require 'dry/core/inflector'
require 'dry/core/cache'
require 'dry/core/class_builder'

require 'rom/struct'
require 'rom/schema/type'

module ROM
  class Repository
    # @api private
    class StructBuilder
      extend Dry::Core::Cache

      def call(*args)
        fetch_or_store(*args) do
          name, header = args
          attributes = visit(header).compact

          build_class(name, ROM::Struct) do |klass|
            attributes.each do |(name, type)|
              klass.attribute(name, type)
            end
          end
        end
      end
      alias_method :[], :call

      private

      def visit(ast)
        name, node = ast
        __send__("visit_#{name}", node)
      end

      def visit_header(node)
        node.map(&method(:visit))
      end

      def visit_relation(node)
        relation_name, meta, header = node
        name = meta[:combine_name] || relation_name.relation

        model = call(name, header)

        if meta[:combine_type] == :many
          [name, Types::Array.member(model)]
        else
          [name, model.optional]
        end
      end

      def visit_attribute(attr)
        [attr.aliased? && !attr.wrapped? ? attr.alias : attr.name, attr.type]
      end

      def build_class(name, parent, &block)
        Dry::Core::ClassBuilder.new(name: class_name(name), parent: parent).call(&block)
      end

      def class_name(name)
        "ROM::Struct[#{Dry::Core::Inflector.classify(Dry::Core::Inflector.singularize(name))}]"
      end
    end
  end
end