module Haml::Filters::Base

def self.included(base)
  Filters.defined[base.name.split("::").last.downcase] = base
  base.extend(base)
end

def compile(compiler, text)
  resolve_lazy_requires
  filter = self
  compiler.instance_eval do
    if contains_interpolation?(text)
      return if options[:suppress_eval]
      text = unescape_interpolation(text).gsub(/(\\+)n/) do |s|
        escapes = $1.size
        next s if escapes % 2 == 0
        ("\\" * (escapes - 1)) + "\n"
      end
      # We need to add a newline at the beginning to get the
      # filter lines to line up (since the Haml filter contains
      # a line that doesn't show up in the source, namely the
      # filter name). Then we need to escape the trailing
      # newline so that the whole filter block doesn't take up
      # too many.
      text = "\n" + text.sub(/\n"\Z/, "\\n\"")
      push_script <<RUBY.rstrip, :escape_html => false
nd_preserve(#{filter.inspect}.render_with_options(#{text}, _hamlout.options))
      return
    end
    rendered = Haml::Helpers::find_and_preserve(filter.render_with_options(text, compiler.options), compiler.options[:preserve])
    if !options[:ugly]
      push_text(rendered.rstrip.gsub("\n", "\n#{'  ' * @output_tabs}"))
    else
      push_text(rendered.rstrip)
    end
  end
end

def internal_compile(*args)
  resolve_lazy_requires
  compile(*args)
end

def lazy_require(*reqs)
  @lazy_requires = reqs
end

def render(text)
  raise Error.new("#{self.inspect}#render not defined!")
end

def render_with_options(text, options)
  render(text)
end

def resolve_lazy_requires
  return unless @lazy_requires
  @lazy_requires[0...-1].each do |req|
    begin
      @required = req
      require @required
      return
    rescue LoadError; end # RCov doesn't see this, but it is run
  end
  begin
    @required = @lazy_requires[-1]
    require @required
  rescue LoadError => e
    classname = self.name.match(/\w+$/)[0]
    if @lazy_requires.size == 1
      raise Error.new("Can't run #{classname} filter; required file '#{@lazy_requires.first}' not found")
    else
      raise Error.new("Can't run #{classname} filter; required #{@lazy_requires.map { |r| "'#{r}'" }.join(' or ')}, but none were found")
    end
  end
end