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package protoregistry
import (
"errors"
"fmt"
"reflect"
"regexp"
"strconv"
"gitlab.com/gitlab-org/gitaly/v16/proto/go/gitalypb"
"google.golang.org/protobuf/proto"
)
const (
protobufTag = "protobuf"
protobufOneOfTag = "protobuf_oneof"
)
// ErrTargetRepoMissing indicates that the target repo is missing or not set
var ErrTargetRepoMissing = errors.New("empty Repository")
func reflectFindRepoTarget(pbMsg proto.Message, targetOID []int) (*gitalypb.Repository, error) {
msgV, e := reflectFindOID(pbMsg, targetOID)
if e != nil {
if e == ErrProtoFieldEmpty {
return nil, ErrTargetRepoMissing
}
return nil, e
}
targetRepo, ok := msgV.Interface().(*gitalypb.Repository)
if !ok {
return nil, fmt.Errorf("repo target OID %v points to non-Repo type %+v", targetOID, msgV.Interface())
}
return targetRepo, nil
}
func reflectFindStorage(pbMsg proto.Message, targetOID []int) (string, error) {
msgV, e := reflectFindOID(pbMsg, targetOID)
if e != nil {
return "", e
}
targetRepo, ok := msgV.Interface().(string)
if !ok {
return "", fmt.Errorf("repo target OID %v points to non-string type %+v", targetOID, msgV.Interface())
}
return targetRepo, nil
}
func reflectSetStorage(pbMsg proto.Message, targetOID []int, storage string) error {
msgV, err := reflectFindOID(pbMsg, targetOID)
if err != nil {
return err
}
msgV.Set(reflect.ValueOf(storage))
return nil
}
// ErrProtoFieldEmpty indicates the protobuf field is empty
var ErrProtoFieldEmpty = errors.New("proto field is empty")
// reflectFindOID finds the target repository by using the OID to
// navigate the struct tags
// Warning: this reflection filled function is full of forbidden dark elf magic
func reflectFindOID(pbMsg proto.Message, targetOID []int) (reflect.Value, error) {
msgV := reflect.ValueOf(pbMsg)
for _, fieldNo := range targetOID {
var err error
msgV, err = findProtoField(msgV, fieldNo)
if err != nil {
return reflect.Value{}, fmt.Errorf(
"unable to descend OID %+v into message %s: %v",
targetOID, proto.MessageName(pbMsg), err,
)
}
}
return msgV, nil
}
// matches a tag string like "bytes,1,opt,name=repository,proto3"
var protobufTagRegex = regexp.MustCompile(`^(.*?),(\d+),(.*?),name=(.*?),proto3(\,oneof)?$`)
const (
protobufTagRegexGroups = 6
protobufTagRegexFieldGroup = 2
)
func findProtoField(msgV reflect.Value, protoField int) (reflect.Value, error) {
if msgV.IsZero() {
return reflect.Value{}, ErrProtoFieldEmpty
}
msgV = reflect.Indirect(msgV)
for i := 0; i < msgV.NumField(); i++ {
field := msgV.Type().Field(i)
ok, err := tryNumberedField(field, protoField)
if err != nil {
return reflect.Value{}, err
}
if ok {
return msgV.FieldByName(field.Name), nil
}
oneofField, ok := tryOneOfField(msgV, field, protoField)
if !ok {
continue
}
return oneofField, nil
}
err := fmt.Errorf(
"unable to find protobuf field %d in message %s",
protoField, msgV.Type().Name(),
)
return reflect.Value{}, err
}
func tryNumberedField(field reflect.StructField, protoField int) (bool, error) {
tag := field.Tag.Get(protobufTag)
matches := protobufTagRegex.FindStringSubmatch(tag)
if len(matches) == protobufTagRegexGroups {
fieldStr := matches[protobufTagRegexFieldGroup]
if fieldStr == strconv.Itoa(protoField) {
return true, nil
}
}
return false, nil
}
func tryOneOfField(msgV reflect.Value, field reflect.StructField, protoField int) (reflect.Value, bool) {
if msgV.IsZero() {
return reflect.Value{}, false
}
oneOfTag := field.Tag.Get(protobufOneOfTag)
if oneOfTag == "" {
return reflect.Value{}, false // empty tag means this is not a oneOf field
}
// try all of the oneOf fields until a match is found
msgV = msgV.FieldByName(field.Name).Elem().Elem()
for i := 0; i < msgV.NumField(); i++ {
field = msgV.Type().Field(i)
ok, err := tryNumberedField(field, protoField)
if err != nil {
return reflect.Value{}, false
}
if ok {
return msgV.FieldByName(field.Name), true
}
}
return reflect.Value{}, false
}
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