Initial distributor implementation

appengine/cmd/dm/mutate/merge_quest.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package mutate
 
 import (
         "github.com/luci/gae/service/datastore"
         "github.com/luci/luci-go/appengine/cmd/dm/model"
         "github.com/luci/luci-go/appengine/tumble"
         "github.com/luci/luci-go/common/logging"
         "golang.org/x/net/context"
 )
 
 // MergeQuest ensures that the given Quest exists and contains the merged
 // set of BuiltBy entries.
 type MergeQuest struct {
-        Quest *model.Quest
+        Quest   *model.Quest
+        AndThen []tumble.Mutation
 }
 
 // Root implements tumble.Mutation.
 func (m *MergeQuest) Root(c context.Context) *datastore.Key {
-        return datastore.Get(c).KeyForObj(m.Quest)
+        return model.QuestKeyFromID(c, m.Quest.ID)
 }
 
 // RollForward implements tumble.Mutation.
 func (m *MergeQuest) RollForward(c context.Context) (muts []tumble.Mutation, err error) {
         ds := datastore.Get(c)
 
-        curQuest := &model.Quest{ID: m.Quest.ID}
+        curQuest := model.QuestFromID(m.Quest.ID)
 
         c = logging.SetField(c, "qid", m.Quest.ID)
 
         reason := "getting quest"
         switch err = ds.Get(curQuest); err {
         case nil:
                 prevLen := len(curQuest.BuiltBy)
                 curQuest.BuiltBy.Add(m.Quest.BuiltBy...)
                 if len(curQuest.BuiltBy) > prevLen {
                         reason = "putting merged quest"
                         err = ds.Put(curQuest)
                 }
         case datastore.ErrNoSuchEntity:
                 reason = "putting quest"
                 err = ds.Put(m.Quest)
         }
 
         if err != nil {
                 logging.WithError(err).Errorf(c, "%s", reason)
         }
 
+        muts = m.AndThen
+
         return
 }
 
 func init() {
         tumble.Register((*MergeQuest)(nil))
 }