Refactor a bit.

helper/datastore_impl.go

Index: helper/datastore_impl.go
diff --git a/helper/datastore_impl.go b/helper/datastore_impl.go
deleted file mode 100644
index 0f7d4de7d6f5cd786d3e6ee6965c7e650293aa32..0000000000000000000000000000000000000000
--- a/helper/datastore_impl.go
+++ /dev/null
@@ -1,574 +0,0 @@
-// 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.
-
-// HEAVILY adapted from github.com/golang/appengine/datastore
-
-package helper
-
-import (
-	"errors"
-	"fmt"
-	"reflect"
-	"strconv"
-	"strings"
-	"sync"
-	"time"
-	"unicode"
-
-	"github.com/luci/gae"
-)
-
-// Entities with more than this many indexed properties will not be saved.
-const maxIndexedProperties = 20000
-
-var (
-	typeOfDSKey               = reflect.TypeOf((*gae.DSKey)(nil)).Elem()
-	typeOfDSPropertyConverter = reflect.TypeOf((*gae.DSPropertyConverter)(nil)).Elem()
-	typeOfGeoPoint            = reflect.TypeOf(gae.DSGeoPoint{})
-	typeOfTime                = reflect.TypeOf(time.Time{})
-	typeOfString              = reflect.TypeOf("")
-	typeOfInt64               = reflect.TypeOf(int64(0))
-	typeOfBool                = reflect.TypeOf(true)
-
-	valueOfnilDSKey = reflect.Zero(typeOfDSKey)
-)
-
-type structTag struct {
-	name           string
-	idxSetting     gae.IndexSetting
-	isSlice        bool
-	substructCodec *structCodec
-	convert        bool
-	metaVal        interface{}
-	canSet         bool
-}
-
-type structCodec struct {
-	byMeta   map[string]int
-	byName   map[string]int
-	byIndex  []structTag
-	hasSlice bool
-	problem  error
-}
-
-type structPLS struct {
-	o reflect.Value
-	c *structCodec
-}
-
-var _ gae.DSPropertyLoadSaver = (*structPLS)(nil)
-
-// typeMismatchReason returns a string explaining why the property p could not
-// be stored in an entity field of type v.Type().
-func typeMismatchReason(val interface{}, v reflect.Value) string {
-	entityType := reflect.TypeOf(val)
-	return fmt.Sprintf("type mismatch: %s versus %v", entityType, v.Type())
-}
-
-func (p *structPLS) Load(propMap gae.DSPropertyMap) error {
-	if err := p.Problem(); err != nil {
-		return err
-	}
-
-	convFailures := gae.MultiError(nil)
-
-	t := reflect.Type(nil)
-	for name, props := range propMap {
-		multiple := len(props) > 1
-		for i, prop := range props {
-			if reason := loadInner(p.c, p.o, i, name, prop, multiple); reason != "" {
-				if t == nil {
-					t = p.o.Type()
-				}
-				convFailures = append(convFailures, &gae.ErrDSFieldMismatch{
-					StructType: t,
-					FieldName:  name,
-					Reason:     reason,
-				})
-			}
-		}
-	}
-
-	if len(convFailures) > 0 {
-		return convFailures
-	}
-
-	return nil
-}
-
-func loadInner(codec *structCodec, structValue reflect.Value, index int, name string, p gae.DSProperty, requireSlice bool) string {
-	var v reflect.Value
-	// Traverse a struct's struct-typed fields.
-	for {
-		fieldIndex, ok := codec.byName[name]
-		if !ok {
-			return "no such struct field"
-		}
-		v = structValue.Field(fieldIndex)
-
-		st := codec.byIndex[fieldIndex]
-		if st.substructCodec == nil {
-			break
-		}
-
-		if v.Kind() == reflect.Slice {
-			for v.Len() <= index {
-				v.Set(reflect.Append(v, reflect.New(v.Type().Elem()).Elem()))
-			}
-			structValue = v.Index(index)
-			requireSlice = false
-		} else {
-			structValue = v
-		}
-		// Strip the "I." from "I.X".
