gistfile1.rb

class ProductImageCollection

  def initialize(images)
    self.images = load_images(images)
  end

  def images_for(group: nil, color: nil, size: nil)
    processor = ProductImageCollectionProcessor.new(images.clone)
    processor.filter(group, color)
    processor.resize(size) if size.present?
    processor.images
  end

private

  def load_images(images)
    images.map{|img| ProductImage.new(img) }
  end

  attr_accessor :images

  class ProductImageCollectionProcessor

    attr_reader :images

    def initialize(images)
      self.images = images
    end

    def filter(group, color)
      filter_by_group(group) if group.present?
      filter_by_color(color) if color.present?
    end

    def resize(size)
      images.map!{|img| img.resize_to(size) }
    end

  private

    attr_writer :images

    def filter_by_group(group)
      images.select! do |image|
        image.path =~ /\/#{group}\//
      end
    end

    def filter_by_color(color)
      images.select! do |image|
        image.name =~ /#{color}/
      end
    end

  end
end