class Temple::HTML::AttributeMerger

def contains_static?(exp)
  case exp[0]
  when :multi
    exp[1..-1].any? {|e| contains_static?(e) }
  when :escape
    contains_static?(exp[2])
  when :static
    true
  else
    false
  end
end

def on_html_attr(name, value)
  if empty_exp?(value)
    value
  elsif contains_static?(value)
    [:html, :attr, name, value]
  else
    tmp = unique_name
    [:multi,
     [:capture, tmp, compile(value)],
     [:if, "!#{tmp}.empty?",
      [:html, :attr, name, [:dynamic, tmp]]]]
  end
end

def on_html_attrs(*attrs)
  names = []
  result = {}
  attrs.each do |attr|
    raise(InvalidExpression, 'Attribute is not a html attr') if attr[0] != :html || attr[1] != :attr
    name, value = attr[2].to_s, attr[3]
    if result[name]
      delimiter = options[:attr_delimiter][name]
      raise "Multiple #{name} attributes specified" unless delimiter
      if empty_exp?(value)
        result[name] = [:html, :attr, name,
                        [:multi,
                         result[name][3],
                         value]]
      elsif contains_static?(value)
        result[name] = [:html, :attr, name,
                        [:multi,
                         result[name][3],
                         [:static, delimiter],
                         value]]
      else
        tmp = unique_name
        result[name] = [:html, :attr, name,
                        [:multi,
                         result[name][3],
                         [:capture, tmp, value],
                         [:if, "!#{tmp}.empty?",
                          [:multi,
                           [:static, delimiter],
                           [:dynamic, tmp]]]]]
      end
    else
      result[name] = attr
      names << name
    end
  end
  result = options[:sort_attrs] ? result.sort : names.map {|k| [k, result[k]] }
  [:multi, *result.map {|name,attr| compile(attr) }]
end