text: // Copyright 2018 The Go 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 impl
  
  import (
  	"fmt"
  	"reflect"
  	"strings"
  	"sync"
  
  	"google.golang.org/protobuf/internal/descopts"
  	ptag "google.golang.org/protobuf/internal/encoding/tag"
  	"google.golang.org/protobuf/internal/errors"
  	"google.golang.org/protobuf/internal/filedesc"
  	"google.golang.org/protobuf/internal/strs"
  	"google.golang.org/protobuf/reflect/protoreflect"
  	pref "google.golang.org/protobuf/reflect/protoreflect"
  	"google.golang.org/protobuf/runtime/protoiface"
  	piface "google.golang.org/protobuf/runtime/protoiface"
  )
  
  // legacyWrapMessage wraps v as a protoreflect.Message,
  // where v must be a *struct kind and not implement the v2 API already.
  func legacyWrapMessage(v reflect.Value) pref.Message {
  	typ := v.Type()
  	if typ.Kind() != reflect.Ptr || typ.Elem().Kind() != reflect.Struct {
  		return aberrantMessage{v: v}
  	}
  	mt := legacyLoadMessageInfo(typ, "")
  	return mt.MessageOf(v.Interface())
  }
  
  var legacyMessageTypeCache sync.Map // map[reflect.Type]*MessageInfo
  
  // legacyLoadMessageInfo dynamically loads a *MessageInfo for t,
  // where t must be a *struct kind and not implement the v2 API already.
  // The provided name is used if it cannot be determined from the message.
  func legacyLoadMessageInfo(t reflect.Type, name pref.FullName) *MessageInfo {
  	// Fast-path: check if a MessageInfo is cached for this concrete type.
  	if mt, ok := legacyMessageTypeCache.Load(t); ok {
  		return mt.(*MessageInfo)
  	}
  
  	// Slow-path: derive message descriptor and initialize MessageInfo.
  	mi := &MessageInfo{
  		Desc:          legacyLoadMessageDesc(t, name),
  		GoReflectType: t,
  	}
  
  	v := reflect.Zero(t).Interface()
  	if _, ok := v.(legacyMarshaler); ok {
  		mi.methods.Marshal = legacyMarshal
  
  		// We have no way to tell whether the type's Marshal method
  		// supports deterministic serialization or not, but this
  		// preserves the v1 implementation's behavior of always
  		// calling Marshal methods when present.
  		mi.methods.Flags |= piface.SupportMarshalDeterministic
  	}
  	if _, ok := v.(legacyUnmarshaler); ok {
  		mi.methods.Unmarshal = legacyUnmarshal
  	}
  	if _, ok := v.(legacyMerger); ok {
  		mi.methods.Merge = legacyMerge
  	}
  
  	if mi, ok := legacyMessageTypeCache.LoadOrStore(t, mi); ok {
  		return mi.(*MessageInfo)
  	}
  	return mi
  }
  
  var legacyMessageDescCache sync.Map // map[reflect.Type]protoreflect.MessageDescriptor
  
  // LegacyLoadMessageDesc returns an MessageDescriptor derived from the Go type,
  // which must be a *struct kind and not implement the v2 API already.
  //
  // This is exported for testing purposes.
  func LegacyLoadMessageDesc(t reflect.Type) pref.MessageDescriptor {
  	return legacyLoadMessageDesc(t, "")
  }
  func legacyLoadMessageDesc(t reflect.Type, name pref.FullName) pref.MessageDescriptor {
  	// Fast-path: check if a MessageDescriptor is cached for this concrete type.
  	if mi, ok := legacyMessageDescCache.Load(t); ok {
  		return mi.(pref.MessageDescriptor)
  	}
  
  	// Slow-path: initialize MessageDescriptor from the raw descriptor.
  	mv := reflect.Zero(t).Interface()
  	if _, ok := mv.(pref.ProtoMessage); ok {
  		panic(fmt.Sprintf("%v already implements proto.Message", t))
  	}
  	mdV1, ok := mv.(messageV1)
  	if !ok {
  		return aberrantLoadMessageDesc(t, name)
  	}
  