-		name = name[len(st.name):]
-		codec = st.substructCodec
-	}
-
-	doConversion := func(v reflect.Value) (string, bool) {
-		a := v.Addr()
-		if conv, ok := a.Interface().(gae.DSPropertyConverter); ok {
-			err := conv.FromDSProperty(p)
-			if err != nil {
-				return err.Error(), true
-			}
-			return "", true
-		}
-		return "", false
-	}
-
-	if ret, ok := doConversion(v); ok {
-		return ret
-	}
-
-	var slice reflect.Value
-	if v.Kind() == reflect.Slice && v.Type().Elem().Kind() != reflect.Uint8 {
-		slice = v
-		v = reflect.New(v.Type().Elem()).Elem()
-	} else if requireSlice {
-		return "multiple-valued property requires a slice field type"
-	}
-
-	pVal := p.Value()
-
-	if ret, ok := doConversion(v); ok {
-		if ret != "" {
-			return ret
-		}
-	} else {
-		knd := v.Kind()
-		if v.Type().Implements(typeOfDSKey) {
-			knd = reflect.Interface
-		}
-		switch knd {
-		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-			x, ok := pVal.(int64)
-			if !ok && pVal != nil {
-				return typeMismatchReason(pVal, v)
-			}
-			if v.OverflowInt(x) {
-				return fmt.Sprintf("value %v overflows struct field of type %v", x, v.Type())
-			}
-			v.SetInt(x)
-		case reflect.Bool:
-			x, ok := pVal.(bool)
-			if !ok && pVal != nil {
-				return typeMismatchReason(pVal, v)
-			}
-			v.SetBool(x)
-		case reflect.String:
-			switch x := pVal.(type) {
-			case gae.BSKey:
-				v.SetString(string(x))
-			case string:
-				v.SetString(x)
-			default:
-				if pVal != nil {
-					return typeMismatchReason(pVal, v)
-				}
-			}
-		case reflect.Float32, reflect.Float64:
-			x, ok := pVal.(float64)
-			if !ok && pVal != nil {
-				return typeMismatchReason(pVal, v)
-			}
-			if v.OverflowFloat(x) {
-				return fmt.Sprintf("value %v overflows struct field of type %v", x, v.Type())
-			}
-			v.SetFloat(x)
-		case reflect.Interface:
-			x, ok := pVal.(gae.DSKey)
-			if !ok && pVal != nil {
-				return typeMismatchReason(pVal, v)
-			}
-			if x != nil {
-				v.Set(reflect.ValueOf(x))
-			}
-		case reflect.Struct:
-			switch v.Type() {
-			case typeOfTime:
-				x, ok := pVal.(time.Time)
-				if !ok && pVal != nil {
-					return typeMismatchReason(pVal, v)
-				}
-				v.Set(reflect.ValueOf(x))
-			case typeOfGeoPoint:
-				x, ok := pVal.(gae.DSGeoPoint)
-				if !ok && pVal != nil {
-					return typeMismatchReason(pVal, v)
-				}
-				v.Set(reflect.ValueOf(x))
-			default:
-				panic(fmt.Errorf("helper: impossible: %s", typeMismatchReason(pVal, v)))
-			}
-		case reflect.Slice:
-			switch x := pVal.(type) {
-			case []byte:
-				v.SetBytes(x)
-			case gae.DSByteString:
-				v.SetBytes([]byte(x))
-			default:
-				panic(fmt.Errorf("helper: impossible: %s", typeMismatchReason(pVal, v)))
-			}
-		default:
-			panic(fmt.Errorf("helper: impossible: %s", typeMismatchReason(pVal, v)))
-		}
-	}
-	if slice.IsValid() {
-		slice.Set(reflect.Append(slice, v))
-	}
-	return ""
-}
-
-func (p *structPLS) Save(withMeta bool) (gae.DSPropertyMap, error) {
-	size := len(p.c.byName)
-	if withMeta {
-		size += len(p.c.byMeta)
-	}
-	ret := make(gae.DSPropertyMap, size)
-	if _, err := p.save(ret, "", gae.ShouldIndex); err != nil {
-		return nil, err
-	}
-	if withMeta {
-		for k := range p.c.byMeta {
-			val, err := p.GetMeta(k)
-			if err != nil {
-				return nil, err // TODO(riannucci): should these be ignored?
