class Sass::CSS

def build_tree
  root = Sass::SCSS::CssParser.new(@template).parse
  expand_commas      root
  parent_ref_rules   root
  remove_parent_refs root
  flatten_rules      root
  fold_commas        root
  root
end

def check_encoding!
  return if @checked_encoding
  @checked_encoding = true
  @template, @original_encoding = Haml::Util.check_sass_encoding(@template) do |msg, line|
    raise Sass::SyntaxError.new(msg, :line => line)
  end
end

def expand_commas(root)
  root.children.map! do |child|
    unless child.is_a?(Tree::RuleNode) && child.rule.first.include?(',')
      expand_commas(child) if child.is_a?(Tree::DirectiveNode)
      next child
    end
    child.rule.first.split(',').map do |rule|
      node = Tree::RuleNode.new([rule.strip])
      node.children = child.children
      node
    end
  end
  root.children.flatten!
end

def flatten_rule(rule)
  while rule.children.size == 1 && rule.children.first.is_a?(Tree::RuleNode)
    child = rule.children.first
    if child.rule.first[0] == ?&
      rule.rule = [child.rule.first.gsub(/^&/, rule.rule.first)]
    else
      rule.rule = ["#{rule.rule.first} #{child.rule.first}"]
    end
    rule.children = child.children
  end
  flatten_rules(rule)
end

def flatten_rules(root)
  root.children.each do |child|
    case child
    when Tree::RuleNode
      flatten_rule(child)
    when Tree::DirectiveNode
      flatten_rules(child)
    end
  end
end

def fold_commas(root)
  prev_rule = nil
  root.children.map! do |child|
    unless child.is_a?(Tree::RuleNode)
      fold_commas(child) if child.is_a?(Tree::DirectiveNode)
      next child
    end
    if prev_rule && prev_rule.children == child.children
      prev_rule.rule.first << ", #{child.rule.first}"
      next nil
    end
    fold_commas(child)
    prev_rule = child
    child
  end
  root.children.compact!
end

def initialize(template, options = {})
  if template.is_a? IO
    template = template.read
  end
  @options = options.dup
  # Backwards compatibility
  @options[:old] = true if @options[:alternate] == false
  @template = template
end

def parent_ref_rules(root)
  current_rule = nil
  root.children.map! do |child|
    unless child.is_a?(Tree::RuleNode)
      parent_ref_rules(child) if child.is_a?(Tree::DirectiveNode)
      next child
    end
    first, rest = child.rule.first.scan(/\A(&?(?: .|[^ ])[^.#: \[]*)([.#: \[].*)?\Z/m).first
    if current_rule.nil? || current_rule.rule.first != first
      current_rule = Tree::RuleNode.new([first])
    end
    if rest
      child.rule = ["&" + rest]
      current_rule << child
    else
      current_rule.children += child.children
    end
    current_rule
  end
  root.children.compact!
  root.children.uniq!
  root.children.each { |v| parent_ref_rules(v) }
end

def remove_parent_refs(root)
  root.children.each do |child|
    case child
    when Tree::RuleNode
      child.rule.first.gsub! /^& +/, ''
      remove_parent_refs child
    when Tree::DirectiveNode
      remove_parent_refs child
    end
  end
end

def render(fmt = :sass)
  check_encoding!
  build_tree.send("to_#{fmt}", @options).strip + "\n"
rescue Sass::SyntaxError => err
  err.modify_backtrace(:filename => @options[:filename] || '(css)')
  raise err
end

def source_encoding
  check_encoding!
  @original_encoding
end