Refactor keys and queries in datastore service and implementation.

service/datastore/dskey/key.go

-// 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.
-
-// adapted from github.com/golang/appengine/datastore
-
-package dskey
-
-import (
-        "bytes"
-        "encoding/base64"
-        "errors"
-        "strconv"
-        "strings"
-
-        "github.com/golang/protobuf/proto"
-        ds "github.com/luci/gae/service/datastore"
-        pb "github.com/luci/gae/service/datastore/internal/protos/datastore"
-)
-
-// Encode encodes the provided key as a base64-encoded protobuf.
-//
-// This encoding is compatible with the SDK-provided encoding and is agnostic
-// to the underlying implementation of the Key.
-//
-// It's encoded with the urlsafe base64 table.
-func Encode(k ds.Key) string {
-        n := 0
-        for i := k; i != nil; i = i.Parent() {
-                n++
-        }
-        e := make([]*pb.Path_Element, n)
-        for i := k; i != nil; i = i.Parent() {
-                n--
-                kind := i.Kind()
-                e[n] = &pb.Path_Element{
-                        Type: &kind,
-                }
-                // At most one of {Name,Id} should be set.
-                // Neither will be set for incomplete keys.
-                if i.StringID() != "" {
-                        sid := i.StringID()
-                        e[n].Name = &sid
-                } else if i.IntID() != 0 {
-                        iid := i.IntID()
-                        e[n].Id = &iid
-                }
-        }
-        var namespace *string
-        if k.Namespace() != "" {
-                namespace = proto.String(k.Namespace())
-        }
-        r, err := proto.Marshal(&pb.Reference{
-                App:       proto.String(k.AppID()),
-                NameSpace: namespace,
-                Path: &pb.Path{
-                        Element: e,
-                },
-        })
-        if err != nil {
-                panic(err)
-        }
-
-        // trim padding
-        return strings.TrimRight(base64.URLEncoding.EncodeToString(r), "=")
-}
-
-// ToksDecode decodes a base64-encoded protobuf representation of a Key
-// into a tokenized form. This is so that implementations of the gae wrapper
-// can decode to their own implementation of Key.
-//
-// This encoding is compatible with the SDK-provided encoding and is agnostic
-// to the underlying implementation of the Key.
-func ToksDecode(encoded string) (appID, namespace string, toks []ds.KeyTok, err error) {
-        // Re-add padding
-        if m := len(encoded) % 4; m != 0 {
-                encoded += strings.Repeat("=", 4-m)
-        }
-        b, err := base64.URLEncoding.DecodeString(encoded)
-        if err != nil {
-                return
-        }
-
-        r := &pb.Reference{}
-        if err = proto.Unmarshal(b, r); err != nil {
-                return
-        }
-
-        appID = r.GetApp()
-        namespace = r.GetNameSpace()
-        toks = make([]ds.KeyTok, len(r.Path.Element))
-        for i, e := range r.Path.Element {
-                toks[i] = ds.KeyTok{
-                        Kind:     e.GetType(),
-                        IntID:    e.GetId(),
-                        StringID: e.GetName(),
-                }
-        }
-        return
-}
-
-// MarshalJSON returns a MarshalJSON-compatible serialization of a Key.
-func MarshalJSON(k ds.Key) ([]byte, error) {
-        return []byte(`"` + Encode(k) + `"`), nil
-}
-
-// UnmarshalJSON returns the tokenized version of a ds.Key as encoded by
-// MarshalJSON.
-func UnmarshalJSON(buf []byte) (appID, namespace string, toks []ds.KeyTok, err error) {
-        if len(buf) < 2 || buf[0] != '"' || buf[len(buf)-1] != '"' {
-                err = errors.New("datastore: bad JSON key")
-        } else {
-                appID, namespace, toks, err = ToksDecode(string(buf[1 : len(buf)-1]))
-        }
-        return
-}
-
-// Incomplete returns true iff k doesn't have an id yet.
