module Haml::Precompiler

def self.build_attributes(is_html, attr_wrapper, attributes = {})

This is a class method so it can be accessed from Buffer. 
def self.build_attributes(is_html, attr_wrapper, attributes = {})
  quote_escape = attr_wrapper == '"' ? """ : "'"
  other_quote_char = attr_wrapper == '"' ? "'" : '"'
  if attributes['data'].is_a?(Hash)
    attributes = attributes.dup
    attributes =
      Haml::Util.map_keys(attributes.delete('data')) {|name| "data-#{name}"}.merge(attributes)
  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 = Haml::Helpers.preserve(Haml::Helpers.escape_once(value.to_s))
    # We want to decide whether or not to escape quotes
    value.gsub!('"', '"')
    this_attr_wrapper = attr_wrapper
    if value.include? attr_wrapper
      if value.include? other_quote_char
        value = value.gsub(attr_wrapper, quote_escape)
      else
        this_attr_wrapper = other_quote_char
      end
    end
    " #{attr}=#{this_attr_wrapper}#{value}#{this_attr_wrapper}"
  end
  result.compact.sort.join
end

def self.filter_and_join(value, separator) 

def self.filter_and_join(value, separator)
  value = [value] unless value.is_a?(Array)
  return value.flatten.collect {|item| item ? item.to_s : nil}.compact.join(separator)
end

def self.parse_class_and_id(list)

that can then be merged with another attributes hash.
and `#` syntax, and returns a hash with them as attributes,
Iterates through the classes and ids supplied through `.`

This is a class method so it can be accessed from {Haml::Helpers}. 
def self.parse_class_and_id(list)
  attributes = {}
  list.scan(/([#.])([-_a-zA-Z0-9]+)/) do |type, property|
    case type
    when '.'
      if attributes['class']
        attributes['class'] += " "
      else
        attributes['class'] = ""
      end
      attributes['class'] += property
    when '#'; attributes['id'] = property
    end
  end
  attributes
end

def balance(*args) 

def balance(*args)
  res = Haml::Shared.balance(*args)
  return res if res
  raise SyntaxError.new("Unbalanced brackets.")
end

def block_opened? 

def block_opened?
  !flat? && @next_line.tabs > @line.tabs
end

def close

Closes the most recent item in `@to_close_stack`. 
def close
  tag, *rest = @to_close_stack.pop
  send("close_#{tag}", *rest)
end

def close_comment(has_conditional)

Closes a comment. 
def close_comment(has_conditional)
  @output_tabs -= 1
  @template_tabs -= 1
  close_tag = has_conditional ? "<![endif]-->" : "-->"
  push_text(close_tag, -1)
end

def close_element(value)

the most recently opened tag.
Puts a line in `@precompiled` that will add the closing tag of 
def close_element(value)
  tag, nuke_outer_whitespace, nuke_inner_whitespace = value
  @output_tabs -= 1 unless nuke_inner_whitespace
  @template_tabs -= 1
  rstrip_buffer! if nuke_inner_whitespace
  push_merged_text("</#{tag}>" + (nuke_outer_whitespace ? "" : "\n"),
                   nuke_inner_whitespace ? 0 : -1, !nuke_inner_whitespace)
  @dont_indent_next_line = nuke_outer_whitespace
end

def close_filtered(filter)

Closes a filtered block. 
def close_filtered(filter)
  filter.internal_compile(self, @filter_buffer)
  @flat = false
  @flat_spaces = nil
  @filter_buffer = nil
  @template_tabs -= 1
end

def close_haml_comment 

def close_haml_comment
  @haml_comment = false
  @template_tabs -= 1
end

def close_loud(command, add_newline, push_end = true)

Closes a loud Ruby block. 
def close_loud(command, add_newline, push_end = true)
  push_silent('end', true) if push_end
  @precompiled << command
  @template_tabs -= 1
  concat_merged_text("\n") if add_newline
end

def close_nil(*args) 

def close_nil(*args)
  @template_tabs -= 1
end

def close_script(_1, _2, push_end = true)

Closes a Ruby block. 
def close_script(_1, _2, push_end = true)
  push_silent("end", true) if push_end
  @template_tabs -= 1
end

def closes_flat?(line) 

def closes_flat?(line)
  line && !line.text.empty? && line.full !~ /^#{@flat_spaces}/
end

def concat_merged_text(text)