-			}
-			p := gae.DSProperty{}
-			if err = p.SetValue(val, gae.NoIndex); err != nil {
-				return nil, err
-			}
-			ret["$"+k] = []gae.DSProperty{p}
-		}
-	}
-	return ret, nil
-}
-
-func (p *structPLS) save(propMap gae.DSPropertyMap, prefix string, is gae.IndexSetting) (idxCount int, err error) {
-	if err = p.Problem(); err != nil {
-		return
-	}
-
-	saveProp := func(name string, si gae.IndexSetting, v reflect.Value, st *structTag) (err error) {
-		if st.substructCodec != nil {
-			count, err := (&structPLS{v, st.substructCodec}).save(propMap, name, si)
-			if err == nil {
-				idxCount += count
-				if idxCount > maxIndexedProperties {
-					err = errors.New("gae: too many indexed properties")
-				}
-			}
-			return err
-		}
-
-		prop := gae.DSProperty{}
-		if st.convert {
-			prop, err = v.Addr().Interface().(gae.DSPropertyConverter).ToDSProperty()
-		} else {
-			err = prop.SetValue(v.Interface(), si)
-		}
-		if err != nil {
-			return err
-		}
-		propMap[name] = append(propMap[name], prop)
-		if prop.IndexSetting() == gae.ShouldIndex {
-			idxCount++
-			if idxCount > maxIndexedProperties {
-				return errors.New("gae: too many indexed properties")
-			}
-		}
-		return nil
-	}
-
-	for i, st := range p.c.byIndex {
-		if st.name == "-" {
-			continue
-		}
-		name := st.name
-		if prefix != "" {
-			name = prefix + name
-		}
-		v := p.o.Field(i)
-		is1 := is
-		if st.idxSetting == gae.NoIndex {
-			is1 = gae.NoIndex
-		}
-		if st.isSlice {
-			for j := 0; j < v.Len(); j++ {
-				if err = saveProp(name, is1, v.Index(j), &st); err != nil {
-					return
-				}
-			}
-		} else {
-			if err = saveProp(name, is1, v, &st); err != nil {
-				return
-			}
-		}
-	}
-	return
-}
-
-func (p *structPLS) GetMeta(key string) (interface{}, error) {
-	if err := p.Problem(); err != nil {
-		return nil, err
-	}
-	idx, ok := p.c.byMeta[key]
-	if !ok {
-		return nil, gae.ErrDSMetaFieldUnset
-	}
-	st := p.c.byIndex[idx]
-	val := st.metaVal
-	f := p.o.Field(idx)
-	if st.canSet {
-		if !reflect.DeepEqual(reflect.Zero(f.Type()).Interface(), f.Interface()) {
-			val = f.Interface()
-		}
-	}
-	return val, nil
-}
-
-func (p *structPLS) SetMeta(key string, val interface{}) (err error) {
-	if err = p.Problem(); err != nil {
-		return
-	}
-	idx, ok := p.c.byMeta[key]
-	if !ok {
-		return gae.ErrDSMetaFieldUnset
-	}
-	if !p.c.byIndex[idx].canSet {
-		return fmt.Errorf("gae/helper: cannot set meta %q: unexported field", key)
-	}
-	p.o.Field(idx).Set(reflect.ValueOf(val))
-	return nil
-}
-
-func (p *structPLS) Problem() error { return p.c.problem }
-
-var (
-	// The RWMutex is chosen intentionally, as the majority of access to the
-	// structCodecs map will be in parallel and will be to read an existing codec.
-	// There's no reason to serialize goroutines on every
-	// gae.RawDatastore.{Get,Put}{,Multi} call.
-	structCodecsMutex sync.RWMutex
-	structCodecs      = map[reflect.Type]*structCodec{}
-)
-
-// validPropertyName returns whether name consists of one or more valid Go
-// identifiers joined by ".".
-func validPropertyName(name string) bool {
-	if name == "" {
-		return false
-	}
-	for _, s := range strings.Split(name, ".") {
-		if s == "" {
-			return false
-		}
-		first := true
-		for _, c := range s {
-			if first {
-				first = false
-				if c != '_' && !unicode.IsLetter(c) {
-					return false
-				}
-			} else {
-				if c != '_' && !unicode.IsLetter(c) && !unicode.IsDigit(c) {
-					return false
-				}
-			}
-		}
-	}
-	return true
-}
-
-var (
-	errRecursiveStruct = fmt.Errorf("(internal): struct type is recursively defined")
-)
-
-func getStructCodecLocked(t reflect.Type) (c *structCodec) {
-	if c, ok := structCodecs[t]; ok {
-		return c
-	}
-
-	me := func(fmtStr string, args ...interface{}) error {
-		return fmt.Errorf(fmtStr, args...)
