Introduce 'post' and 'pre' commands

Both post and pre are called after all 'cmd' are already called, but
output from 'pre' is put on top of configuration output and output from
'post' is put on bottom of confguration output.

Rationale is dynamic configuration, where you'll only know after running
some commands what commands you want to run.

Both except blocks, such as

pre do
  # commands to execute
end

Both can be called multiple times

2 files changed, 42 insertions, 6 deletions

diff --git a/lib/oxidized/model/junos.rb b/lib/oxidized/model/junos.rb
index a7080e1..4bca998 100644
--- a/lib/oxidized/model/junos.rb
+++ b/lib/oxidized/model/junos.rb
@@ -19,7 +19,7 @@ class JunOS < Oxidized::Model
     comment cfg
   end
 
-  def main
+  post do
     case @model
     when 'mx960'
       cmd('show chassis fabric reachability')  { |cfg| comment cfg }
diff --git a/lib/oxidized/model/model.rb b/lib/oxidized/model/model.rb
index f95443d..70b307f 100644
--- a/lib/oxidized/model/model.rb
+++ b/lib/oxidized/model/model.rb
@@ -2,8 +2,9 @@ module Oxidized
   class Model
     class << self
       def inherited klass
-        klass.instance_variable_set '@cmd',    Hash.new { |h,k| h[k] = [] }
-        klass.instance_variable_set '@cfg',    Hash.new { |h,k| h[k] = [] }
+        klass.instance_variable_set '@cmd',   Hash.new { |h,k| h[k] = [] }
+        klass.instance_variable_set '@cfg',   Hash.new { |h,k| h[k] = [] }
+        klass.instance_variable_set '@procs', Hash.new { |h,k| h[k] = [] }
         klass.instance_variable_set '@expect', []
         klass.const_set :CFG, CFG
         Oxidized.mgr.loader = { :class => klass }
@@ -39,6 +40,35 @@ module Oxidized
       def expects
         @expect
       end
+
+      # calls the block at the end of the model, prepending the output of the
+      # block to the output string
+      #
+      # @author Saku Ytti <saku@ytti.fi>
+      # @since 0.0.39
+      # @yield expects block which should return [String]
+      # @return [void]
+      def pre &block
+        @procs[:pre] << block
+      end
+
+      # calls the block at the end of the model, adding the output of the block
+      # to the output string
+      #
+      # @author Saku Ytti <saku@ytti.fi>
+      # @since 0.0.39
+      # @yield expects block which should return [String]
+      # @return [void]
+      def post &block
+        @procs[:post] << block
+      end
+
+      # @author Saku Ytti <saku@ytti.fi>
+      # @since 0.0.39
+      # @return [Hash] hash proc procs :pre+:post to be prepended/postfixed to output
+      def procs
+        @procs
+      end
     end
 
     attr_accessor :input
@@ -87,14 +117,20 @@ module Oxidized
     end
 
     def get
-      data = ''
+      data, pre = '', ''
+      procs = self.class.procs
       self.class.cmds[:cmd].each do |command, block|
         out = cmd command, &block
         return false unless out
         data << out.to_s
       end
-      data << main.to_s if respond_to? :main
-      data
+      procs[:pre].each do |pre_proc|
+        pre << instance_eval(&pre_proc)
+      end
+      procs[:post].each do |post_proc|
+        data << instance_eval(&post_proc)
+      end
+      pre + data
     end
 
     def comment _comment