Concatenate `text` to `@buffer` without tabulation. 
def concat_merged_text(text)
  @to_merge << [:text, text, 0]
end

def contains_interpolation?(str) 

def contains_interpolation?(str)
  str.include?('#{')
end

def flat? 

def flat?
  @flat
end

def flush_merged_text 

def flush_merged_text
  return if @to_merge.empty?
  str = ""
  mtabs = 0
  newlines = 0
  @to_merge.each do |type, val, tabs|
    case type
    when :text
      str << val.inspect[1...-1]
      mtabs += tabs
    when :script
      if mtabs != 0 && !@options[:ugly]
        val = "_hamlout.adjust_tabs(#{mtabs}); " + val
      end
      str << "\#{#{"\n" * newlines}#{val}}"
      mtabs = 0
      newlines = 0
    when :newlines
      newlines += val
    else
      raise SyntaxError.new("[HAML BUG] Undefined entry in Haml::Precompiler@to_merge.")
    end
  end
  @precompiled <<
    if @options[:ugly]
      "_hamlout.buffer << \"#{str}\";"
    else
      "_hamlout.push_text(\"#{str}\", #{mtabs}, #{@dont_tab_up_next_text.inspect});"
    end
  @precompiled << "\n" * newlines
  @to_merge = []
  @dont_tab_up_next_text = false
end

def handle_multiline(line) 

def handle_multiline(line)
  return unless is_multiline?(line.text)
  line.text.slice!(-1)
  while new_line = raw_next_line.first
    break if new_line == :eod
    newline and next if new_line.strip.empty?
    break unless is_multiline?(new_line.strip)
    line.text << new_line.strip[0...-1]
    newline
  end
  un_next_line new_line
  resolve_newlines
end

def handle_ruby_multiline(text) 

def handle_ruby_multiline(text)
  text = text.rstrip
  return text unless is_ruby_multiline?(text)
  un_next_line @next_line.full
  begin
    new_line = raw_next_line.first
    break if new_line == :eod
    newline and next if new_line.strip.empty?
    text << " " << new_line.strip
    newline
  end while is_ruby_multiline?(new_line.strip)
  next_line
  resolve_newlines
  text
end

def is_multiline?(text)

Checks whether or not +line+ is in a multiline sequence. 
def is_multiline?(text)
  text && text.length > 1 && text[-1] == MULTILINE_CHAR_VALUE && text[-2] == ?\s
end

def is_ruby_multiline?(text) 

def is_ruby_multiline?(text)
  text && text.length > 1 && text[-1] == ?, && text[-2] != ?? && text[-3..-2] != "?\\"
end

def locals_code(names) 

def locals_code(names)
  names = names.keys if Hash == names
  names.map do |name|
    # Can't use || because someone might explicitly pass in false with a symbol
    sym_local = "_haml_locals[#{name.to_sym.inspect}]"
    str_local = "_haml_locals[#{name.to_s.inspect}]"
    "#{name} = #{sym_local}.nil? ? #{str_local} : #{sym_local}"
  end.join(';') + ';'
end

def mid_block_keyword?(text)

Otherwise, returns nil.
returns the name of that keyword.
If the text is a silent script text with one of Ruby's mid-block keywords, 
def mid_block_keyword?(text)
  text[MID_BLOCK_KEYWORD_REGEX, 1]
end

def newline 

def newline
  @newlines += 1
end

def newline_now 

def newline_now
  @precompiled << "\n"
  @newlines -= 1
end

def next_line 

def next_line
  text, index = raw_next_line
  return unless text
  # :eod is a special end-of-document marker
  line =
    if text == :eod
      Line.new '-#', '-#', '-#', index, self, true
    else
      Line.new text.strip, text.lstrip.chomp, text, index, self, false
    end
  # `flat?' here is a little outdated,
  # so we have to manually check if either the previous or current line
  # closes the flat block,
  # as well as whether a new block is opened
  @line.tabs if @line
  unless (flat? && !closes_flat?(line) && !closes_flat?(@line)) ||
      (@line && @line.text[0] == ?: && line.full =~ %r[^#{@line.full[/^\s+/]}\s])
    if line.text.empty?
      newline
      return next_line
    end
    handle_multiline(line)
  end
  @next_line = line
end