  	// If this is a dynamic message type where there isn't a 1-1 mapping between
  	// Go and protobuf types, calling the Descriptor method on the zero value of
  	// the message type isn't likely to work. If it panics, swallow the panic and
  	// continue as if the Descriptor method wasn't present.
  	b, idxs := func() ([]byte, []int) {
  		defer func() {
  			recover()
  		}()
  		return mdV1.Descriptor()
  	}()
  	if b == nil {
  		return aberrantLoadMessageDesc(t, name)
  	}
  
  	// If the Go type has no fields, then this might be a proto3 empty message
  	// from before the size cache was added. If there are any fields, check to
  	// see that at least one of them looks like something we generated.
  	if nfield := t.Elem().NumField(); nfield > 0 {
  		hasProtoField := false
  		for i := 0; i < nfield; i++ {
  			f := t.Elem().Field(i)
  			if f.Tag.Get("protobuf") != "" || f.Tag.Get("protobuf_oneof") != "" || strings.HasPrefix(f.Name, "XXX_") {
  				hasProtoField = true
  				break
  			}
  		}
  		if !hasProtoField {
  			return aberrantLoadMessageDesc(t, name)
  		}
  	}
  
  	md := legacyLoadFileDesc(b).Messages().Get(idxs[0])
  	for _, i := range idxs[1:] {
  		md = md.Messages().Get(i)
  	}
  	if name != "" && md.FullName() != name {
  		panic(fmt.Sprintf("mismatching message name: got %v, want %v", md.FullName(), name))
  	}
  	if md, ok := legacyMessageDescCache.LoadOrStore(t, md); ok {
  		return md.(protoreflect.MessageDescriptor)
  	}
  	return md
  }
  
  var (
  	aberrantMessageDescLock  sync.Mutex
  	aberrantMessageDescCache map[reflect.Type]protoreflect.MessageDescriptor
  )
  
  // aberrantLoadMessageDesc returns an MessageDescriptor derived from the Go type,
  // which must not implement protoreflect.ProtoMessage or messageV1.
  //
  // This is a best-effort derivation of the message descriptor using the protobuf
  // tags on the struct fields.
  func aberrantLoadMessageDesc(t reflect.Type, name pref.FullName) pref.MessageDescriptor {
  	aberrantMessageDescLock.Lock()
  	defer aberrantMessageDescLock.Unlock()
  	if aberrantMessageDescCache == nil {
  		aberrantMessageDescCache = make(map[reflect.Type]protoreflect.MessageDescriptor)
  	}
  	return aberrantLoadMessageDescReentrant(t, name)
  }
  func aberrantLoadMessageDescReentrant(t reflect.Type, name pref.FullName) pref.MessageDescriptor {
  	// Fast-path: check if an MessageDescriptor is cached for this concrete type.
  	if md, ok := aberrantMessageDescCache[t]; ok {
  		return md
  	}
  
  	// Slow-path: construct a descriptor from the Go struct type (best-effort).
  	// Cache the MessageDescriptor early on so that we can resolve internal
  	// cyclic references.
  	md := &filedesc.Message{L2: new(filedesc.MessageL2)}
  	md.L0.FullName = aberrantDeriveMessageName(t, name)
  	md.L0.ParentFile = filedesc.SurrogateProto2
  	aberrantMessageDescCache[t] = md
  
  	if t.Kind() != reflect.Ptr || t.Elem().Kind() != reflect.Struct {
  		return md
  	}
  
  	// Try to determine if the message is using proto3 by checking scalars.
  	for i := 0; i < t.Elem().NumField(); i++ {
  		f := t.Elem().Field(i)
  		if tag := f.Tag.Get("protobuf"); tag != "" {
  			switch f.Type.Kind() {
  			case reflect.Bool, reflect.Int32, reflect.Int64, reflect.Uint32, reflect.Uint64, reflect.Float32, reflect.Float64, reflect.String:
  				md.L0.ParentFile = filedesc.SurrogateProto3
  			}
  			for _, s := range strings.Split(tag, ",") {
  				if s == "proto3" {
  					md.L0.ParentFile = filedesc.SurrogateProto3
  				}
  			}
  		}
  	}
  
