class Analyzer

# File lib/controller/analyzer.rb, line 11
def initialize(base_image, new_image)
  raise 'The images need to be in png format' unless are_images_png?(base_image, new_image)
  self.images = [
      ChunkyPNG::Image.from_file(base_image),
      ChunkyPNG::Image.from_file(new_image),
  ]
  raise_different_size unless images_have_same_width?
  self.difference = difference_analyzer
  self.difference_in_percent = percent_calculator(difference)
end

# File lib/controller/analyzer.rb, line 22
def save_output(path)
  @output.save(path)
end

# File lib/controller/analyzer.rb, line 30
def are_images_png?(base, new)
  true if (base.downcase.include? 'png') && (new.downcase.include? 'png')
end

# File lib/controller/analyzer.rb, line 42
def difference_analyzer
  @output = ChunkyPNG::Image.new(images.first.width, images.first.height, WHITE)
  difference = []
  images.first.height.times do |y|
    images.first.row(y).each_with_index do |pixel, x|
      begin
        unless pixel == images.last[x,y]
          score = Math.sqrt(
              (r(images.last[x,y]) - r(pixel)) ** 2 +
              (g(images.last[x,y]) - g(pixel)) ** 2 +
              (b(images.last[x,y]) - b(pixel)) ** 2
          ) / Math.sqrt(MAX ** 2 * 3)

          @output[x,y] = grayscale(MAX - (score * MAX).round)
          difference << score
        end
      rescue ChunkyPNG::OutOfBounds
        # "out of bound error"
        # in Y-Direction (= one image is longer than the other)
        # if webpages change, they may have a different vertical length
      end
    end
  end
  difference
end

# File lib/controller/analyzer.rb, line 34
def images_have_same_width?
  images.first.width == images.last.width
end

# File lib/controller/analyzer.rb, line 68
def percent_calculator(difference)
  if difference == []
    0
  else
    ((difference.inject {|sum, value| sum + value} / images.first.pixels.length) * 100).to_f
  end
end

# File lib/controller/analyzer.rb, line 38
def raise_different_size
  raise "The images do not have the same width."
end