module Embedson
  module Model
    class EmbedsBuilder
      attr_reader :builder, :klass

      def initialize(builder)
        @builder = builder
        @klass = builder.klass
      end

      def define
        methods_embeds.each do |meth|
          klass.class_exec builder, &self.method(meth)
        end
      end

      private

      def methods_embeds
        [:writer, :reader, :related_model, :build_related_model, :send_to_related]
      end

      def writer(builder)
        klass.send :define_method, "#{builder.field_name}=" do |arg|
          send("#{builder.field_name}_verify_arg_klass", arg)
          send("#{builder.field_name}_send_to_related", arg)

          instance_variable_set(builder.instance_var_name, arg)
          val = arg.nil? ? arg : arg.to_h.stringify_keys
          unless val == read_attribute(builder.column_name)
            write_attribute(builder.column_name, val)
          end
        end
      end

      def reader(builder)
        klass.send :define_method, builder.field_name do
          return if read_attribute(builder.column_name).nil?

          send("#{builder.field_name}_build_related_model") if instance_variable_get(builder.instance_var_name).nil?
          instance_variable_get(builder.instance_var_name)
        end
      end

      def related_model(builder)
        klass.send :define_method, "#{builder.field_name}_related_model" do
          builder.related_klass_name.constantize.new(read_attribute(builder.column_name))
        end
        klass.send :private, "#{builder.field_name}_related_model"
      end

      def build_related_model(builder)
        klass.send :define_method, "#{builder.field_name}_build_related_model" do
          related_model = send("#{builder.field_name}_related_model")
          instance_variable_set(builder.instance_var_name, related_model)
          if related_model.respond_to?(builder.inverse_set)
            related_model.public_send(builder.inverse_set, self)
          end
        end
        klass.send :private, "#{builder.field_name}_build_related_model"
      end

      def send_to_related(builder)
        klass.send :define_method, "#{builder.field_name}_send_to_related" do |arg|
          if arg.respond_to?(builder.inverse_set) && arg.public_send(builder.inverse_get) != self
            arg.public_send(builder.inverse_set, self)
          end
        end
        klass.send :private, "#{builder.field_name}_send_to_related"
      end
    end
  end
end