class Temple::HTML::AttributeMerger

def on_html_attrs(*attrs)
  names = []
  values = {}
  attrs.each do |attr|
    name, value = attr[2].to_s, attr[3]
    if values[name]
      raise(FilterError, "Multiple #{name} attributes specified") unless options[:merge_attrs][name]
      values[name] << value
    else
      values[name] = [value]
      names << name
    end
  end
  attrs = names.map do |name|
    value = values[name]
    if (delimiter = options[:merge_attrs][name]) && value.size > 1
      exp = [:multi]
      if value.all? {|v| contains_nonempty_static?(v) }
        exp << value.first
        value[1..-1].each {|v| exp << [:static, delimiter] << v }
        [:html, :attr, name, exp]
      else
        captures = unique_name
        exp << [:code, "#{captures} = []"]
        value.each_with_index {|v, i| exp << [:capture, "#{captures}[#{i}]", v] }
        exp << [:dynamic, "#{captures}.reject(&:empty?).join(#{delimiter.inspect})"]
      end
      [:html, :attr, name, exp]
    else
      [:html, :attr, name, value.first]
    end
  end
  [:html, :attrs, *attrs]
end