  	// Obtain a list of oneof wrapper types.
  	var oneofWrappers []reflect.Type
  	for _, method := range []string{"XXX_OneofFuncs", "XXX_OneofWrappers"} {
  		if fn, ok := t.MethodByName(method); ok {
  			for _, v := range fn.Func.Call([]reflect.Value{reflect.Zero(fn.Type.In(0))}) {
  				if vs, ok := v.Interface().([]interface{}); ok {
  					for _, v := range vs {
  						oneofWrappers = append(oneofWrappers, reflect.TypeOf(v))
  					}
  				}
  			}
  		}
  	}
  
  	// Obtain a list of the extension ranges.
  	if fn, ok := t.MethodByName("ExtensionRangeArray"); ok {
  		vs := fn.Func.Call([]reflect.Value{reflect.Zero(fn.Type.In(0))})[0]
  		for i := 0; i < vs.Len(); i++ {
  			v := vs.Index(i)
  			md.L2.ExtensionRanges.List = append(md.L2.ExtensionRanges.List, [2]pref.FieldNumber{
  				pref.FieldNumber(v.FieldByName("Start").Int()),
  				pref.FieldNumber(v.FieldByName("End").Int() + 1),
  			})
  			md.L2.ExtensionRangeOptions = append(md.L2.ExtensionRangeOptions, nil)
  		}
  	}
  
  	// Derive the message fields by inspecting the struct fields.
  	for i := 0; i < t.Elem().NumField(); i++ {
  		f := t.Elem().Field(i)
  		if tag := f.Tag.Get("protobuf"); tag != "" {
  			tagKey := f.Tag.Get("protobuf_key")
  			tagVal := f.Tag.Get("protobuf_val")
  			aberrantAppendField(md, f.Type, tag, tagKey, tagVal)
  		}
  		if tag := f.Tag.Get("protobuf_oneof"); tag != "" {
  			n := len(md.L2.Oneofs.List)
  			md.L2.Oneofs.List = append(md.L2.Oneofs.List, filedesc.Oneof{})
  			od := &md.L2.Oneofs.List[n]
  			od.L0.FullName = md.FullName().Append(pref.Name(tag))
  			od.L0.ParentFile = md.L0.ParentFile
  			od.L0.Parent = md
  			od.L0.Index = n
  
  			for _, t := range oneofWrappers {
  				if t.Implements(f.Type) {
  					f := t.Elem().Field(0)
  					if tag := f.Tag.Get("protobuf"); tag != "" {
  						aberrantAppendField(md, f.Type, tag, "", "")
  						fd := &md.L2.Fields.List[len(md.L2.Fields.List)-1]
  						fd.L1.ContainingOneof = od
  						od.L1.Fields.List = append(od.L1.Fields.List, fd)
  					}
  				}
  			}
  		}
  	}
  
  	return md
  }
  
  func aberrantDeriveMessageName(t reflect.Type, name pref.FullName) pref.FullName {
  	if name.IsValid() {
  		return name
  	}
  	func() {
  		defer func() { recover() }() // swallow possible nil panics
  		if m, ok := reflect.Zero(t).Interface().(interface{ XXX_MessageName() string }); ok {
  			name = pref.FullName(m.XXX_MessageName())
  		}
  	}()
  	if name.IsValid() {
  		return name
  	}
  	if t.Kind() == reflect.Ptr {
  		t = t.Elem()
  	}
  	return AberrantDeriveFullName(t)
  }
  
  func aberrantAppendField(md *filedesc.Message, goType reflect.Type, tag, tagKey, tagVal string) {
  	t := goType
  	isOptional := t.Kind() == reflect.Ptr && t.Elem().Kind() != reflect.Struct
  	isRepeated := t.Kind() == reflect.Slice && t.Elem().Kind() != reflect.Uint8
  	if isOptional || isRepeated {
  		t = t.Elem()
  	}
  	fd := ptag.Unmarshal(tag, t, placeholderEnumValues{}).(*filedesc.Field)
  
  	// Append field descriptor to the message.
  	n := len(md.L2.Fields.List)
  	md.L2.Fields.List = append(md.L2.Fields.List, *fd)
  	fd = &md.L2.Fields.List[n]
  	fd.L0.FullName = md.FullName().Append(fd.Name())
  	fd.L0.ParentFile = md.L0.ParentFile
  	fd.L0.Parent = md
  	fd.L0.Index = n
  
  	if fd.L1.IsWeak || fd.L1.HasPacked {
  		fd.L1.Options = func() pref.ProtoMessage {
  			opts := descopts.Field.ProtoReflect().New()
  			if fd.L1.IsWeak {
  				opts.Set(opts.Descriptor().Fields().ByName("weak"), protoreflect.ValueOfBool(true))
  			}
  			if fd.L1.HasPacked {
  				opts.Set(opts.Descriptor().Fields().ByName("packed"), protoreflect.ValueOfBool(fd.L1.IsPacked))
  			}
  			return opts.Interface()
  		}
  	}
  
