basic harness for extracting metadata

app/models/concerns/external_metadata_file_behavior.rb

@@ -37,4 +37,38 @@ def vector_file?
   def external_metadata_file?
     true
   end
+
+  # Extracts properties from the constitutent external metadata file
+  # @return [Hash]
+  def extract_metadata
+    fn = "extract_#{conforms_to.downcase}_metadata"
+    if respond_to?(fn.to_sym)
+      send(fn, metadata_xml)
+    else
+      fail "Unsupported metadata standard: #{conforms_to}"
+    end
+  end
+
+  # Retrives data from PCDM::File
+  def metadata_xml
+    Nokogiri::XML('<empty/>') # TODO: Get XML from file
+  end
+
+  def extract_iso19139_metadata(doc)
+    {
+      title: doc.at_xpath('//identificationInfo/MD_DataIdentification/citation/CI_Citation/title').text
+    }
+  end
+
+  def extract_fgdc_metadata(doc)
+    {
+      title: doc.at_xpath('//idinfo/citation/citeinfo/title').text
+    }
+  end
+
+  def extract_mods_metadata(doc)
+    {
+      title: doc.at_xpath('//titleInfo/title').text
+    }
+  end
 end

app/models/concerns/image_behavior.rb

@@ -82,4 +82,12 @@ def external_metadata_file?
   # def rasters_ids
   #   rasters.map(&:id)
   # end
+
+  # Extracts properties from the constitutent external metadata file
+  # @return [Hash]
+  # TODO: Does not support multiple external metadata files
+  def extract_metadata
+    return {} if metadata_files.blank?
+    metadata_files.first.extract_metadata
+  end
 end

app/models/concerns/raster_behavior.rb

@@ -60,4 +60,12 @@ def images
   def image
     images.first
   end
+
+  # Extracts properties from the constitutent external metadata file
+  # @return [Hash]
+  # TODO: Does not support multiple external metadata files
+  def extract_metadata
+    return {} if metadata_files.blank?
+    metadata_files.first.extract_metadata
+  end
 end

app/models/concerns/vector_behavior.rb

@@ -50,4 +50,12 @@ def external_metadata_file?
   def rasters
     aggregated_by.select { |parent| parent.class.included_modules.include?(::RasterBehavior) }
   end
+
+  # Extracts properties from the constitutent external metadata file
+  # @return [Hash]
+  # TODO: Does not support multiple external metadata files
+  def extract_metadata
+    return {} if metadata_files.blank?
+    metadata_files.first.extract_metadata
+  end
 end