Prepare EtcdHelper to extract more data from Node

In order to support graceful deletion, the resource object will
need access to the TTL value in etcd.  Also, in the future we
may want to get the creation index (distinct from modifiedindex)
and expose it to clients.  Change EtcdResourceVersioner to be
more type specific (objects vs lists) and provide a default
implementation that relies on the internal API convention.

Also, rename etcd_tools.go to etcd_helper.go and split a few
things up.

pkg/tools/etcd_object.go

@@ -0,0 +1,74 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package tools
+
+import (
+	"strconv"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
+	"github.com/coreos/go-etcd/etcd"
+)
+
+// APIObjectVersioner implements versioning and extracting etcd node information
+// for objects that have an embedded ObjectMeta or ListMeta field.
+type APIObjectVersioner struct{}
+
+// UpdateObject implements EtcdVersioner
+func (a APIObjectVersioner) UpdateObject(obj runtime.Object, node *etcd.Node) error {
+	objectMeta, err := api.ObjectMetaFor(obj)
+	if err != nil {
+		return err
+	}
+	version := node.ModifiedIndex
+	versionString := ""
+	if version != 0 {
+		versionString = strconv.FormatUint(version, 10)
+	}
+	objectMeta.ResourceVersion = versionString
+	return nil
+}
+
+// UpdateList implements EtcdVersioner
+func (a APIObjectVersioner) UpdateList(obj runtime.Object, resourceVersion uint64) error {
+	listMeta, err := api.ListMetaFor(obj)
+	if err != nil || listMeta == nil {
+		return err
+	}
+	versionString := ""
+	if resourceVersion != 0 {
+		versionString = strconv.FormatUint(resourceVersion, 10)
+	}
+	listMeta.ResourceVersion = versionString
+	return nil
+}
+
+// ObjectResourceVersion implements EtcdVersioner
+func (a APIObjectVersioner) ObjectResourceVersion(obj runtime.Object) (uint64, error) {
+	meta, err := api.ObjectMetaFor(obj)
+	if err != nil {
+		return 0, err
+	}
+	version := meta.ResourceVersion
+	if len(version) == 0 {
+		return 0, nil
+	}
+	return strconv.ParseUint(version, 10, 64)
+}
+
+// APIObjectVersioner implements EtcdVersioner
+var _ EtcdVersioner = APIObjectVersioner{}