1 files changed, 55 insertions, 0 deletions
diff --git a/app/services/zip_service.rb b/app/services/zip_service.rb
new file mode 100644
index 000000000..778bfd06d
--- /dev/null
+++ b/app/services/zip_service.rb
@@ -0,0 +1,55 @@
+class ZipService
+
+  attr_reader :current_entry, :zip_data
+
+  def initialize data
+    @zip_data = data
+    @current_entry = nil
+  end
+
+  class << self
+    def convert_entries entries
+      -> output_stream do
+        entries.each do |e|
+          output_stream.put_next_entry e.name
+          output_stream.write e.get_input_stream.read
+        end
+      end
+    end
+
+    def entries input_stream
+      Enumerator.new do |enum|
+        loop{ enum << input_stream.get_next_entry }
+      end.lazy.take_while{ |e| e }
+    end
+  end
+
+  def entry_groups
+    self.class.entries(input_stream).group_by(&method(:entry_key))
+  end
+
+  def entry_group_streams
+    entry_groups.map(&method(:make_stream)).to_h
+  end
+
+  def entry_key entry
+    entry.name.split('/', -1)[-2]
+  end
+
+  def make_stream pair
+    name, entries = pair 
+    [name,  make_stream_from( entries )]
+  end
+
+  def make_stream_from entries
+    Zip::OutputStream.write_buffer(&self.class.convert_entries(entries))
+  end
+
+  def next_entry
+    @current_entry = input_stream.get_next_entry
+  end
+
+  def input_stream
+    @__input_stream__ ||= Zip::InputStream.open(StringIO.new(zip_data))
+  end
+end