Rails: adding to last object if conditions met - ruby-on-rails

Question

I've got a method that scans an HTML string and sort of formats it for prawnpdf:
def format_for_prawn(pdf, string, colour)
body = Nokogiri::HTML::DocumentFragment.parse(string)
result = body.xpath('./*|./text()')
result.each do |breaker|
if breaker.name == "h3"
pdf.fill_color colour
pdf.text breaker.text.to_s, :size => 16
pdf.move_down 5
else
pdf.fill_color '#444444'
pdf.text breaker.text.to_s, :size => 10, :leading => 1
pdf.move_down 10
end
end
end
It works great for <h3>s. In the event that some mid-paragraph <b> (or similar) tags are found it starts a new paragraph because that's where Nokogiri broke the string--which is the correct behaviour.
How could I add the bolded string to the last pdf.text function instead of calling a new pdf.text which results in a new paragraph?
I thought about making an array out of it all but then it'll be out of order with the <h3>s.
Any help would be appreciated.

Answer 1

My first thought was to do a negative match :
body.xpath( './node()[not(self::b)]' )
Sadly, this would exclude <b> rather than ignoring it :
> body = Nokogiri::HTML::DocumentFragment.parse %(<h3><b>foo</b></h3><h3>bar</h3>fooz<b>baz</b>whatever); true
> body.xpath( './node()[not(self::b)]' ).to_a
[
[0] <h3>
<b>foo</b>
</h3>,
[1] <h3>bar</h3>,
[2] fooz,
[3] whatever
]
So, you'll have no choice but using a buffer, here : we can iterate through nodes first, to populate a buffer regarding if we should have a new line or not, then iterate this buffer to have your lines added to pdf :
buffer = []
body.xpath( './node()' ).each do |node|
if %w[text b].include? node.name
# add to previous line or create one
buffer << [] unless buffer.count
buffer.last << { node: node }
else
# set content and create a new line
buffer << [ { node: node, title: node.name == 'h3' } ]
buffer << []
end
end
# Now, each first level item in buffer is a line,
# containing elements we just have to concatenate text of
# to pass to `pdf#text`
buffer.each do |line|
text = line.map do |part|
node = part[ :node ]
inner = node.text.to_s
# restore <b> tag if you want bold style in pdf
node.name == 'b' ? "<b>#{inner}</b>" : inner
end.join
if line.first
if line.first[ :title ]
pdf.fill_color colour
pdf.text text, :size => 16
pdf.move_down 5
else
pdf.fill_color '#444444'
# inline_format ensure basic html formating is used, <b> in our case
# See http://prawn.majesticseacreature.com/docs/0.11.1/Prawn/Text.html#method-i-text
pdf.text text, size: 10, leading: 1, inline_format: true
pdf.move_down 10
end
end
end
Of course, all of this is considering you do not control original html. Else, you should place your text nodes inside <p> or something, and there would not be problems anymore.