2 files changed, 106 insertions, 0 deletions
diff --git a/lib/puppet/network/format_handler.rb b/lib/puppet/network/format_handler.rb
new file mode 100644
index 000000000..a69c29232
--- /dev/null
+++ b/lib/puppet/network/format_handler.rb
@@ -0,0 +1,33 @@
+require 'puppet/network'
+
+module Puppet::Network::FormatHandler
+    def self.extended(klass)
+        klass.extend(ClassMethods)
+
+        # LAK:NOTE This won't work in 1.9 ('send' won't be able to send
+        # private methods, but I don't know how else to do it.
+        klass.send(:include, InstanceMethods)
+    end
+
+    module ClassMethods
+        def convert_from(format, data)
+            raise ArgumentError, "Format %s not supported" % format unless support_format?(format)
+            send("from_%s" % format, data)
+        end
+
+        def support_format?(name)
+            respond_to?("from_%s" % name) and instance_methods.include?("to_%s" % name)
+        end
+    end
+
+    module InstanceMethods
+        def render(format)
+            raise ArgumentError, "Format %s not supported" % format unless support_format?(format)
+            send("to_%s" % format)
+        end
+
+        def support_format?(name)
+            self.class.support_format?(name)
+        end
+    end
+end
diff --git a/spec/unit/network/format_handler.rb b/spec/unit/network/format_handler.rb
new file mode 100755
index 000000000..ab863fc8e
--- /dev/null
+++ b/spec/unit/network/format_handler.rb
@@ -0,0 +1,73 @@
+#!/usr/bin/env ruby
+
+require File.dirname(__FILE__) + '/../../spec_helper'
+
+require 'puppet/network/format_handler'
+
+class FormatTester
+    extend Puppet::Network::FormatHandler
+
+    def self.from_good
+    end
+
+    def to_good
+    end
+end
+
+describe Puppet::Network::FormatHandler do
+    it "should be able to test whether a format is supported" do
+        FormatTester.should respond_to(:support_format?)
+    end
+
+    it "should consider the format supported if it can convert from an instance to the format and from the format to an instance" do
+        FormatTester.should be_support_format(:good)
+    end
+
+    it "should not consider the format supported unless it can convert from an instance to the format and from the format to an instance" do
+        FormatTester.should_not be_support_format(:nope)
+    end
+
+    it "should be able to convert from a given format" do
+        FormatTester.should respond_to(:convert_from)
+    end
+
+    it "should fail if asked to convert from an unsupported format" do
+        FormatTester.expects(:support_format?).with(:nope).returns false
+        lambda { FormatTester.convert_from(:nope, "mydata") }.should raise_error(ArgumentError)
+    end
+
+    it "should call the format-specific converter when asked to convert from a given format" do
+        FormatTester.expects(:from_good).with("mydata")
+        FormatTester.convert_from(:good, "mydata")
+    end
+
+    describe "when an instance" do
+        it "should be able to test whether a format is supported" do
+            FormatTester.new.should respond_to(:support_format?)
+        end
+
+        it "should consider the format supported if it can convert from an instance to the format and from the format to an instance" do
+            FormatTester.new.should be_support_format(:good)
+        end
+
+        it "should not consider the format supported unless it can convert from an instance to the format and from the format to an instance" do
+            FormatTester.new.should_not be_support_format(:nope)
+        end
+
+        it "should be able to convert to a given format" do
+            FormatTester.new.should respond_to(:render)
+        end
+
+        it "should fail if asked to convert to an unsupported format" do
+            tester = FormatTester.new
+            tester.expects(:support_format?).with(:nope).returns false
+            lambda { tester.render(:nope) }.should raise_error(ArgumentError)
+        end
+
+        it "should call the format-specific converter when asked to convert to a given format" do
+            tester = FormatTester.new
+            tester.expects(:to_good)
+            tester.render(:good)
+        end
+    end
+end