def parse_new_attribute(scanner) 

def parse_new_attribute(scanner)
  unless name = scanner.scan(/[-:\w]+/)
    return if scanner.scan(/\)/)
    return false
  end
  scanner.scan(/\s*/)
  return name, [:static, true] unless scanner.scan(/=/) #/end
  scanner.scan(/\s*/)
  unless quote = scanner.scan(/["']/)
    return false unless var = scanner.scan(/(@@?|\$)?\w+/)
    return name, [:dynamic, var]
  end
  re = /((?:\\.|\#(?!\{)|[^#{quote}\\#])*)(#{quote}|#\{)/
  content = []
  loop do
    return false unless scanner.scan(re)
    content << [:str, scanner[1].gsub(/\\(.)/, '\1')]
    break if scanner[2] == quote
    content << [:ruby, balance(scanner, ?{, ?}, 1).first[0...-1]]
  end
  return name, [:static, content.first[1]] if content.size == 1
  return name, [:dynamic,
    '"' + content.map {|(t, v)| t == :str ? v.inspect[1...-1] : "\#{#{v}}"}.join + '"']
end

def parse_new_attributes(line) 

def parse_new_attributes(line)
  line = line.dup
  scanner = StringScanner.new(line)
  last_line = @index
  attributes = {}
  scanner.scan(/\(\s*/)
  loop do
    name, value = parse_new_attribute(scanner)
    break if name.nil?
    if name == false
      text = (Haml::Shared.balance(line, ?(, ?)) || [line]).first
      raise Haml::SyntaxError.new("Invalid attribute list: #{text.inspect}.", last_line - 1)
    end
    attributes[name] = value
    scanner.scan(/\s*/)
    if scanner.eos?
      line << " " << @next_line.text
      last_line += 1
      next_line
      scanner.scan(/\s*/)
    end
  end
  static_attributes = {}
  dynamic_attributes = "{"
  attributes.each do |name, (type, val)|
    if type == :static
      static_attributes[name] = val
    else
      dynamic_attributes << name.inspect << " => " << val << ","
    end
  end
  dynamic_attributes << "}"
  dynamic_attributes = nil if dynamic_attributes == "{}"
  return [static_attributes, dynamic_attributes], scanner.rest, last_line
end

def parse_old_attributes(line) 

def parse_old_attributes(line)
  line = line.dup
  last_line = @index
  begin
    attributes_hash, rest = balance(line, ?{, ?})
  rescue SyntaxError => e
    if line.strip[-1] == ?, && e.message == "Unbalanced brackets."
      line << "\n" << @next_line.text
      last_line += 1
      next_line
      retry
    end
    raise e
  end
  attributes_hash = attributes_hash[1...-1] if attributes_hash
  return attributes_hash, rest, last_line
end

def parse_static_hash(text) 

def parse_static_hash(text)
  attributes = {}
  scanner = StringScanner.new(text)
  scanner.scan(/\s+/)
  until scanner.eos?
    return unless key = scanner.scan(LITERAL_VALUE_REGEX)
    return unless scanner.scan(/\s*=>\s*/)
    return unless value = scanner.scan(LITERAL_VALUE_REGEX)
    return unless scanner.scan(/\s*(?:,|$)\s*/)
    attributes[eval(key).to_s] = eval(value).to_s
  end
  text.count("\n").times { newline }
  attributes
end

def parse_tag(line)

Parses a line into tag_name, attributes, attributes_hash, object_ref, action, value 
def parse_tag(line)
  raise SyntaxError.new("Invalid tag: \"#{line}\".") unless match = line.scan(/%([-:\w]+)([-\w\.\#]*)(.*)/)[0]
  tag_name, attributes, rest = match
  new_attributes_hash = old_attributes_hash = last_line = object_ref = nil
  attributes_hashes = []
  while rest
    case rest[0]
    when ?{
      break if old_attributes_hash
      old_attributes_hash, rest, last_line = parse_old_attributes(rest)
      attributes_hashes << [:old, old_attributes_hash]
    when ?(
      break if new_attributes_hash
      new_attributes_hash, rest, last_line = parse_new_attributes(rest)
      attributes_hashes << [:new, new_attributes_hash]
    when ?[
      break if object_ref
      object_ref, rest = balance(rest, ?[, ?])
    else; break
    end
  end
  if rest
    nuke_whitespace, action, value = rest.scan(/(<>|><|[><])?([=\/\~&!])?(.*)?/)[0]
    nuke_whitespace ||= ''
    nuke_outer_whitespace = nuke_whitespace.include? '>'
    nuke_inner_whitespace = nuke_whitespace.include? '<'
  end
  value = value.to_s.strip
  [tag_name, attributes, attributes_hashes, object_ref, nuke_outer_whitespace,
   nuke_inner_whitespace, action, value, last_line || @index]
end

