Merge pull request #190 from rubychan/autoload

Cleanup Folder structure

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