require 'name_utils'

class OneInstancePluginLoader
   attr_reader :baseClass, :pluginDir, :classes

   def initialize (baseClass, dir)
      @pluginDir = dir
      @baseClass = baseClass
      @classes   = Hash.new

      if baseClass.kind_of? String
         className  = baseClass.gsub('^([a-zA-Z]+).*', '\1')
         @baseClass = eval className
      end
   end

   def avail_plugins
      list = Array.new
      Dir.open(@pluginDir).each do |f|
         list << NameUtils.filename_to_class(f) unless f =~ /^\./
      end
      list
   end

=begin
   --- plugin (c)

   Returns an object of the type ((|c|)). It loads the class if necessary.
=end

   def plugin (c)
      return @classes[c] if @classes[c]

      fileName = NameUtils.class_to_filename c

      begin
         require pluginDir + '/' + fileName
         safeClassname = eval(c.gsub('^([a-zA-Z]+).*', '\1'))
      rescue LoadError
         raise "Can't find plugin #{c} (file '#{fileName}'). Hint: Bad classname?"
      end

      obj = safeClassname.new
      raise "#{c} is not a #{@baseClass} type plugin" unless obj.kind_of? @baseClass
      @classes[c] = obj
   end

=begin
   --- plugin_by_index (i)

   Returns an object of the type of the plugin whose index in the
   avail_plugins array is ((|i|)). It loads the class if necessary.
=end

   def plugin_by_index (i)
      plugin(avail_plugins[i])
   end
end