-func Incomplete(k ds.Key) bool {
-        return k != nil && k.StringID() == "" && k.IntID() == 0
-}
-
-// Valid determines if a key is valid, according to a couple rules:
-//   - k is not nil
-//   - every token of k:
-//     - (if !allowSpecial) token's kind doesn't start with '__'
-//     - token's kind and appid are non-blank
-//     - token is not incomplete
-//   - all tokens have the same namespace and appid
-func Valid(k ds.Key, allowSpecial bool, aid, ns string) bool {
-        if k == nil {
-                return false
-        }
-        if aid != k.AppID() || ns != k.Namespace() {
-                return false
-        }
-        for ; k != nil; k = k.Parent() {
-                if !allowSpecial && len(k.Kind()) >= 2 && k.Kind()[:2] == "__" {
-                        return false
-                }
-                if k.Kind() == "" || k.AppID() == "" {
-                        return false
-                }
-                if k.StringID() != "" && k.IntID() != 0 {
-                        return false
-                }
-                if k.Parent() != nil {
-                        if k.Parent().Incomplete() {
-                                return false
-                        }
-                        if k.Parent().AppID() != k.AppID() || k.Parent().Namespace() != k.Namespace() {
-                                return false
-                        }
-                }
-        }
-        return true
-}
-
-// PartialValid returns true iff this key is suitable for use in a Put
-// operation. This is the same as Valid(k, false, ...), but also allowing k to
-// be Incomplete().
-func PartialValid(k ds.Key, aid, ns string) bool {
-        if k.Incomplete() {
-                k = New(k.AppID(), k.Namespace(), k.Kind(), "", 1, k.Parent())
-        }
-        return Valid(k, false, aid, ns)
-}
-
-// Root returns the entity root for the given key.
-func Root(k ds.Key) ds.Key {
-        for k != nil && k.Parent() != nil {
-                k = k.Parent()
-        }
-        return k
-}
-
-// Equal returns true iff the two keys represent identical key values.
-func Equal(a, b ds.Key) (ret bool) {
-        ret = (a.Kind() == b.Kind() &&
-                a.StringID() == b.StringID() &&
-                a.IntID() == b.IntID() &&
-                a.AppID() == b.AppID() &&
-                a.Namespace() == b.Namespace())
-        if !ret {
-                return
-        }
-        ap, bp := a.Parent(), b.Parent()
-        return (ap == nil && bp == nil) || Equal(ap, bp)
-}
-
-func marshalDSKey(b *bytes.Buffer, k ds.Key) {
-        if k.Parent() != nil {
-                marshalDSKey(b, k.Parent())
-        }
-        b.WriteByte('/')
-        b.WriteString(k.Kind())
-        b.WriteByte(',')
-        if k.StringID() != "" {
-                b.WriteString(k.StringID())
-        } else {
-                b.WriteString(strconv.FormatInt(k.IntID(), 10))
-        }
-}
-
-// String returns a human-readable representation of the key, and is the
-// typical implementation of Key.String() (though it isn't guaranteed to be)
-func String(k ds.Key) string {
-        if k == nil {
-                return ""
-        }
-        b := bytes.NewBuffer(make([]byte, 0, 512))
-        marshalDSKey(b, k)
-        return b.String()
-}
-
-// Split splits the key into its constituent parts. Note that if the key is
-// not Valid, this method may not provide a round-trip for k.
-func Split(k ds.Key) (appID, namespace string, toks []ds.KeyTok) {
-        if k == nil {
-                return
-        }
-
-        if sk, ok := k.(*Generic); ok {
-                if sk == nil {
-                        return
-                }
-                return sk.appID, sk.namespace, sk.toks
-        }
-
-        n := 0
-        for i := k; i != nil; i = i.Parent() {
-                n++
-        }
-        toks = make([]ds.KeyTok, n)
-        for i := k; i != nil; i = i.Parent() {
-                n--
-                toks[n].IntID = i.IntID()
-                toks[n].StringID = i.StringID()
-                toks[n].Kind = i.Kind()
-        }
-        appID = k.AppID()
-        namespace = k.Namespace()
-        return
-}