[32] allow access to header

inspired from #73 but stripped down to just the header to see if that might be more amenable to get in.

Also because of the TODO note in the update function, only supports reading these files, not updating them.

Author: Ian Norris

lib/docx/document.rb

@@ -22,7 +22,7 @@ module Docx
   class Document
     include Docx::SimpleInspect
 
-    attr_reader :xml, :doc, :zip, :styles
+    attr_reader :xml, :doc, :zip, :styles, :headers
 
     def initialize(path_or_io, options = {})
       @replace = {}
@@ -40,6 +40,7 @@ def initialize(path_or_io, options = {})
       @document_xml = document.get_input_stream.read
       @doc = Nokogiri::XML(@document_xml)
       load_styles
+      load_headers
       yield(self) if block_given?
     ensure
       @zip.close unless @zip.nil?
@@ -200,6 +201,15 @@ def with_zip64_disabled
       Zip.write_zip64_support = previous
     end
 
+    def load_headers
+      header_files = @zip.glob("word/header*.xml").map{|h| h.name}
+      filename_and_contents_pairs = header_files.map do |file|
+        simple_file_name = file.sub(/^word\//, "").sub(/\.xml$/, "")
+        [simple_file_name, Nokogiri::XML(@zip.read(file))]
+      end
+      @headers = Hash[filename_and_contents_pairs]
+    end
+
     def load_styles
       @styles_xml = @zip.read('word/styles.xml')
       @styles = Nokogiri::XML(@styles_xml)

spec/docx/document_spec.rb

@@ -60,6 +60,18 @@
     end
   end
 
+  describe 'read headers' do
+    before do
+      @doc = Docx::Document.open(@fixtures_path + '/multi_doc.docx')
+    end
+
+    it 'can extract headers' do
+      expect(@doc.headers).to_not be_nil
+      expect(@doc.headers.keys).to eq ["header1"]
+      expect(@doc.headers["header1"].text).to eq "Hello from the header."
+    end
+  end
+
   describe 'read tables' do
     before do
       @doc = Docx::Document.open(@fixtures_path + '/tables.docx')