Question

I am using nokogiri and ruby to script some deployment scripts and I need to update the file from many sources of information. The first file I loop through I just do a simple replace with gsub

File.open(@sql_file, 'w') { |file| file.puts text.gsub(/#{find}/, replace.to_s) }

That works great for the first file but for the second time I need to parse out that text I replaced initially and potentially update it. Using Nokogiri I have come up with the following:

def write_changes(find, replace)
  text = ''
  text = File.read(@sql_file)
  if text =~ /#{find}/
    File.open(@sql_file, 'w') do |file| 
      file.puts text.gsub(/#{find}/, replace.to_s)
    end
  else
    xml = Nokogiri::XML.parse(replace)
    element xml.at_xpath('//items')
  end
end

Maybe not very ruby:ish but it works. The problem here though is that I need to parse out

<items id="">
  <item />
</items>

from the text in the file so that I can use Nokogiri to update that text and later replace it with my changes.

So basically I guess I need to find the startindex of my items tag where the id matches and then cut out everything from <items id=""> to </items>.

Does it make sense? Should I clarify further?

EDIT 1. I have something somewhat working but I can’t figure out the last part.

    original = text[begin_index, end_index]
    xml2 = Nokogiri::XML.parse(original)
    update_element_values(xml, xml2)
    add_missing_elements(xml, xml2)
    # text[begin_index, end_index] = xml2.root.to_s
    text.insert(begin_index, xml2.root.to_s)
    File.open(@sql_file, 'w') { |file| file.puts text }

if I uncomment the line that does a replace between indexes I get some corrupt chopped up result with most of it missing.

If I use the insert version I get duplicates for every file I try to merge. What is the correct way to do replace between two indexes in a string in ruby?

Answer 1

My solution inspired by @Andrew’s comment was to use open the text as a html document to be able to navigate to the xpath and do replacement on that. After that is done i just clean up the generated html headers. Wish there was a better way though.

def replace_provider(xml)
  element = xml.at_xpath('//provider')
  return if element.nil?

  doc = Nokogiri::HTML(open(@sql_file))
  original_xml = doc.at_xpath("//provider[@name=\"#{element['name']}\"]")
  return if original_xml.nil?

  update_element_values(xml, original_xml)
  add_missing_elements(xml, original_xml)

  doc.xpath("//provider[@name=\"#{element['name']}\"]") do |item|
    item.replace original_xml
  end
  text = remove_all_html_tags(doc)
  File.open(@sql_file, 'w') { |file| file.puts text }
end