module Haml::AttributeBuilder

def build_attributes(is_html, attr_wrapper, escape_attrs, hyphenate_data_attrs, attributes = {})
  # @TODO this is an absolutely ridiculous amount of arguments. At least
  # some of this needs to be moved into an instance method.
  join_char = hyphenate_data_attrs ? '-' : '_'
  attributes.each do |key, value|
    if value.is_a?(Hash)
      data_attributes = attributes.delete(key)
      data_attributes = flatten_data_attributes(data_attributes, '', join_char)
      data_attributes = build_data_keys(data_attributes, hyphenate_data_attrs, key)
      verify_attribute_names!(data_attributes.keys)
      attributes = data_attributes.merge(attributes)
    end
  end
  result = attributes.collect do |attr, value|
    next if value.nil?
    value = filter_and_join(value, ' ') if attr == 'class'
    value = filter_and_join(value, '_') if attr == 'id'
    if value == true
      next " #{attr}" if is_html
      next " #{attr}=#{attr_wrapper}#{attr}#{attr_wrapper}"
    elsif value == false
      next
    end
    value =
      if escape_attrs == :once
        Haml::Helpers.escape_once(value.to_s)
      elsif escape_attrs
        Haml::Helpers.html_escape(value.to_s)
      else
        value.to_s
      end
    " #{attr}=#{attr_wrapper}#{value}#{attr_wrapper}"
  end
  result.compact!
  result.sort!
  result.join
end

def build_data_keys(data_hash, hyphenate, attr_name="data")
  Hash[data_hash.map do |name, value|
    if name == nil
      [attr_name, value]
    elsif hyphenate
      ["#{attr_name}-#{name.to_s.tr('_', '-')}", value]
    else
      ["#{attr_name}-#{name}", value]
    end
  end]
end

def filter_and_join(value, separator)
  return '' if (value.respond_to?(:empty?) && value.empty?)
  if value.is_a?(Array)
    value = value.flatten
    value.map! {|item| item ? item.to_s : nil}
    value.compact!
    value = value.join(separator)
  else
    value = value ? value.to_s : nil
  end
  !value.nil? && !value.empty? && value
end

def flatten_data_attributes(data, key, join_char, seen = [])
  return {key => data} unless data.is_a?(Hash)
  return {key => nil} if seen.include? data.object_id
  seen << data.object_id
  data.sort {|x, y| x[0].to_s <=> y[0].to_s}.inject({}) do |hash, (k, v)|
    joined = key == '' ? k : [key, k].join(join_char)
    hash.merge! flatten_data_attributes(v, joined, join_char, seen)
  end
end

def merge_attributes!(to, from)
  from.keys.each do |key|
    to[key] = merge_value(key, to[key], from[key])
  end
  to
end

def merge_value(key, to, from)
  if from.kind_of?(Hash) || to.kind_of?(Hash)
    from = { nil => from } if !from.is_a?(Hash)
    to   = { nil => to }   if !to.is_a?(Hash)
    to.merge(from)
  elsif key == 'id'
    merged_id = filter_and_join(from, '_')
    if to && merged_id
      merged_id = "#{to}_#{merged_id}"
    elsif to || merged_id
      merged_id ||= to
    end
    merged_id
  elsif key == 'class'
    merged_class = filter_and_join(from, ' ')
    if to && merged_class
      merged_class = (merged_class.split(' ') | to.split(' ')).sort.join(' ')
    elsif to || merged_class
      merged_class ||= to
    end
    merged_class
  else
    from
  end
end