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

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

Index: go/src/infra/gae/libs/gae/helper/shell_key.go
diff --git a/go/src/infra/gae/libs/gae/helper/shell_key.go b/go/src/infra/gae/libs/gae/helper/shell_key.go
new file mode 100644
index 0000000000000000000000000000000000000000..001e9bde8c8120f5d2d00c4e247e77ccc8ba9694
--- /dev/null
+++ b/go/src/infra/gae/libs/gae/helper/shell_key.go
@@ -0,0 +1,58 @@
+// 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 (
+	"infra/gae/libs/gae"
+)
+
+type shellDSKey struct {

[Vadim Sh., 2015/07/13 21:17:12]

what does "shell" stand for?

[iannucci, 2015/07/13 22:39:52]

it's.. not a very good name. I'll change it. Made it public as well, since it's
useful to have a concrete type.

+	appID     string
+	namespace string
+	toks      []gae.DSKeyTok
+}
+
+var _ gae.DSKey = (*shellDSKey)(nil)
+
+// NewDSKeyToks creates a a reference implementation of gae.DSKey. 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) gae.DSKey {
+	newToks := make([]gae.DSKeyTok, len(toks))
+	copy(newToks, toks)

[Vadim Sh., 2015/07/13 21:17:12]

nit: newToks := append(nil, toks...)? :) It's probably smart enough to
preallocate the array.

Also, why copy? DKKeyTok is supposed to be immutable. Avoiding copy will make
.Parent() a bit faster (and .Parent() is used very often).

[iannucci, 2015/07/13 22:39:52]

I guess I'm just paranoid of re-using the slice because the caller technically
has pointers to all the stuff inside of it (and who knows where the caller got
the slice from in the first place). The SDK implementation uses a
pseudo-linked-list for this (e.g. every key is a token with a copy of
appid+namespace and a pointer to the parent).

However, since I copy it here, I don't need to copy it in Parent.

+	return &shellDSKey{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) gae.DSKey {
+	_, _, toks := DSKeySplit(parent)
+	newToks := make([]gae.DSKeyTok, len(toks))
+	copy(newToks, toks)
+	newToks = append(newToks, gae.DSKeyTok{Kind: kind, StringID: stringID, IntID: intID})
+	return &shellDSKey{appID, ns, newToks}
+}
+
+func (k *shellDSKey) lastTok() (ret gae.DSKeyTok) {
+	if len(k.toks) > 0 {
+		ret = k.toks[len(k.toks)-1]
+	}
+	return
+}
+
+func (k *shellDSKey) AppID() string     { return k.appID }
+func (k *shellDSKey) Namespace() string { return k.namespace }
+func (k *shellDSKey) Kind() string      { return k.lastTok().Kind }
+func (k *shellDSKey) StringID() string  { return k.lastTok().StringID }
+func (k *shellDSKey) IntID() int64      { return k.lastTok().IntID }
+func (k *shellDSKey) String() string    { return DSKeyString(k) }
+
+func (k *shellDSKey) Parent() gae.DSKey {
+	if len(k.toks) <= 1 {
+		return nil
+	}
+	return NewDSKeyToks(k.appID, k.namespace, k.toks[:len(k.toks)-1])
+}