gonzalo-bulnes/kata-images_gallery_generator

require 'libxml'

require 'images_gallery/models/collection'
require 'images_gallery/models/image'

module ImagesGallery
  module Models
    class Source

      include LibXML
      include XML::SaxParser::Callbacks

      attr_reader :images

      # Provides a collection of images to presenters
      #
      # Extracts some images attributes from an XML collection of works
      # and collects the images as plain Ruby objects so other classes
      # can use them with presentational purpose.
      #
      # This class should be able to parse efficiently large XML files.
      #
      # file - Path to an XML representation of the images (metadata, EXIF)
      #
      # Example:
      #
      #     source = ImagesGallery::Source.new('path/to/source.xml')
      #     source.parse   # creates a Collection of Images
      #     source.images  # is available after parsing
      #
      # Returns a Source object, ready to parse the corresponding XML file.
      def initialize(file)
        @file = XML::SaxParser.file(file)
        @file.callbacks = self
      end

      def parse
        @images = Models::Collection.new
        begin
          @file.parse
        rescue LibXML::XML::Error
          raise SourceFileInvalidError
        end
      end

      # Callbacks can't be private, yet they are not part of the public API.

      def on_start_element(element, attributes)
        @current_element = element

        if element == 'work'
          @current_image = Models::Image.new
        end

        if element == 'url' && attributes['type'] == 'small'
          @current_element = 'thumbnail URL'
        end
      end

      def on_end_element(element)
        if element == 'work'
          @images << @current_image
        end

        if element == 'id'
          @current_image.id = @current_id
        end

        if element == 'iso_speed_ratings'
          @current_image.iso = @current_iso
        end

        if element == 'make'
          @current_image.make = @current_make
        end

        if element == 'model'
          @current_image.model = @current_model
        end

        if @current_element == 'thumbnail URL'
          @current_image.src = @current_src
        end

        @current_element = nil
      end

      def on_characters(char)
        if @current_element == 'id'
          @current_id = char
        end

        if @current_element == 'iso_speed_ratings'
          @current_iso = char
        end

        if @current_element == 'make'
          @current_make = char
        end

        if @current_element == 'model'
          @current_model = char
        end

        if @current_element == 'thumbnail URL'
          @current_src = char
        end
      end

      def on_end_document
        @current_element = nil
      end
    end
  end
end