houdini/app/models/concerns/image/attachment_extensions.rb

module Image::AttachmentExtensions
    extend ActiveSupport::Concern
    class_methods do
        def has_one_attached_with_sizes(attribute_name, sizes)
            if sizes.nil? || !sizes.is_a?(Hash) || !sizes.any?
                raise ArgumentError, "You must pass a valid hash of sizes"
            end
            attribute = attribute_name.to_s

            # clean up sizes
            sizes.keys.each do |key|
                value = sizes[key]
                if value.is_a?(Numeric)
                    sizes[key] = [value, value]
                elsif value.is_a?(Array) && value.count == 1 && value.all?{|i| i.is_a?(Numeric)}
                    sizes[key]= [value[0], value[0]]
                elsif value.is_a?(Array) && value.count == 2 && value.all?{|i| i.is_a?(Numeric)}
                    sizes[key] = [value[0], value[1]]
                else 
                    raise ArgumentError, "#{value.to_s} was not a valid size."
                end
            end

            class_eval <<-RUBY, __FILE__, __LINE__ + 1
                def #{attribute}_by_size(size)
                     case (size)
                    #{sizes.map do |k,v| 
                        <<-INNER
                        when :#{k.to_sym}
                            return #{attribute}.variant(resize: "#{v[0]}x#{v[1]}")
                        INNER
                    end.join("\n")}
                     else
                        raise ArgumentError, ":" + size.to_s + " is not a valid size. Valid sizes are: #{sizes.keys.map{|i| ":" + i.to_s}.join(', ')}"
                     end
                end
             RUBY
        end

        def has_one_attached_with_default(attribute_name, default_path, **options)
            after_save do
                attribute = send(attribute_name)
                unless attribute.attached?
                    attribute.attach(io: File.open(default_path), **options)
                end
                self
            end
        end
    end
end