def precompile 

def precompile
  @haml_comment = @dont_indent_next_line = @dont_tab_up_next_text = false
  @indentation = nil
  @line = next_line
  resolve_newlines
  newline
  raise SyntaxError.new("Indenting at the beginning of the document is illegal.", @line.index) if @line.tabs != 0
  while next_line
    process_indent(@line) unless @line.text.empty?
    if flat?
      push_flat(@line)
      @line = @next_line
      next
    end
    process_line(@line.text, @line.index) unless @line.text.empty? || @haml_comment
    if !flat? && @next_line.tabs - @line.tabs > 1
      raise SyntaxError.new("The line was indented #{@next_line.tabs - @line.tabs} levels deeper than the previous line.", @next_line.index)
    end
    resolve_newlines unless @next_line.eod?
    @line = @next_line
    newline unless @next_line.eod?
  end
  # Close all the open tags
  close until @to_close_stack.empty?
  flush_merged_text
end

def precompiled_method_return_value

This method exists so it can be monkeypatched to return modified values.
Returns the string used as the return value of the precompiled method. 
def precompiled_method_return_value
  "_erbout"
end

def precompiled_with_ambles(local_names)

Returns the precompiled string with the preamble and postamble 
def precompiled_with_ambles(local_names)
  preamble = <<END.gsub("\n", ";")
n
nd Haml::Helpers
lout = @haml_buffer = Haml::Buffer.new(@haml_buffer, #{options_for_buffer.inspect})
out = _hamlout.buffer
_erb_template = true
  postamble = <<END.gsub("\n", ";")
ecompiled_method_return_value}
re
l_buffer = @haml_buffer.upper
  preamble + locals_code(local_names) + precompiled + postamble
end

def prerender_tag(name, self_close, attributes) 

def prerender_tag(name, self_close, attributes)
  attributes_string = Precompiler.build_attributes(html?, @options[:attr_wrapper], attributes)
  "<#{name}#{attributes_string}#{self_close && xhtml? ? ' /' : ''}>"
end

def process_indent(line)

Processes and deals with lowering indentation. 
def process_indent(line)
  return unless line.tabs <= @template_tabs && @template_tabs > 0
  to_close = @template_tabs - line.tabs
  to_close.times {|i| close unless to_close - 1 - i == 0 && mid_block_keyword?(line.text)}
end

def process_line(text, index)

adds the appropriate code to `@precompiled`.
This method doesn't return anything; it simply processes the line and

