require 'active_support/core_ext/string/inflections'

module UniverseCompiler
  module Entity

    module RelationsManagement

      def has_one(target_entity_type_or_class, name: nil, with_reverse_method: nil, unique: false)
        target_entity_type = normalize_entity_type target_entity_type_or_class
        field_name = relation_field_name name, target_entity_type
        define_constraint field_name, :has_one, target_entity_type
        return unless with_reverse_method

        define_constraint_for_reverse_method :has_one,
                                             target_entity_type,
                                             field_name,
                                             with_reverse_method,
                                             unique
      end

      def has_many(target_entity_type_or_class, name: nil, with_reverse_method: nil, unique: false)
        target_entity_type = normalize_entity_type target_entity_type_or_class
        field_name = relation_field_name name, target_entity_type
        field_name = field_name.to_s.pluralize.to_sym if name.nil?
        define_constraint field_name, :has_many, target_entity_type
        return unless with_reverse_method

        define_constraint_for_reverse_method :has_many,
                                             target_entity_type,
                                             field_name,
                                             with_reverse_method,
                                             unique
      end

      private

      def relation_field_name(name, target_entity_type)
        case name
        when NilClass
          target_entity_type
        when String, Symbol
          name.to_sym
        end
      end

      def define_constraint_for_reverse_method(relation_type, target_entity_type, source_field_name, with_reverse_method, unique)
        reverse_method_name = case with_reverse_method
                              when TrueClass
                                "referenced_from_#{self.entity_type}_#{source_field_name}".to_sym
                              when String, Symbol
                                with_reverse_method.to_sym
                              end
        target_class = UniverseCompiler::Entity::TypeManagement.type_class_mapping(target_entity_type)
        method_creation_data = {
            source_entity: self.entity_type,
            source_field: source_field_name,
            relation_type: relation_type,
            unique_result: unique
        }
        target_class.define_constraint reverse_method_name, :reverse_method, method_creation_data
        true
      end

    end

  end
end