Reland: Refactor current GAE abstraction library to be free of the SDK*

go/src/infra/gae/libs/gae/helper/generic_key.go

Index: go/src/infra/gae/libs/gae/helper/generic_key.go
diff --git a/go/src/infra/gae/libs/gae/helper/generic_key.go b/go/src/infra/gae/libs/gae/helper/generic_key.go
new file mode 100644
index 0000000000000000000000000000000000000000..892e2c32121d70e74013b3025f758db70334ddc3
--- /dev/null
+++ b/go/src/infra/gae/libs/gae/helper/generic_key.go
@@ -0,0 +1,84 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package helper
+
+import (
+	"encoding/json"
+	"infra/gae/libs/gae"
+)
+
+// GenericDSKey is an implementation of gae.DSKey which doesn't rely on the
+// SDK's implementation. It differs slightly in that it's not recursive (and
+// thus cannot express some of the invalid Key's that the SDK implementation
+// can). In particular, it's not possible to have a GenericDSKey in a namespace
+// whose Parent() is in a different namespace.
+//
+// GenericDSKey also implements json.Marshaler and json.Unmarshaler so it's
+// suitable for use in structs which need to serialize both to json and to
+// datastore.
+type GenericDSKey struct {
+	appID     string
+	namespace string
+	toks      []gae.DSKeyTok
+}
+
+var _ interface {
+	gae.DSKey
+	json.Marshaler
+	json.Unmarshaler
+} = (*GenericDSKey)(nil)
+
+// NewDSKeyToks creates a new GenericDSKey. It is the DSKey implementation
+// returned from the various DSPropertyMap serialization routines, as well as
+// the native key implementation for the in-memory implementation of gae.
+func NewDSKeyToks(appID, ns string, toks []gae.DSKeyTok) *GenericDSKey {
+	newToks := make([]gae.DSKeyTok, len(toks))
+	copy(newToks, toks)
+	return &GenericDSKey{appID, ns, newToks}
+}
+
+// NewDSKey is a wrapper around NewDSKeyToks which has an interface similar
+// to NewKey in the SDK.
+func NewDSKey(appID, ns, kind, stringID string, intID int64, parent gae.DSKey) *GenericDSKey {
+	_, _, toks := DSKeySplit(parent)
+	newToks := make([]gae.DSKeyTok, len(toks))
+	copy(newToks, toks)
+	newToks = append(newToks, gae.DSKeyTok{Kind: kind, StringID: stringID, IntID: intID})
+	return &GenericDSKey{appID, ns, newToks}
+}
+
+func (k *GenericDSKey) lastTok() (ret gae.DSKeyTok) {
+	if len(k.toks) > 0 {
+		ret = k.toks[len(k.toks)-1]
+	}
+	return
+}
+
+func (k *GenericDSKey) AppID() string     { return k.appID }
+func (k *GenericDSKey) Namespace() string { return k.namespace }
+func (k *GenericDSKey) Kind() string      { return k.lastTok().Kind }
+func (k *GenericDSKey) StringID() string  { return k.lastTok().StringID }
+func (k *GenericDSKey) IntID() int64      { return k.lastTok().IntID }
+func (k *GenericDSKey) String() string    { return DSKeyString(k) }
+
+func (k *GenericDSKey) MarshalJSON() ([]byte, error) {
+	return DSKeyMarshalJSON(k)
+}
+
+func (k *GenericDSKey) UnmarshalJSON(buf []byte) error {
+	appID, namespace, toks, err := DSKeyUnmarshalJSON(buf)
+	if err != nil {
+		return err
+	}
+	*k = *NewDSKeyToks(appID, namespace, toks)
+	return nil
+}
+
+func (k *GenericDSKey) Parent() gae.DSKey {
+	if len(k.toks) <= 1 {
+		return nil
+	}
+	return &GenericDSKey{k.appID, k.namespace, k.toks[:len(k.toks)-1]}
+}