Processes a single line of Haml. 
def process_line(text, index)
  @index = index + 1
  case text[0]
  when DIV_CLASS; render_div(text)
  when DIV_ID
    return push_plain(text) if text[1] == ?{
    render_div(text)
  when ELEMENT; render_tag(text)
  when COMMENT; render_comment(text[1..-1].strip)
  when SANITIZE
    return push_plain(text[3..-1].strip, :escape_html => true) if text[1..2] == "=="
    return push_script(text[2..-1].strip, :escape_html => true) if text[1] == SCRIPT
    return push_flat_script(text[2..-1].strip, :escape_html => true) if text[1] == FLAT_SCRIPT
    return push_plain(text[1..-1].strip, :escape_html => true) if text[1] == ?\s
    push_plain text
  when SCRIPT
    return push_plain(text[2..-1].strip) if text[1] == SCRIPT
    push_script(text[1..-1])
  when FLAT_SCRIPT; push_flat_script(text[1..-1])
  when SILENT_SCRIPT
    return start_haml_comment if text[1] == SILENT_COMMENT
    raise SyntaxError.new(<<END.rstrip, index) if text[1..-1].strip == "end"
don't need to use "- end" in Haml. Un-indent to close a block:
 foo?
trong Foo!
se
t foo.
his line is un-indented, so it isn't part of the "if" block
    text = handle_ruby_multiline(text)
    push_silent(text[1..-1], true)
    newline_now
    # Handle stuff like - end.join("|")
    @to_close_stack.last << false if text =~ /^-\s*end\b/ && !block_opened?
    case_stmt = text =~ /^-\s*case\b/
    keyword = mid_block_keyword?(text)
    block = block_opened? && !keyword
    # It's important to preserve tabulation modification for keywords
    # that involve choosing between posible blocks of code.
    if %w[else elsif when].include?(keyword)
      # @to_close_stack may not have a :script on top
      # when the preceding "- if" has nothing nested
      if @to_close_stack.last && @to_close_stack.last.first == :script
        @dont_indent_next_line, @dont_tab_up_next_text = @to_close_stack.last[1..2]
      else
        push_and_tabulate([:script, @dont_indent_next_line, @dont_tab_up_next_text])
      end
      # when is unusual in that either it will be indented twice,
      # or the case won't have created its own indentation
      if keyword == "when"
        push_and_tabulate([:script, @dont_indent_next_line, @dont_tab_up_next_text, false])
      end
    elsif block || case_stmt
      push_and_tabulate([:script, @dont_indent_next_line, @dont_tab_up_next_text])
    elsif block && case_stmt
      push_and_tabulate([:script, @dont_indent_next_line, @dont_tab_up_next_text])
    end
  when FILTER; start_filtered(text[1..-1].downcase)
  when DOCTYPE
    return render_doctype(text) if text[0...3] == '!!!'
    return push_plain(text[3..-1].strip, :escape_html => false) if text[1..2] == "=="
    return push_script(text[2..-1].strip, :escape_html => false) if text[1] == SCRIPT
    return push_flat_script(text[2..-1].strip, :escape_html => false) if text[1] == FLAT_SCRIPT
    return push_plain(text[1..-1].strip, :escape_html => false) if text[1] == ?\s
    push_plain text
  when ESCAPE; push_plain text[1..-1]
  else push_plain text
  end
end

def push_and_tabulate(value)

`@template_tabs`.
Pushes value onto `@to_close_stack` and increases 
def push_and_tabulate(value)
  @to_close_stack.push(value)
  @template_tabs += 1
end

def push_flat(line)

Adds +text+ to `@buffer` while flattening text. 
def push_flat(line)
  text = line.full.dup
  text = "" unless text.gsub!(/^#{@flat_spaces}/, '')
  @filter_buffer << "#{text}\n"
end

def push_flat_script(text, options = {})

to be run on it afterwards.
Causes `text` to be evaluated, and Haml::Helpers#find_and_flatten 
def push_flat_script(text, options = {})
  flush_merged_text
  raise SyntaxError.new("There's no Ruby code for ~ to evaluate.") if text.empty?
  push_script(text, options.merge(:preserve_script => true))
end

def push_merged_text(text, tab_change = 0, indent = true)

without parsing it.
Adds `text` to `@buffer` with appropriate tabulation 
def push_merged_text(text, tab_change = 0, indent = true)
  text = !indent || @dont_indent_next_line || @options[:ugly] ? text : "#{'  ' * @output_tabs}#{text}"
  @to_merge << [:text, text, tab_change]
  @dont_indent_next_line = false
end

def push_plain(text, options = {})

Also checks for an illegally opened block.
Renders a block of text as plain text. 
def push_plain(text, options = {})
  if block_opened?
    raise SyntaxError.new("Illegal nesting: nesting within plain text is illegal.", @next_line.index)
  end
  if contains_interpolation?(text)
    options[:escape_html] = self.options[:escape_html] if options[:escape_html].nil?
    push_script(
      unescape_interpolation(text, :escape_html => options[:escape_html]),
      :escape_html => false)
  else
    push_text text
  end
end

def push_script(text, opts = {})

the result before it is added to `@buffer`
If `opts[:preserve_script]` is true, Haml::Helpers#find_and_flatten is run on

