(experimental) added framework for filtering all sorts of internals in discourse and consuming by plugins

app/models/post.rb

@@ -6,6 +6,7 @@ require_dependency 'enum'
 require_dependency 'trashable'
 require_dependency 'post_analyzer'
 require_dependency 'validators/post_validator'
+require_dependency 'plugin/filter'
 
 require 'archetype'
 require 'digest/sha1'
@@ -108,7 +109,7 @@ class Post < ActiveRecord::Base
   end
 
   def cook(*args)
-    post_analyzer.cook(*args)
+    Plugin::Filter.apply(:after_post_cook, self, post_analyzer.cook(*args))
   end
 
 

lib/plugin/filter.rb

@@ -0,0 +1,18 @@
+require_dependency 'plugin/filter_manager'
+# this concept is borrowed straight out of wordpress
+module Plugin
+  class Filter
+    def self.manager
+      @manager ||= FilterManager.new
+    end
+
+    def self.register(name, &blk)
+      manager.register(name, &blk)
+    end
+
+    def self.apply(name, context, result)
+      manager.apply(name, context, result)
+    end
+
+  end
+end

lib/plugin/filter_manager.rb

@@ -0,0 +1,23 @@
+module Plugin
+  class FilterManager
+
+    def initialize
+      @map = {}
+    end
+
+    def register(name, &blk)
+      raise ArgumentException unless blk && blk.arity == 2
+      filters = @map[name] ||= []
+      filters << blk
+    end
+
+    def apply(name, context, result)
+      if filters = @map[name]
+        filters.each do |blk|
+          result = blk.call(context, result)
+        end
+      end
+      result
+    end
+  end
+end

spec/components/plugin/filter_manager_spec.rb

@@ -0,0 +1,35 @@
+require 'spec_helper'
+require_dependency 'plugin/filter_manager'
+
+describe Plugin::FilterManager do
+  let(:instance){ Plugin::FilterManager.new }
+
+  it "calls registered filters correctly" do
+    instance.register(:added_numbers) do |context,result|
+      context + result + 1
+    end
+
+    instance.register(:added_numbers) do |context,result|
+      context + result + 2
+    end
+
+    instance.apply(:added_numbers, 1, 0).should == 5
+  end
+
+  it "should raise an exception if wrong arity is passed in" do
+    lambda do
+      instance.register(:test) do
+      end
+    end.should raise_exception
+  end
+
+  it "should return the original if no filters exist" do
+    instance.apply(:foo, nil, 42).should == 42
+  end
+
+  it "should raise an exception if no block is passed in" do
+    lambda do
+      instance.register(:test)
+    end.should raise_exception
+  end
+end