module Compass::SassExtensions::Functions::InlineImage

  def inline_image(path, mime_type = nil)
    path = path.value
    real_path = File.join(Compass.configuration.images_path, path)
    inline_image_string(data(real_path), compute_mime_type(path, mime_type))
  end

  def inline_font_files(*args)
    raise Sass::SyntaxError, "An even number of arguments must be passed to font_files()" unless args.size % 2 == 0
    files = []
    while args.size > 0
      path = args.shift.value
      real_path = File.join(Compass.configuration.fonts_path, path)
      url = "url('data:#{compute_mime_type(path)};base64,#{data(real_path)}')"
      files << "#{url} format('#{args.shift}')"
    end
    Sass::Script::String.new(files.join(", "))
  end

protected
  def inline_image_string(data, mime_type)
    data = [data].flatten.pack('m').gsub("\n","")
    url = "url('data:#{mime_type};base64,#{data}')"
    Sass::Script::String.new(url)
  end

private
  def compute_mime_type(path, mime_type = nil)
    return mime_type if mime_type
    case path
    when /\.png$/i
      'image/png'
    when /\.jpe?g$/i
      'image/jpeg'
    when /\.gif$/i
      'image/gif'
    when /\.svg$/i
      'image/svg+xml'
    when /\.otf$/i
      'font/opentype'
    when /\.ttf$/i
      'font/truetype'
    when /\.woff$/i
      'font/woff'
    when /\.off$/i
      'font/openfont'
    when /\.([a-zA-Z]+)$/
      "image/#{Regexp.last_match(1).downcase}"
    else
      raise Compass::Error, "A mime type could not be determined for #{path}, please specify one explicitly."
    end
  end

  def data(real_path)
    if File.readable?(real_path)
      File.open(real_path, "rb") {|io| io.read}
    else
      raise Compass::Error, "File not found or cannot be read: #{real_path}"
    end
  end
end