module Support
  module Helpers
    class Image
      def initialize(image)
        @path = image
        @image = Magick::Image.read(image)[0]
      end

      def matches?(image_path_to_compare, max_difference: 0.05)
        difference_from(image_path_to_compare) < max_difference
      end

      # consider turning this into a custom matcher instead
      def should_match(image_path_to_compare, max_difference: 0.05)
        image_difference = difference_from(image_path_to_compare)
        fail(
          "Images don't match!\n"\
          "  Expected image: #{@path}\n"\
          "  Actual image: #{image_path_to_compare}\n"\
          "  Difference: #{image_difference}\n"\
          "  Threshold: #{max_difference}"
        ) unless image_difference < max_difference
      end

      private

      def difference_from(image_path)
        image_to_compare = Magick::Image.read(image_path)[0]

        assert_dimensions_match(image_to_compare)

        _, diff_metric = @image.compare_channel(image_to_compare, Magick::MeanSquaredErrorMetric)
        diff_metric
      end

      def assert_dimensions_match(other_image)
        base_dims = [@image.columns, @image.rows]
        compared_dims = [other_image.columns, other_image.rows]
        fail(
          "images do not match!\n"\
          "Base image: #{base_dims}\n"\
          "Compared image: #{compared_dims}"
        ) if base_dims != compared_dims
      end
    end
  end
end