

                " or any of allowed values (#{attribute.values})"

            end

            # @param [Object] value Attribute value

            # @param [AMA::Entity::Mapper::Type::Attribute] attribute

            # @return [TrueClass, FalseClass]

            def illegal_nil?(value, attribute)

              return false unless value.nil? && !attribute.nullable

              attribute.types.none? { |type| type.instance?(value) }

            end

            # @param [Object] value Attribute value

            # @param [AMA::Entity::Mapper::Type::Attribute] attribute

            # @return [TrueClass, FalseClass]

            def invalid_type?(value, attribute)

              attribute.types.all? do |type|

                !type.respond_to?(:instance?) || !type.instance?(value)

              end

            end

            # @param [Object] value Attribute value

            # @param [AMA::Entity::Mapper::Type::Attribute] attribute

            # @return [TrueClass, FalseClass]

            class << self

              include Mixin::Reflection

              # @param [Validator] validator

              # @return [Validator]

                handler = handler_factory(validator, INSTANCE)

                description = "Safety wrapper for #{validator}"

                wrapper = method_object(:validate, to_s: description, &handler)

                wrapper.singleton_class.instance_eval do

                  include Mixin::Errors

                end

                wrapper

              end

              private

              # @param [Validator] validator

              # @param [Validator] fallback

              # @return [Proc]

              def handler_factory(validator, fallback)

                lambda do |val, attr, ctx|

                  begin

                    validator.validate(val, attr, ctx) do |v, a, c|

                      fallback.validate(v, a, c)

                    end

                  rescue StandardError => e

                    raise_if_internal(e)

                    message = "Unexpected error from validator #{validator}"

                    signature = '(value, attribute, context)'

                    options = { parent: e, context: ctx, signature: signature }

                    compliance_error(message, **options)

                  end

                end

              end

            end

          end

        end

      end

    end

  end

end