example middleware

Gemfile

@@ -23,7 +23,8 @@ gem 'psych', '< 4.0.0'
 
 gem 'adiwg-mdtranslator',
     git: 'https://github.com/GSA/mdTranslator.git',
-    branch: 'datagov'
+    # branch: 'feature/iso19115_3-reader'
+    branch: 'cleanup'
 
 # Use Active Storage variant
 # gem 'image_processing', '~> 1.2'

Gemfile.lock

@@ -1,7 +1,7 @@
 GIT
   remote: https://github.com/GSA/mdTranslator.git
-  revision: fe10f1d66171757f87be54e3053e0c09821500b4
-  branch: datagov
+  revision: 4a0bbb7ee5043ec4c6a9c2ef7e8d52af534de197
+  branch: cleanup
   specs:
     adiwg-mdtranslator (2.20.0.pre.beta.5)
       adiwg-mdcodes (= 2.10.0)

config/application.rb

@@ -17,6 +17,8 @@
 # require "sprockets/railtie"
 require 'rails/test_unit/railtie'
 
+require_relative '../lib/middleware/md_transformer'
+
 # Require the gems listed in Gemfile, including any gems
 # you've limited to :test, :development, or :production.
 Bundler.require(*Rails.groups)
@@ -26,6 +28,9 @@ class Application < Rails::Application
     # Initialize configuration defaults for originally generated Rails version.
     config.load_defaults 6.0
 
+    # intermediate transformation middleware
+    config.middleware.use MetadataTransformer
+
     # Settings in config/environments/* take precedence over those specified here.
     # Application configuration can go into files in config/initializers
     # -- all .rb files in that directory are automatically loaded after loading

lib/middleware/md_transformer.rb

@@ -0,0 +1,38 @@
+require 'nokogiri'
+
+class MetadataTransformer
+  def initialize(app)
+    @app = app
+  end
+
+  def determine_fgdc(xfgdc)
+    # FGDC CSDGM Version 2.0, 1998 ( FGDC-STD-001-1998)
+    # FGDC CSDGM Biological Data Profile (FGDC-STD-001.1-1999)
+    # FGDC CSDGM Metadata Profile for Shoreline Data (FGDC-STD-001.2-2001)
+    # FGDC Extension for Remote Sensing (FGDC-STD-012-2002)
+    # fgdc_standards = { 'FGDC-STD-001-1998' => 'version 2.0', 'FGDC-STD-001.1-1999' }
+    fgdc_standard_xpath = 'metainfo//metstdv'
+
+    standard = xfgdc.xpath(fgdc_standard_xpath)[0]
+  end
+
+  def determine_iso(x); end
+
+  def determine_schema(xml_str)
+    fgdc_root = 'metadata'
+    begin
+      xDoc = Nokogiri::XML(xml_str, &:strict)
+    rescue Nokogiri::XML::SyntaxError => e
+      'ERROR: XML file is not well formed'
+    end
+  end
+
+  def call(env)
+    request = Rack::Request.new(env)
+    file_param = request.params['file']
+    # transform
+    # request.update_param('file', transformed_file)
+
+    @app.call(env)
+  end
+end