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Diffstat (limited to 'lib/coderay/helpers/plugin_host.rb')
| -rw-r--r-- | lib/coderay/helpers/plugin_host.rb | 221 |
1 files changed, 221 insertions, 0 deletions
diff --git a/lib/coderay/helpers/plugin_host.rb b/lib/coderay/helpers/plugin_host.rb new file mode 100644 index 0000000..e9bc17c --- /dev/null +++ b/lib/coderay/helpers/plugin_host.rb @@ -0,0 +1,221 @@ +module CodeRay + + # = PluginHost + # + # A simple subclass/subfolder plugin system. + # + # Example: + # class Generators + # extend PluginHost + # plugin_path 'app/generators' + # end + # + # class Generator + # extend Plugin + # PLUGIN_HOST = Generators + # end + # + # class FancyGenerator < Generator + # register_for :fancy + # end + # + # Generators[:fancy] #-> FancyGenerator + # # or + # CodeRay.require_plugin 'Generators/fancy' + # # or + # Generators::Fancy + module PluginHost + + # Raised if Encoders::[] fails because: + # * a file could not be found + # * the requested Plugin is not registered + PluginNotFound = Class.new LoadError + HostNotFound = Class.new LoadError + + PLUGIN_HOSTS = [] + PLUGIN_HOSTS_BY_ID = {} # dummy hash + + # Loads all plugins using list and load. + def load_all + for plugin in list + load plugin + end + end + + # Returns the Plugin for +id+. + # + # Example: + # yaml_plugin = MyPluginHost[:yaml] + def [] id, *args, &blk + plugin = validate_id(id) + begin + plugin = plugin_hash.[](plugin, *args, &blk) + end while plugin.is_a? String + plugin + end + + alias load [] + + # Tries to +load+ the missing plugin by translating +const+ to the + # underscore form (eg. LinesOfCode becomes lines_of_code). + 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 + + class << self + + # Adds the module/class to the PLUGIN_HOSTS list. + def extended mod + PLUGIN_HOSTS << mod + end + + end + + # The path where the plugins can be found. + def plugin_path *args + unless args.empty? + @plugin_path = File.expand_path File.join(*args) + end + @plugin_path ||= '' + end + + # Map a plugin_id to another. + # + # Usage: Put this in a file plugin_path/_map.rb. + # + # class MyColorHost < PluginHost + # map :navy => :dark_blue, + # :maroon => :brown, + # :luna => :moon + # 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 + + # Define the default plugin to use when no plugin is found + # for a given id, or return the default plugin. + # + # See also map. + # + # class MyColorHost < PluginHost + # map :navy => :dark_blue + # default :gray + # end + # + # MyColorHost.default # loads and returns the Gray plugin + 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 + + # Every plugin must register itself for +id+ by calling register_for, + # which calls this method. + # + # See Plugin#register_for. + def register plugin, id + plugin_hash[validate_id(id)] = plugin + end + + # A Hash of plugion_id => Plugin pairs. + def plugin_hash + @plugin_hash ||= (@plugin_hash = make_plugin_hash).tap { load_plugin_map } + end + + # Returns an array of all .rb files in the plugin path. + # + # The extension .rb is not included. + 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 + + # Returns an array of all Plugins. + # + # Note: This loads all plugins using load_all. + def all_plugins + load_all + plugin_hash.values.grep(Class) + end + + # Loads the map file (see map). + # + # This is done automatically when plugin_path is called. + def load_plugin_map + mapfile = path_to '_map' + if File.exist? mapfile + require mapfile + true + else + false + end + end + + protected + + # Return a plugin hash that automatically loads plugins. + 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 + + # Returns the expected path to the plugin file for the given id. + def path_to plugin_id + File.join plugin_path, "#{plugin_id}.rb" + end + + # Converts +id+ to a valid plugin ID String, or returns +nil+. + # + # Raises +ArgumentError+ for all other objects, or if the + # given String includes non-alphanumeric characters (\W). + 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 + + end + +end |