  	// Populate Enum and Message.
  	if fd.Enum() == nil && fd.Kind() == pref.EnumKind {
  		switch v := reflect.Zero(t).Interface().(type) {
  		case pref.Enum:
  			fd.L1.Enum = v.Descriptor()
  		default:
  			fd.L1.Enum = LegacyLoadEnumDesc(t)
  		}
  	}
  	if fd.Message() == nil && (fd.Kind() == pref.MessageKind || fd.Kind() == pref.GroupKind) {
  		switch v := reflect.Zero(t).Interface().(type) {
  		case pref.ProtoMessage:
  			fd.L1.Message = v.ProtoReflect().Descriptor()
  		case messageV1:
  			fd.L1.Message = LegacyLoadMessageDesc(t)
  		default:
  			if t.Kind() == reflect.Map {
  				n := len(md.L1.Messages.List)
  				md.L1.Messages.List = append(md.L1.Messages.List, filedesc.Message{L2: new(filedesc.MessageL2)})
  				md2 := &md.L1.Messages.List[n]
  				md2.L0.FullName = md.FullName().Append(pref.Name(strs.MapEntryName(string(fd.Name()))))
  				md2.L0.ParentFile = md.L0.ParentFile
  				md2.L0.Parent = md
  				md2.L0.Index = n
  
  				md2.L1.IsMapEntry = true
  				md2.L2.Options = func() pref.ProtoMessage {
  					opts := descopts.Message.ProtoReflect().New()
  					opts.Set(opts.Descriptor().Fields().ByName("map_entry"), protoreflect.ValueOfBool(true))
  					return opts.Interface()
  				}
  
  				aberrantAppendField(md2, t.Key(), tagKey, "", "")
  				aberrantAppendField(md2, t.Elem(), tagVal, "", "")
  
  				fd.L1.Message = md2
  				break
  			}
  			fd.L1.Message = aberrantLoadMessageDescReentrant(t, "")
  		}
  	}
  }
  
  type placeholderEnumValues struct {
  	protoreflect.EnumValueDescriptors
  }
  
  func (placeholderEnumValues) ByNumber(n pref.EnumNumber) pref.EnumValueDescriptor {
  	return filedesc.PlaceholderEnumValue(pref.FullName(fmt.Sprintf("UNKNOWN_%d", n)))
  }
  
  // legacyMarshaler is the proto.Marshaler interface superseded by protoiface.Methoder.
  type legacyMarshaler interface {
  	Marshal() ([]byte, error)
  }
  
  // legacyUnmarshaler is the proto.Unmarshaler interface superseded by protoiface.Methoder.
  type legacyUnmarshaler interface {
  	Unmarshal([]byte) error
  }
  
  // legacyMerger is the proto.Merger interface superseded by protoiface.Methoder.
  type legacyMerger interface {
  	Merge(protoiface.MessageV1)
  }
  
  var legacyProtoMethods = &piface.Methods{
  	Marshal:   legacyMarshal,
  	Unmarshal: legacyUnmarshal,
  	Merge:     legacyMerge,
  
  	// We have no way to tell whether the type's Marshal method
  	// supports deterministic serialization or not, but this
  	// preserves the v1 implementation's behavior of always
  	// calling Marshal methods when present.
  	Flags: piface.SupportMarshalDeterministic,
  }
  
  func legacyMarshal(in piface.MarshalInput) (piface.MarshalOutput, error) {
  	v := in.Message.(unwrapper).protoUnwrap()
  	marshaler, ok := v.(legacyMarshaler)
  	if !ok {
  		return piface.MarshalOutput{}, errors.New("%T does not implement Marshal", v)
  	}
  	out, err := marshaler.Marshal()
  	if in.Buf != nil {
  		out = append(in.Buf, out...)
  	}
  	return piface.MarshalOutput{
  		Buf: out,
  	}, err
  }
  
