module CodeRay::PluginHost

def [] id, *args, &blk
  plugin = validate_id(id)
  begin
    plugin = plugin_hash.[](plugin, *args, &blk)
  end while plugin.is_a? String
  plugin
end

def all_plugins
  load_all
  plugin_hash.values.grep(Class)
end

def const_missing const
  id = const.to_s.
    gsub(/([A-Z]+)([A-Z][a-z])/,'\1_\2').
    gsub(/([a-z\d])([A-Z])/,'\1_\2').
    downcase
  load id
end

def default id = nil
  if id
    id = validate_id id
    raise "The default plugin can't be named \"default\"." if id == :default
    plugin_hash[:default] = id
  else
    load :default
  end
end

def extended mod
  PLUGIN_HOSTS << mod
end

def list
  Dir[path_to('*')].select do |file|
    File.basename(file)[/^(?!_)\w+\.rb$/]
  end.map do |file|
    File.basename(file, '.rb').to_sym
  end
end

def load_all
  for plugin in list
    load plugin
  end
end

def load_plugin_map
  mapfile = path_to '_map'
  if File.exist? mapfile
    require mapfile
    true
  else
    false
  end
end

def make_plugin_hash
  Hash.new do |h, plugin_id|
    id = validate_id(plugin_id)
    path = path_to id
    begin
      require path
    rescue LoadError => boom
      if h.has_key?(:default)
        h[:default]
      else
        raise PluginNotFound, '%p could not load plugin %p: %s' % [self, id, boom]
      end
    else
      # Plugin should have registered by now
      if h.has_key? id
        h[id]
      else
        raise PluginNotFound, "No #{self.name} plugin for #{id.inspect} found in #{path}."
      end
    end
  end
end

def map hash
  for from, to in hash
    from = validate_id from
    to   = validate_id to
    plugin_hash[from] = to unless plugin_hash.has_key? from
  end
end

def path_to plugin_id
  File.join plugin_path, "#{plugin_id}.rb"
end

def plugin_hash
  @plugin_hash ||= (@plugin_hash = make_plugin_hash).tap { load_plugin_map }
end

def plugin_path *args
  unless args.empty?
    @plugin_path = File.expand_path File.join(*args)
  end
  @plugin_path ||= ''
end

def register plugin, id
  plugin_hash[validate_id(id)] = plugin
end

def validate_id id
  case id
  when Symbol
    id.to_s
  when String
    if id[/\w+/] == id
      id.downcase
    else
      raise ArgumentError, "Invalid id given: #{id}"
    end
  else
    raise ArgumentError, "Symbol or String expected, but #{id.class} given."
  end
end