the scope object and the result to be added to `@buffer`.
Causes `text` to be evaluated in the context of 
def push_script(text, opts = {})
  raise SyntaxError.new("There's no Ruby code for = to evaluate.") if text.empty?
  text = handle_ruby_multiline(text)
  return if options[:suppress_eval]
  opts[:escape_html] = options[:escape_html] if opts[:escape_html].nil?
  args = %w[preserve_script in_tag preserve_tag escape_html nuke_inner_whitespace]
  args.map! {|name| opts[name.to_sym]}
  args << !block_opened? << @options[:ugly]
  no_format = @options[:ugly] &&
    !(opts[:preserve_script] || opts[:preserve_tag] || opts[:escape_html])
  output_expr = "(#{text}\n)"
  static_method = "_hamlout.#{static_method_name(:format_script, *args)}"
  # Prerender tabulation unless we're in a tag
  push_merged_text '' unless opts[:in_tag]
  unless block_opened?
    @to_merge << [:script, no_format ? "#{text}\n" : "#{static_method}(#{output_expr});"]
    concat_merged_text("\n") unless opts[:in_tag] || opts[:nuke_inner_whitespace]
    @newlines -= 1
    return
  end
  flush_merged_text
  push_silent "haml_temp = #{text}"
  newline_now
  push_and_tabulate([:loud, "_hamlout.buffer << #{no_format ? "haml_temp.to_s;" : "#{static_method}(haml_temp);"}",
    !(opts[:in_tag] || opts[:nuke_inner_whitespace] || @options[:ugly])])
end

def push_silent(text, can_suppress = false)

does not output the result.
Evaluates `text` in the context of the scope object, but 
def push_silent(text, can_suppress = false)
  flush_merged_text
  return if can_suppress && options[:suppress_eval]
  @precompiled << "#{text};"
end

def push_silent_with_haml_block_deprecation(text, can_suppress = false) 

def push_silent_with_haml_block_deprecation(text, can_suppress = false)
  unless can_suppress && block_opened? && !mid_block_keyword?("- #{text}") &&
      text =~ ActionView::Template::Handlers::Erubis::BLOCK_EXPR
    return push_silent_without_haml_block_deprecation(text, can_suppress)
  end
  push_silent_without_haml_block_deprecation("_hamlout.append_if_string= #{text}", can_suppress)
end

def push_text(text, tab_change = 0) 

def push_text(text, tab_change = 0)
  push_merged_text("#{text}\n", tab_change)
end

def raw_next_line 

def raw_next_line
  text = @template.shift
  return unless text
  index = @template_index
  @template_index += 1
  return text, index
end

def render_comment(line)

Renders an XHTML comment. 
def render_comment(line)
  conditional, line = balance(line, ?[, ?]) if line[0] == ?[
  line.strip!
  conditional << ">" if conditional
  if block_opened? && !line.empty?
    raise SyntaxError.new('Illegal nesting: nesting within a tag that already has content is illegal.', @next_line.index)
  end
  open = "<!--#{conditional}"
  # Render it statically if possible
  unless line.empty?
    return push_text("#{open} #{line} #{conditional ? "<![endif]-->" : "-->"}")
  end
  push_text(open, 1)
  @output_tabs += 1
  push_and_tabulate([:comment, !conditional.nil?])
  unless line.empty?
    push_text(line)
    close
  end
end

def render_div(line)

`.` or `#`.
Renders a line that creates an XHTML tag and has an implicit div because of 
def render_div(line)
  render_tag('%div' + line)
end

def render_doctype(line)

Renders an XHTML doctype or XML shebang. 
def render_doctype(line)
  raise SyntaxError.new("Illegal nesting: nesting within a header command is illegal.", @next_line.index) if block_opened?
  doctype = text_for_doctype(line)
  push_text doctype if doctype
end

def render_tag(line)

