class Burly::Parsers::HtmlParser

def attr_nodes
  @attr_nodes ||= context_node.xpath(*ATTRIBUTES_XPATHS)
end

def context_node
  @context_node ||= doc.search(*Array(@context)).first || doc
end

def doc
  @doc ||= Nokogiri.HTML5(@document)
end

def initialize(document, context: nil)
  @context = context
  super
end

def parse
  attr_nodes.flat_map do |attr_node|
    if SRCSET_ATTRIBUTES_MAP.key?(attr_node.name)
      urls_from_candidate_strings(attr_node.value.split(/\s*,\s*/))
    else
      attr_node.value.strip
    end
  end
end

def urls_from_candidate_strings(candidate_strings)
  candidate_strings.flat_map { |candidate_string| candidate_string.strip.split(/\s|$/)[0] }
end