Parse XLSX files with unusual structure

Normally you will find `workbook.xml` in the `xl` directory, but recently we got a file where it was located in the root.

To find the actual location of workbook, we must parse the file `_rels/.rels`. A separate rels file located relative to the workbook then points out the locations of the sheets, styles and shared strings.

Author: stenlarsson

lib/creek/book.rb

@@ -8,7 +8,9 @@ class Creek::Book
     attr_reader :files,
                 :sheets,
                 :shared_strings,
-                :with_headers
+                :with_headers,
+                :workbook_rels_by_type,
+                :workbook_rels_by_id
 
     DATE_1900 = Date.new(1899, 12, 30).freeze
     DATE_1904 = Date.new(1904, 1, 1).freeze
@@ -21,12 +23,14 @@ def initialize path, options = {}
       end
       path = download_file(path) if options[:remote]
       @files = Zip::File.open(path)
+      parse_workbook_path
+      parse_workbook_rels
       @shared_strings = SharedStrings.new(self)
       @with_headers = options.fetch(:with_headers, false)
     end
 
     def sheets
-      doc = @files.file.open "xl/workbook.xml"
+      doc = @files.file.open @workbook_path
       xml = Nokogiri::XML::Document.parse doc
       namespaces = xml.namespaces
 
@@ -37,10 +41,8 @@ def sheets
         end
       end
 
-      rels_doc = @files.file.open "xl/_rels/workbook.xml.rels"
-      rels = Nokogiri::XML::Document.parse(rels_doc).css("Relationship")
       @sheets = xml.css(cssPrefix+'sheet').map do |sheet|
-        sheetfile = rels.find { |el| sheet.attr("r:id") == el.attr("Id") }.attr("Target")
+        sheetfile = @workbook_rels_by_id[sheet.attr("r:id")]
         sheet = Sheet.new(
           self,
           sheet.attr("name"),
@@ -71,7 +73,7 @@ def base_date
         # http://msdn.microsoft.com/en-us/library/ff530155(v=office.12).aspx
         result = DATE_1900 # default
 
-        doc = @files.file.open "xl/workbook.xml"
+        doc = @files.file.open @workbook_path
         xml = Nokogiri::XML::Document.parse doc
         xml.css('workbookPr[date1904]').each do |workbookPr|
           if workbookPr['date1904'] =~ /true|1/i
@@ -98,5 +100,25 @@ def download_file(url)
         downloaded.path
       end
     end
+
+    def parse_workbook_path
+      rels_file = @files.file.open '_rels/.rels'
+      rels_xml = Nokogiri::XML::Document.parse(rels_file).css('Relationship')
+      rel = rels_xml.find { |el| el.attr('Type') == "http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" }
+      @workbook_path = rel.attr('Target')
+    end
+
+    def parse_workbook_rels
+      @workbook_rels_by_id = {}
+      @workbook_rels_by_type = {}
+      workbook_dirname, slash, workbook_basename = @workbook_path.rpartition('/')
+      workbook_rels_file = @files.file.open "#{workbook_dirname}#{slash}_rels/#{workbook_basename}.rels"
+      Nokogiri::XML::Document.parse(workbook_rels_file).css('Relationship').each do |rel|
+        target = rel.attr('Target')
+        target = "#{workbook_dirname}#{slash}#{target}" unless target.start_with?('/')
+        @workbook_rels_by_id[rel.attr('Id')] = target
+        @workbook_rels_by_type[rel.attr('Type')] = target
+      end
+    end
   end
 end

lib/creek/shared_strings.rb

@@ -13,8 +13,8 @@ def initialize book
     end
 
     def parse_shared_shared_strings
-      path = "xl/sharedStrings.xml"
-      if @book.files.file.exist?(path)
+      path = @book.workbook_rels_by_type["http://schemas.openxmlformats.org/officeDocument/2006/relationships/sharedStrings"]
+      if path
         doc = @book.files.file.open path
         xml = Nokogiri::XML::Document.parse doc
         parse_shared_string_from_document(xml)

lib/creek/styles.rb

@@ -6,12 +6,12 @@ def initialize(book)
     end
 
     def path
-      "xl/styles.xml"
+      @book.workbook_rels_by_type["http://schemas.openxmlformats.org/officeDocument/2006/relationships/styles"]
     end
 
     def styles_xml
       @styles_xml ||= begin
-        if @book.files.file.exist?(path)
+        if path
           doc = @book.files.file.open path
           Nokogiri::XML::Document.parse doc
         end

spec/fixtures/test_structure.xlsx

@@ -166,3 +166,21 @@
     expect(rows.map{|r| r['cells']}).to eq(@expected_rows)
   end
 end
+
+describe 'Creek parsing a file with unusual structure.' do
+  before(:all) do
+    @creek = Creek::Book.new 'spec/fixtures/test_structure.xlsx'
+    @expected_rows = [
+      {"A1"=>"date", "B1"=>"dimension", "C1"=>"metric_1", "D1"=>"metric_2", "E1"=>"metric_3"},
+      {"A2"=>"2022-02-27", "B2"=>"A", "C2"=>"1", "D2"=>"5.30", "E2"=>"11:11:11"}
+    ]
+  end
+
+  after(:all) do
+    @creek.close
+  end
+
+  it 'Parse rows successfully.' do
+    expect(@creek.sheets[0].rows.to_a).to eq(@expected_rows)
+  end
+end