From e4f56866aa9dc11f2a9563e7a0a0e0a9e6cbcd85 Mon Sep 17 00:00:00 2001
From: Jamis Buck <jamis@37signals.com>
Date: Sat, 18 Feb 2006 22:09:05 +0000
Subject: [PATCH] Add extension mechanism for custom ST operations

git-svn-id: http://svn.rubyonrails.org/rails/tools/switchtower@3604 5ecf4fe2-1ee6-0310-87b1-e25e094e27de
---
 CHANGELOG                        |  2 ++
 lib/switchtower/configuration.rb |  1 +
 lib/switchtower/extensions.rb    | 38 ++++++++++++++++++++++++++++++++
 test/actor_test.rb               | 16 ++++++++++++++
 4 files changed, 57 insertions(+)
 create mode 100644 lib/switchtower/extensions.rb

diff --git a/CHANGELOG b/CHANGELOG
index e705788f..cf0ac21a 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,7 @@
 *0.11.0* *SVN*
 
+* Add extension mechanism for custom ST operations
+
 * Make ST rails rake tasks more configurable
 
 * Add Actor#current_task and simplify Task#servers
diff --git a/lib/switchtower/configuration.rb b/lib/switchtower/configuration.rb
index 53dfa0d8..57916123 100644
--- a/lib/switchtower/configuration.rb
+++ b/lib/switchtower/configuration.rb
@@ -1,6 +1,7 @@
 require 'switchtower/actor'
 require 'switchtower/logger'
 require 'switchtower/scm/subversion'
+require 'switchtower/extensions'
 
 module SwitchTower
   # Represents a specific SwitchTower configuration. A Configuration instance
diff --git a/lib/switchtower/extensions.rb b/lib/switchtower/extensions.rb
new file mode 100644
index 00000000..e6e0929b
--- /dev/null
+++ b/lib/switchtower/extensions.rb
@@ -0,0 +1,38 @@
+require 'switchtower/actor'
+
+module SwitchTower
+  class ExtensionProxy
+    def initialize(actor, mod)
+      @actor = actor
+      extend(mod)
+    end
+
+    def method_missing(sym, *args, &block)
+      @actor.send(sym, *args, &block)
+    end
+  end
+
+  EXTENSIONS = {}
+
+  def self.plugin(name, mod)
+    return false if EXTENSIONS.has_key?(name)
+
+    SwitchTower::Actor.class_eval <<-STR, __FILE__, __LINE__+1
+      def #{name}
+        @__#{name}_proxy ||= SwitchTower::ExtensionProxy.new(self, SwitchTower::EXTENSIONS[#{name.inspect}])
+      end
+    STR
+
+    EXTENSIONS[name] = mod
+    return true
+  end
+
+  def self.remove_plugin(name)
+    if EXTENSIONS.delete(name)
+      SwitchTower::Actor.send(:remove_method, name)
+      return true
+    end
+
+    return false
+  end
+end
\ No newline at end of file
diff --git a/test/actor_test.rb b/test/actor_test.rb
index 3cb424d7..371abc80 100644
--- a/test/actor_test.rb
+++ b/test/actor_test.rb
@@ -84,6 +84,12 @@ class ActorTest < Test::Unit::TestCase
     end
   end
 
+  module CustomExtension
+    def do_something_extra(a, b, c)
+      run "echo '#{a} :: #{b} :: #{c}'"
+    end
+  end
+
   def setup
     TestingCommand.reset!
     @actor = TestActor.new(MockConfiguration.new)
@@ -275,4 +281,14 @@ class ActorTest < Test::Unit::TestCase
 
     assert_raises(RuntimeError) { @actor.foo }
   end
+
+  def test_custom_extension
+    assert SwitchTower.plugin(:custom, CustomExtension)
+    @actor.define_task :foo, :roles => :db do
+      custom.do_something_extra(1, 2, 3)
+    end
+    assert_nothing_raised { @actor.foo }
+    assert TestingCommand.invoked?
+    assert SwitchTower.remove_plugin(:custom)
+  end
 end