  func legacyUnmarshal(in piface.UnmarshalInput) (piface.UnmarshalOutput, error) {
  	v := in.Message.(unwrapper).protoUnwrap()
  	unmarshaler, ok := v.(legacyUnmarshaler)
  	if !ok {
  		return piface.UnmarshalOutput{}, errors.New("%T does not implement Marshal", v)
  	}
  	return piface.UnmarshalOutput{}, unmarshaler.Unmarshal(in.Buf)
  }
  
  func legacyMerge(in piface.MergeInput) piface.MergeOutput {
  	dstv := in.Destination.(unwrapper).protoUnwrap()
  	merger, ok := dstv.(legacyMerger)
  	if !ok {
  		return piface.MergeOutput{}
  	}
  	merger.Merge(Export{}.ProtoMessageV1Of(in.Source))
  	return piface.MergeOutput{Flags: piface.MergeComplete}
  }
  
  // aberrantMessageType implements MessageType for all types other than pointer-to-struct.
  type aberrantMessageType struct {
  	t reflect.Type
  }
  
  func (mt aberrantMessageType) New() pref.Message {
  	return aberrantMessage{reflect.Zero(mt.t)}
  }
  func (mt aberrantMessageType) Zero() pref.Message {
  	return aberrantMessage{reflect.Zero(mt.t)}
  }
  func (mt aberrantMessageType) GoType() reflect.Type {
  	return mt.t
  }
  func (mt aberrantMessageType) Descriptor() pref.MessageDescriptor {
  	return LegacyLoadMessageDesc(mt.t)
  }
  
  // aberrantMessage implements Message for all types other than pointer-to-struct.
  //
  // When the underlying type implements legacyMarshaler or legacyUnmarshaler,
  // the aberrant Message can be marshaled or unmarshaled. Otherwise, there is
  // not much that can be done with values of this type.
  type aberrantMessage struct {
  	v reflect.Value
  }
  
  func (m aberrantMessage) ProtoReflect() pref.Message {
  	return m
  }
  
  func (m aberrantMessage) Descriptor() pref.MessageDescriptor {
  	return LegacyLoadMessageDesc(m.v.Type())
  }
  func (m aberrantMessage) Type() pref.MessageType {
  	return aberrantMessageType{m.v.Type()}
  }
  func (m aberrantMessage) New() pref.Message {
  	return aberrantMessage{reflect.Zero(m.v.Type())}
  }
  func (m aberrantMessage) Interface() pref.ProtoMessage {
  	return m
  }
  func (m aberrantMessage) Range(f func(pref.FieldDescriptor, pref.Value) bool) {
  }
  func (m aberrantMessage) Has(pref.FieldDescriptor) bool {
  	panic("invalid field descriptor")
  }
  func (m aberrantMessage) Clear(pref.FieldDescriptor) {
  	panic("invalid field descriptor")
  }
  func (m aberrantMessage) Get(pref.FieldDescriptor) pref.Value {
  	panic("invalid field descriptor")
  }
  func (m aberrantMessage) Set(pref.FieldDescriptor, pref.Value) {
  	panic("invalid field descriptor")
  }
  func (m aberrantMessage) Mutable(pref.FieldDescriptor) pref.Value {
  	panic("invalid field descriptor")
  }
  func (m aberrantMessage) NewField(pref.FieldDescriptor) pref.Value {
  	panic("invalid field descriptor")
  }
  func (m aberrantMessage) WhichOneof(pref.OneofDescriptor) pref.FieldDescriptor {
  	panic("invalid oneof descriptor")
  }
  func (m aberrantMessage) GetUnknown() pref.RawFields {
  	return nil
  }
  func (m aberrantMessage) SetUnknown(pref.RawFields) {
  	// SetUnknown discards its input on messages which don't support unknown field storage.
  }
  func (m aberrantMessage) IsValid() bool {
  	// An invalid message is a read-only, empty message. Since we don't know anything
  	// about the alleged contents of this message, we can't say with confidence that
  	// it is invalid in this sense. Therefore, report it as valid.
  	return true
  }
  func (m aberrantMessage) ProtoMethods() *piface.Methods {
  	return legacyProtoMethods
  }
  func (m aberrantMessage) protoUnwrap() interface{} {
  	return m.v.Interface()
  }
  