[dev] add a data_loader alternative to input_loader

lib/refrepo/data_loader.rb

+# Load a hierarchy of JSON file into a Ruby hash
+
+require 'refrepo/hash/hash'
+
+def load_data_hierarchy
+
+  global_hash = {} # the global data structure
+
+  directory = File.expand_path("../../data/grid5000/", File.dirname(__FILE__))
+  Dir.chdir(directory) do
+
+    # Recursively list the .yaml files.
+    # The order in which the results are returned depends on the system (http://ruby-doc.org/core-2.2.3/Dir.html).
+    # => List deepest files first as they have lowest priority when hash keys are duplicated.
+    list_of_files = Dir['**/*.json'].sort_by { |x| -x.count('/') }
+
+    list_of_files.each do |filename|
+      # Load JSON
+      file_hash = JSON::parse(IO::read(filename))
+
+      # Inject the file content into the global_hash, at the right place
+      path_hierarchy = File.dirname(filename).split('/')     # Split the file path (path relative to input/)
+      path_hierarchy = [] if path_hierarchy == ['.']
+
+      if ['nodes', 'network_equipments'].include?(path_hierarchy.last)
+        # it's a node or a network_equipment, add the uid
+        path_hierarchy << file_hash['uid']
+      end
+      file_hash = Hash.from_array(path_hierarchy, file_hash) # Build the nested hash hierarchy according to the file path
+      global_hash = global_hash.deep_merge(file_hash)        # Merge global_hash and file_hash. The value for entries with duplicate keys will be that of file_hash
+
+      # Expand the hash. Done at each iteration for enforcing priorities between duplicate entries:
+      # ie. keys to be expanded have lowest priority on existing entries but higher priority on the entries found in the next files
+      global_hash.expand_square_brackets(file_hash)
+
+    end
+
+  end
+
+  return global_hash
+end