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

go/src/infra/gae/libs/gae/raw_datastore.go

Index: go/src/infra/gae/libs/gae/raw_datastore.go
diff --git a/go/src/infra/gae/libs/gae/raw_datastore.go b/go/src/infra/gae/libs/gae/raw_datastore.go
new file mode 100644
index 0000000000000000000000000000000000000000..100b7d9471c850bbb1c7fff79286fdd0c41ce25d
--- /dev/null
+++ b/go/src/infra/gae/libs/gae/raw_datastore.go
@@ -0,0 +1,116 @@
+// 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 gae
+
+import (
+	"fmt"
+
+	"golang.org/x/net/context"
+)
+
+/// Kinds + Keys
+
+// DSKey is the equivalent of *datastore.Key from the original SDK, except that
+// it can have multiple implementations. See helper.DSKey* methods for missing
+// methods like DSKeyIncomplete (and some new ones like DSKeyValid).
+type DSKey interface {
+	Kind() string
+	StringID() string
+	IntID() int64
+	Parent() DSKey
+	AppID() string
+	Namespace() string
+
+	String() string
+}
+
+// DSKeyTok is a single token from a multi-part DSKey.
+type DSKeyTok struct {
+	Kind     string
+	IntID    int64
+	StringID string
+}
+
+// DSCursor wraps datastore.Cursor.
+type DSCursor interface {
+	fmt.Stringer
+}
+
+// DSIterator wraps datastore.Iterator.
+type DSIterator interface {
+	Cursor() (DSCursor, error)
+	Next(dst interface{}) (DSKey, error)
+}
+
+// DSQuery wraps datastore.Query.
+type DSQuery interface {
+	Ancestor(ancestor DSKey) DSQuery
+	Distinct() DSQuery
+	End(c DSCursor) DSQuery
+	EventualConsistency() DSQuery
+	Filter(filterStr string, value interface{}) DSQuery
+	KeysOnly() DSQuery
+	Limit(limit int) DSQuery
+	Offset(offset int) DSQuery
+	Order(fieldName string) DSQuery
+	Project(fieldNames ...string) DSQuery
+	Start(c DSCursor) DSQuery
+}
+
+// CommonDatastore is the interface for the methods which are common between
+// Datastore and RawDatastore.
+type CommonDatastore interface {
+	NewKey(kind, stringID string, intID int64, parent DSKey) DSKey
+	DecodeKey(encoded string) (DSKey, error)
+
+	NewQuery(kind string) DSQuery
+	Run(q DSQuery) DSIterator
+	GetAll(q DSQuery, dst interface{}) ([]DSKey, error)
+	Count(q DSQuery) (int, error)
+
+	RunInTransaction(f func(c context.Context) error, opts *DSTransactionOptions) error
+}
+
+// RawDatastore implements the datastore functionality as described by
+// the raw appengine documentation. No key inference occurs, nor does any
+// caching. See Datastore for a nicer interface.
+type RawDatastore interface {
+	CommonDatastore
+
+	Put(key DSKey, src interface{}) (DSKey, error)
+	Get(key DSKey, dst interface{}) error
+	Delete(key DSKey) error
+
+	// These allow you to read and write a multiple datastore objects in
+	// a non-atomic batch.
+	DeleteMulti(keys []DSKey) error
+	GetMulti(keys []DSKey, dst interface{}) error
+	PutMulti(keys []DSKey, src interface{}) ([]DSKey, error)
+}
+
+// RDSFactory is the function signature for factory methods compatible with
+// SetRDSFactory.
+type RDSFactory func(context.Context) RawDatastore
+
+// GetRDS gets the RawDatastore implementation from context.
+func GetRDS(c context.Context) RawDatastore {
+	if f, ok := c.Value(rawDatastoreKey).(RDSFactory); ok && f != nil {
+		return f(c)
+	}
+	return nil
+}
+
+// SetRDSFactory sets the function to produce Datastore instances, as returned by
+// the GetRDS method.
+func SetRDSFactory(c context.Context, rdsf RDSFactory) context.Context {
+	return context.WithValue(c, rawDatastoreKey, rdsf)
+}
+
+// SetRDS sets the current Datastore object in the context. Useful for testing
+// with a quick mock. This is just a shorthand SetDSFactory invocation to set
+// a factory which always returns the same object.
+func SetRDS(c context.Context, rds RawDatastore) context.Context {
+	return SetRDSFactory(c, func(context.Context) RawDatastore { return rds })
+}