class Haml::Exec::Sass

def watch_or_update
  require 'sass'
  require 'sass/plugin'
  ::Sass::Plugin.options.merge! @options[:for_engine]
  ::Sass::Plugin.options[:unix_newlines] = @options[:unix_newlines]
  if @args[1] && !@args[0].include?(':')
    flag = @options[:update] ? "--update" : "--watch"
    err =
      if !File.exist?(@args[1])
        "doesn't exist"
      elsif @args[1] =~ /\.css$/
        "is a CSS file"
      end
    raise <<MSG if err
{@args[1]} #{err}.
you mean: sass #{flag} #{@args[0]}:#{@args[1]}
  end
  dirs, files = @args.map {|name| name.split(':', 2)}.
    partition {|i, _| File.directory? i}
  files.map! {|from, to| [from, to || from.gsub(/\..*?$/, '.css')]}
  dirs.map! {|from, to| [from, to || from]}
  ::Sass::Plugin.options[:template_location] = dirs
  ::Sass::Plugin.on_updating_stylesheet do |_, css|
    if File.exists? css
      puts_action :overwrite, :yellow, css
    else
      puts_action :create, :green, css
    end
  end
  ::Sass::Plugin.on_creating_directory {|dirname| puts_action :directory, :green, dirname}
  ::Sass::Plugin.on_deleting_css {|filename| puts_action :delete, :yellow, filename}
  ::Sass::Plugin.on_compilation_error do |error, _, _|
    raise error unless error.is_a?(::Sass::SyntaxError)
    puts_action :error, :red, "#{error.sass_filename} (Line #{error.sass_line}: #{error.message})"
  end
  if @options[:update]
    ::Sass::Plugin.update_stylesheets(files)
    return
  end
  puts ">>> Sass is watching for changes. Press Ctrl-C to stop."
  ::Sass::Plugin.on_template_modified {|template| puts ">>> Change detected to: #{template}"}
  ::Sass::Plugin.on_template_created {|template| puts ">>> New template detected: #{template}"}
  ::Sass::Plugin.on_template_deleted {|template| puts ">>> Deleted template detected: #{template}"}
  ::Sass::Plugin.watch(files)
end