render that tag to `@precompiled`.
Parses a line that will render as an XHTML tag, and adds the code that will 
def render_tag(line)
  tag_name, attributes, attributes_hashes, object_ref, nuke_outer_whitespace,
    nuke_inner_whitespace, action, value, last_line = parse_tag(line)
  raise SyntaxError.new("Illegal element: classes and ids must have values.") if attributes =~ /[\.#](\.|#|\z)/
  # Get rid of whitespace outside of the tag if we need to
  rstrip_buffer! if nuke_outer_whitespace
  preserve_tag = options[:preserve].include?(tag_name)
  nuke_inner_whitespace ||= preserve_tag
  preserve_tag &&= !options[:ugly]
  escape_html = (action == '&' || (action != '!' && @options[:escape_html]))
  case action
  when '/'; self_closing = true
  when '~'; parse = preserve_script = true
  when '='
    parse = true
    if value[0] == ?=
      value = unescape_interpolation(value[1..-1].strip, :escape_html => escape_html)
      escape_html = false
    end
  when '&', '!'
    if value[0] == ?= || value[0] == ?~
      parse = true
      preserve_script = (value[0] == ?~)
      if value[1] == ?=
        value = unescape_interpolation(value[2..-1].strip, :escape_html => escape_html)
        escape_html = false
      else
        value = value[1..-1].strip
      end
    elsif contains_interpolation?(value)
      value = unescape_interpolation(value, :escape_html => escape_html)
      parse = true
      escape_html = false
    end
  else
    if contains_interpolation?(value)
      value = unescape_interpolation(value, :escape_html => escape_html)
      parse = true
      escape_html = false
    end
  end
  if parse && @options[:suppress_eval]
    parse = false
    value = ''
  end
  object_ref = "nil" if object_ref.nil? || @options[:suppress_eval]
  attributes = Precompiler.parse_class_and_id(attributes)
  attributes_hashes.map! do |syntax, attributes_hash|
    if syntax == :old
      static_attributes = parse_static_hash(attributes_hash)
      attributes_hash = nil if static_attributes || @options[:suppress_eval]
    else
      static_attributes, attributes_hash = attributes_hash
    end
    Buffer.merge_attrs(attributes, static_attributes) if static_attributes
    attributes_hash
  end.compact!
  raise SyntaxError.new("Illegal nesting: nesting within a self-closing tag is illegal.", @next_line.index) if block_opened? && self_closing
  raise SyntaxError.new("There's no Ruby code for #{action} to evaluate.", last_line - 1) if parse && value.empty?
  raise SyntaxError.new("Self-closing tags can't have content.", last_line - 1) if self_closing && !value.empty?
  if block_opened? && !value.empty? && !is_ruby_multiline?(value)
    raise SyntaxError.new("Illegal nesting: content can't be both given on the same line as %#{tag_name} and nested within it.", @next_line.index)
  end
  self_closing ||= !!(!block_opened? && value.empty? && @options[:autoclose].any? {|t| t === tag_name})
  value = nil if value.empty? && (block_opened? || self_closing)
  dont_indent_next_line =
    (nuke_outer_whitespace && !block_opened?) ||
    (nuke_inner_whitespace && block_opened?)
  # Check if we can render the tag directly to text and not process it in the buffer
  if object_ref == "nil" && attributes_hashes.empty? && !preserve_script
    tag_closed = !block_opened? && !self_closing && !parse
    open_tag  = prerender_tag(tag_name, self_closing, attributes)
    if tag_closed
      open_tag << "#{value}</#{tag_name}>"
      open_tag << "\n" unless nuke_outer_whitespace
    else
      open_tag << "\n" unless parse || nuke_inner_whitespace || (self_closing && nuke_outer_whitespace)
    end
    push_merged_text(open_tag, tag_closed || self_closing || nuke_inner_whitespace ? 0 : 1,
                     !nuke_outer_whitespace)
    @dont_indent_next_line = dont_indent_next_line
    return if tag_closed
  else
    flush_merged_text
    content = parse ? 'nil' : value.inspect
    if attributes_hashes.empty?
      attributes_hashes = ''
    elsif attributes_hashes.size == 1
      attributes_hashes = ", #{attributes_hashes.first}"
    else
      attributes_hashes = ", (#{attributes_hashes.join(").merge(")})"
    end
    args = [tag_name, self_closing, !block_opened?, preserve_tag, escape_html,
            attributes, nuke_outer_whitespace, nuke_inner_whitespace
           ].map { |v| v.inspect }.join(', ')
    push_silent "_hamlout.open_tag(#{args}, #{object_ref}, #{content}#{attributes_hashes})"
    @dont_tab_up_next_text = @dont_indent_next_line = dont_indent_next_line
  end
  return if self_closing
  if value.nil?
    push_and_tabulate([:element, [tag_name, nuke_outer_whitespace, nuke_inner_whitespace]])
    @output_tabs += 1 unless nuke_inner_whitespace
    return
  end
  if parse
    push_script(value, :preserve_script => preserve_script, :in_tag => true,
      :preserve_tag => preserve_tag, :escape_html => escape_html,
      :nuke_inner_whitespace => nuke_inner_whitespace)
    concat_merged_text("</#{tag_name}>" + (nuke_outer_whitespace ? "" : "\n"))
  end
end

