[UNSTABLE] Wrote JSONClimber to simplify sequence migrations.

app/lib/celery_script/json_climber.rb

@@ -0,0 +1,38 @@
+module CeleryScript
+  # THIS IS A MORE MINIMAL VERSION OF CeleryScript::TreeClimber.
+  # It is a NON-VALIDATING tree climber.
+  # Don't use this on unverified data structures.
+  class JSONClimber
+    HASH_ONLY = "Expected a Hash."
+    NOT_NODE  = "Expected hash with atleast a `kind` and `args` prop."
+
+    def self.climb(thing, &callable)
+      raise HASH_ONLY unless thing.is_a?(Hash)
+      raise NOT_NODE  unless is_node?(thing)
+      go(thing, callable)
+      thing
+    rescue => q
+      binding.pry
+    end
+
+  private
+
+    def self.is_node?(maybe)
+      maybe.is_a?(Hash) &&
+      maybe.keys.include?(:kind) &&
+      maybe.keys.include?(:args)
+    end
+
+    def self.go(thing, callable)
+      if is_node?(thing)
+        callable.call(thing)
+
+        # Recurse into each arg
+        thing[:args].map { |x| go(x.last, callable) }
+
+        # Maybe recurse into body.
+        (thing[:body] || []).each { |x| go(x, callable) }
+      end
+    end
+  end
+end

app/lib/sequence_migration.rb

@@ -28,7 +28,8 @@ module SequenceMigration
         AddVersionInfo,
         UpdateChannelNames,
         AddToolsToMoveAbs,
-        UpdateIfStatement
+        UpdateIfStatement,
+        CleanupArgNames
       ]
     end
 

app/lib/sequence_migration/cleanup_arg_names.rb

@@ -0,0 +1,19 @@
+module SequenceMigration
+  # Background:
+  # This is a refactor of what once was called the `if_statement` block:
+  # * Added a `nothing` node type (sorry, we actually need it now).
+  # * if_statement becomes _if
+  # * sub_sequence_id becomes _then
+  # * Add _else arg to _if.
+  # * _then/_else expect a execute or nothing node instead of a number.
+  class CleanupArgNames < Base
+    VERSION    = 4
+    CREATED_ON = "January 5 2017"
+
+    def up
+      sequence.traverse do |node|
+        puts node[:kind]
+      end
+    end
+  end
+end

app/models/sequence.rb

@@ -45,4 +45,12 @@ class Sequence < ActiveRecord::Base
   def self.random
     Sequence.order("RANDOM()").first
   end
+
+  def traverse(&blk)
+    hash = as_json
+      .tap { |x| x[:kind] = "sequence" }
+      .deep_symbolize_keys
+      .slice(:kind, :args, :body)
+    CeleryScript::JSONClimber.climb(hash, &blk)
+  end
 end