-	}
-
-	c = &structCodec{
-		byIndex: make([]structTag, t.NumField()),
-		byName:  make(map[string]int, t.NumField()),
-		byMeta:  make(map[string]int, t.NumField()),
-		problem: errRecursiveStruct, // we'll clear this later if it's not recursive
-	}
-	defer func() {
-		// If the codec has a problem, free up the indexes
-		if c.problem != nil {
-			c.byIndex = nil
-			c.byName = nil
-			c.byMeta = nil
-		}
-	}()
-	structCodecs[t] = c
-
-	for i := range c.byIndex {
-		st := &c.byIndex[i]
-		f := t.Field(i)
-		name := f.Tag.Get("gae")
-		opts := ""
-		if i := strings.Index(name, ","); i != -1 {
-			name, opts = name[:i], name[i+1:]
-		}
-		st.canSet = f.PkgPath == "" // blank == exported
-		switch {
-		case name == "":
-			if !f.Anonymous {
-				name = f.Name
-			}
-		case name[0] == '$':
-			name = name[1:]
-			if _, ok := c.byMeta[name]; ok {
-				c.problem = me("meta field %q set multiple times", "$"+name)
-				return
-			}
-			c.byMeta[name] = i
-			mv, err := convertMeta(opts, f.Type)
-			if err != nil {
-				c.problem = me("meta field %q has bad type: %s", "$"+name, err)
-				return
-			}
-			st.metaVal = mv
-			fallthrough
-		case name == "-":
-			st.name = "-"
-			continue
-		default:
-			if !validPropertyName(name) {
-				c.problem = me("struct tag has invalid property name: %q", name)
-				return
-			}
-		}
-		if !st.canSet {
-			st.name = "-"
-			continue
-		}
-
-		substructType := reflect.Type(nil)
-		ft := f.Type
-		if reflect.PtrTo(ft).Implements(typeOfDSPropertyConverter) {
-			st.convert = true
-		} else {
-			switch f.Type.Kind() {
-			case reflect.Struct:
-				if ft != typeOfTime && ft != typeOfGeoPoint {
-					substructType = ft
-				}
-			case reflect.Slice:
-				if reflect.PtrTo(ft.Elem()).Implements(typeOfDSPropertyConverter) {
-					st.convert = true
-				} else if ft.Elem().Kind() == reflect.Struct {
-					substructType = ft.Elem()
-				}
-				st.isSlice = ft.Elem().Kind() != reflect.Uint8
-				c.hasSlice = c.hasSlice || st.isSlice
-			case reflect.Interface:
-				if ft != typeOfDSKey {
-					c.problem = me("field %q has non-concrete interface type %s",
-						f.Name, f.Type)
-					return
-				}
-			}
-		}
-
-		if substructType != nil {
-			sub := getStructCodecLocked(substructType)
-			if sub.problem != nil {
-				if sub.problem == errRecursiveStruct {
-					c.problem = me("field %q is recursively defined", f.Name)
-				} else {
-					c.problem = me("field %q has problem: %s", f.Name, sub.problem)
-				}
-				return
-			}
-			st.substructCodec = sub
-			if st.isSlice && sub.hasSlice {
-				c.problem = me(
-					"flattening nested structs leads to a slice of slices: field %q",
-					f.Name)
-				return
-			}
-			c.hasSlice = c.hasSlice || sub.hasSlice
-			if name != "" {
-				name += "."
-			}
-			for relName := range sub.byName {
-				absName := name + relName
-				if _, ok := c.byName[absName]; ok {
-					c.problem = me("struct tag has repeated property name: %q", absName)
-					return
-				}
-				c.byName[absName] = i
-			}
-		} else {
-			if !st.convert { // check the underlying static type of the field
-				t := ft
-				if st.isSlice {
-					t = t.Elem()
-				}
-				v := reflect.New(t).Elem().Interface()
-				v, _ = gae.DSUpconvertUnderlyingType(v, t)
-				if _, err := gae.DSPropertyTypeOf(v, false); err != nil {
-					c.problem = me("field %q has invalid type: %s", name, ft)
-					return
-				}
-			}
-
-			if _, ok := c.byName[name]; ok {
-				c.problem = me("struct tag has repeated property name: %q", name)
-				return
-			}
-			c.byName[name] = i
-		}
-		st.name = name
-		if opts == "noindex" {
-			st.idxSetting = gae.NoIndex
-		}
-	}
-	if c.problem == errRecursiveStruct {
-		c.problem = nil
-	}
-	return
-}
-
-func convertMeta(val string, t reflect.Type) (interface{}, error) {
-	switch t {
-	case typeOfString:
-		return val, nil
-	case typeOfInt64:
-		if val == "" {
-			return int64(0), nil
-		}
-		return strconv.ParseInt(val, 10, 64)
-	}
-	return nil, fmt.Errorf("helper: meta field with bad type/value %s/%s", t, val)
-}