def resolve_newlines 

def resolve_newlines
  return unless @newlines > 0
  @to_merge << [:newlines, @newlines]
  @newlines = 0
end

def rstrip_buffer!(index = -1)

or the merged text
Get rid of and whitespace at the end of the buffer 
def rstrip_buffer!(index = -1)
  last = @to_merge[index]
  if last.nil?
    push_silent("_hamlout.rstrip!", false)
    @dont_tab_up_next_text = true
    return
  end
  case last.first
  when :text
    last[1].rstrip!
    if last[1].empty?
      @to_merge.slice! index
      rstrip_buffer! index
    end
  when :script
    last[1].gsub!(/\(haml_temp, (.*?)\);$/, '(haml_temp.rstrip, \1);')
    rstrip_buffer! index - 1
  when :newlines
    rstrip_buffer! index - 1
  else
    raise SyntaxError.new("[HAML BUG] Undefined entry in Haml::Precompiler@to_merge.")
  end
end

def start_filtered(name)

Starts a filtered block. 
def start_filtered(name)
  raise Error.new("Invalid filter name \":#{name}\".") unless name =~ /^\w+$/
  raise Error.new("Filter \"#{name}\" is not defined.") unless filter = Filters.defined[name]
  push_and_tabulate([:filtered, filter])
  @flat = true
  @filter_buffer = String.new
  # If we don't know the indentation by now, it'll be set in Line#tabs
  @flat_spaces = @indentation * @template_tabs if @indentation
end

def start_haml_comment 

def start_haml_comment
  return unless block_opened?
  @haml_comment = true
  push_and_tabulate([:haml_comment])
end

def text_for_doctype(text) 

def text_for_doctype(text)
  text = text[3..-1].lstrip.downcase
  if text.index("xml") == 0
    return nil if html?
    wrapper = @options[:attr_wrapper]
    return "<?xml version=#{wrapper}1.0#{wrapper} encoding=#{wrapper}#{text.split(' ')[1] || "utf-8"}#{wrapper} ?>"
  end
  if html5?
    '<!DOCTYPE html>'
  else
    version, type = text.scan(DOCTYPE_REGEX)[0]
    if xhtml?
      if version == "1.1"
        '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">'
      elsif version == "5"
        '<!DOCTYPE html>'
      else
        case type
        when "strict";   '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">'
        when "frameset"; '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">'
        when "mobile";   '<!DOCTYPE html PUBLIC "-//WAPFORUM//DTD XHTML Mobile 1.2//EN" "http://www.openmobilealliance.org/tech/DTD/xhtml-mobile12.dtd">'
        when "rdfa";     '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN" "http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd">'
        when "basic";    '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.1//EN" "http://www.w3.org/TR/xhtml-basic/xhtml-basic11.dtd">'
        else             '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">'
        end
      end
    elsif html4?
      case type
      when "strict";   '<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">'
      when "frameset"; '<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">'
      else             '<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">'
      end
    end
  end
end

def un_next_line(line) 

def un_next_line(line)
  @template.unshift line
  @template_index -= 1
end

def unescape_interpolation(str, opts = {}) 

def unescape_interpolation(str, opts = {})
  res = ''
  rest = Haml::Shared.handle_interpolation str.dump do |scan|
    escapes = (scan[2].size - 1) / 2
    res << scan.matched[0...-3 - escapes]
    if escapes % 2 == 1
      res << '#{'
    else
      content = eval('"' + balance(scan, ?{, ?}, 1)[0][0...-1] + '"')
      content = "Haml::Helpers.html_escape(#{content})" if opts[:escape_html]
      res << '#{' + content + "}"# Use eval to get rid of string escapes
    end
  end
  res + rest
end