module Mongrel # :nodoc: all
  class DirHandler

    # This isn't proper class-inheritance-type overriding, instead we need
    # to literally overwrite Mongrel's method and replace it with our own.
    # Very graceful.  But it works.
    alias _can_serve can_serve

    # This method is called by Mongrel::RailsHandler to see if mongrel can
    # get away with just serving up a file instead of invoking Rails.  It
    # returns nil if it can't, and returns the filename if it can.
    def can_serve(file)
      # First let Mongrel decide if it can serve the file, then check to see
      # if we're controlling permissions on it next.
      if (file = _can_serve(file)) && FilePermissions.pattern.match(file)
        return nil
      else
        return file
      end
    end
  end
end

class FilePermissions

  # Look up the MIME type of a file, returns it as a string.  Raises a
  # RuntimeError if it can't find it.  Returns a string.  Example: 
  #   mime = FilePermissions.mime_type("image.jpg")
  #   # mime = "image/jpeg"
  def self.mime_type(file)
    raise(RuntimeError, "Don't know the MIME type of #{file}.")\
      if !(match = file.match(/(\.\w+)$/)) ||
         !(mime = Mongrel::DirHandler::MIME_TYPES[match[1]])
         # (had to use Mongrel's list because Rails's list is useless)
    return mime
  end
end