filters: initial implementation

1 files changed, 80 insertions, 0 deletions

diff --git a/lib/rbot/core/utils/filters.rb b/lib/rbot/core/utils/filters.rb
new file mode 100644
index 00000000..5744b732
--- /dev/null
+++ b/lib/rbot/core/utils/filters.rb
@@ -0,0 +1,80 @@
+#-- vim:sw=2:et
+#++
+#
+# :title: Stream filters
+#
+# Author:: Giuseppe "Oblomov" Bilotta <giuseppe.bilotta@gmail.com>
+# Copyright:: (C) 2008 Giuseppe Bilotta
+# License:: GPL v2
+#
+# This file collects methods to handle 'stream filters', a generic mechanism
+# to transform text+attributes into other text+attributes
+
+module ::Irc
+  class Bot
+
+    # The DataStream class. A DataStream is just a Hash. The :text key has
+    # a special meaning because it's the value that will be used when
+    # converting to String
+    class DataStream < Hash
+
+      def initialize(hsh={})
+        self.replace(hsh)
+      end
+
+      # Returns the :text key
+      def to_s
+        return self[:text]
+      end
+    end
+
+    # The DataFilter class. A DataFilter is a wrapper around a block
+    # that can be run on a DataStream to process it. The block is supposed to
+    # return another DataStream object
+    class DataFilter
+      def initialize(&block)
+        raise "No block provided" unless block_given?
+        @block = block
+      end
+
+      def call(stream)
+        @block.call(stream)
+      end
+      alias :run :call
+      alias :filter :call
+    end
+
+    # This method processes the DataStream _stream_ with the filters _name_.
+    # _name_ can be either a single Symbol (filter name), or an Array of
+    # Symbols, in which case the output of each filter will be used as input
+    # for the next
+    #
+    def filter(name, stream={})
+      @filters ||= {}
+      names = (Symbol === name ? [name] : name.dup)
+      ds = (DataStream === stream ? stream : DataStream.new(stream))
+      return ds if names.empty?
+      # check if filters exist
+      missing = names - @filters.keys
+      raise "Missing filters: #{missing.join(', ')}" unless missing.empty?
+      fs = @filters.values_at(*names)
+      fs.inject(ds) { |mid, f| mid = f.call(mid) }
+    end
+
+    # This method is used to register a new filter
+    def register_filter(name, &block)
+      raise "No block provided" unless block_given?
+      @filters ||= {}
+      @filters[name.to_sym] = DataFilter.new &block
+    end
+
+    # This method clears the filter list and installs the identity filter
+    def clear_filters
+      @filters ||= {}
+      @filters.clear
+      register_filter(:identity) { |stream| stream }
+    end
+  end
+end
+
+