Add cloud datastore implementation.

impl/cloud/info.go

Index: impl/cloud/info.go
diff --git a/impl/cloud/info.go b/impl/cloud/info.go
new file mode 100644
index 0000000000000000000000000000000000000000..ed30700f9138dc7dff73da4e193008b112de88a1
--- /dev/null
+++ b/impl/cloud/info.go
@@ -0,0 +1,104 @@
+// Copyright 2016 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 cloud
+
+import (
+	"errors"
+	"time"
+
+	infoS "github.com/luci/gae/service/info"
+
+	"golang.org/x/net/context"
+)
+
+var errNotImplemented = errors.New("not implemented")
+
+// cloudInfo is a reconstruction of the info service for the cloud API.
+//
+// It will return information sufficent for datastore operation.
+type infoState struct {
+	// namespace is the current namesapce, or the empty string for no namespace.
+	namespace string
+}
+
+var infoStateKey = "*cloud.infoState"
+
+func getInfoState(c context.Context) *infoState {
+	if is, ok := c.Value(&infoStateKey).(*infoState); ok {
+		return is
+	}
+	panic("no info state in Context")
+}
+
+func (ci *infoState) use(c context.Context) context.Context {
+	return context.WithValue(c, &infoStateKey, ci)
+}
+
+func (ci *infoState) derive(mutate func(*infoState)) *infoState {
+	dci := *ci
+	mutate(&dci)
+	return &dci
+}
+
+type infoService struct {
+	*infoState
+
+	ic context.Context
+}
+
+func useInfo(c context.Context) context.Context {
+	var baseInfoState infoState
+	c = baseInfoState.use(c)
+
+	return infoS.SetFactory(c, func(ic context.Context) infoS.RawInterface {
+		return &infoService{
+			infoState: getInfoState(ic),
+			ic:        ic,
+		}
+	})
+}
+
+func (i *infoService) AppID() string                { panic(errNotImplemented) }
+func (i *infoService) FullyQualifiedAppID() string  { return "" }
+func (i *infoService) GetNamespace() (string, bool) { return i.namespace, (i.namespace != "") }
+
+func (i *infoService) Datacenter() string             { panic(errNotImplemented) }
+func (i *infoService) DefaultVersionHostname() string { panic(errNotImplemented) }
+func (i *infoService) InstanceID() string             { panic(errNotImplemented) }
+func (i *infoService) IsDevAppServer() bool           { panic(errNotImplemented) }
+func (i *infoService) IsOverQuota(err error) bool     { panic(errNotImplemented) }
+func (i *infoService) IsTimeoutError(err error) bool  { panic(errNotImplemented) }
+func (i *infoService) ModuleHostname(module, version, instance string) (string, error) {
+	return "", errNotImplemented
+}
+func (i *infoService) ModuleName() string              { panic(errNotImplemented) }
+func (i *infoService) RequestID() string               { panic(errNotImplemented) }
+func (i *infoService) ServerSoftware() string          { panic(errNotImplemented) }
+func (i *infoService) ServiceAccount() (string, error) { return "", errNotImplemented }
+func (i *infoService) VersionID() string               { panic(errNotImplemented) }
+
+func (i *infoService) Namespace(namespace string) (context.Context, error) {
+	return i.MustNamespace(namespace), nil
+}
+
+func (i *infoService) MustNamespace(namespace string) context.Context {
+	return i.derive(func(ci *infoState) {
+		ci.namespace = namespace
+	}).use(i.ic)
+}
+
+func (i *infoService) AccessToken(scopes ...string) (token string, expiry time.Time, err error) {
+	return "", time.Time{}, errNotImplemented
+}
+
+func (i *infoService) PublicCertificates() ([]infoS.Certificate, error) {
+	return nil, errNotImplemented
+}
+
+func (i *infoService) SignBytes(bytes []byte) (keyName string, signature []byte, err error) {
+	return "", nil, errNotImplemented
+}
+
+func (i *infoService) Testable() infoS.Testable { return nil }