/
loader.go
254 lines (214 loc) · 7.78 KB
/
loader.go
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package loader
import (
"errors"
serrors "github.com/go-errors/errors"
"github.com/ompluscator/dynamic-struct"
"go.mongodb.org/mongo-driver/bson"
"reflect"
)
//LoaderNotFoundError while can't found loader for the specified version
var LoaderNotFoundError = errors.New("cannot found loader handlers for src version")
//TransformerNotFoundError while can't found Transformer for specified version path transformation progress
var TransformerNotFoundError = errors.New("cannot found next transformer to the target version")
//TransformerSrcTypeIncorrectError while Transformer trying to cast interface{} src data into desired version struct and failed
var TransformerSrcTypeIncorrectError = errors.New("src type for transformer is incorrect and failed to cast")
//NoVersionTagError while loaded data not contain any valid _version tag
var NoVersionTagError = errors.New("data has no _version field or with invalid 0.0 version")
//VersionCapture a Capture for extract the version info from byte data and carry the corresponding version structure data though the progress
type VersionCapture struct {
Version Version `bson:"_version"`
Data interface{}
}
//AVersionCapture use for prevent MarshalBSON loop
type AVersionCapture VersionCapture
//MarshalBSON where VersionCapture deal with version and inline Data
func (v VersionCapture) MarshalBSON() ([]byte, error) {
if v.GetData() != nil {
versionWrapper := GetVersionWrapperStruct(v.GetData()).New()
reflect.ValueOf(versionWrapper).Elem().FieldByName("Data").Set(reflect.ValueOf(v.GetData()))
reflect.ValueOf(versionWrapper).Elem().FieldByName("Version").Set(reflect.ValueOf(v.GetVersion()))
return bson.Marshal(versionWrapper)
}
return bson.Marshal(AVersionCapture(v))
}
//UnmarshalBSON where VersionCapture deal with version and inline Data
func (v *VersionCapture) UnmarshalBSON(src []byte) error {
if v.GetData() != nil {
versionWrapper := GetVersionWrapperStruct(v.GetData()).New()
if err := bson.Unmarshal(src, versionWrapper); err != nil {
return err
}
reader := dynamicstruct.NewReader(versionWrapper)
v.SetVersion(reader.GetField("Version").Interface().(Version))
v.SetData(reader.GetField("Data").Interface())
}
return bson.Unmarshal(src, (*AVersionCapture)(v))
}
//SetVersion set Version
func (v *VersionCapture) SetVersion(vv Version) {
v.Version = vv
}
//GetVersion get Version
func (v VersionCapture) GetVersion() Version {
return v.Version
}
//SetData set Data
func (v *VersionCapture) SetData(d interface{}) {
v.Data = d
}
//GetData get Data
func (v VersionCapture) GetData() interface{} {
return v.Data
}
//Transformer func that responsible for transform the data between Versions
type Transformer func(VersionWrapper) error
type TargetTransformers map[Version]Transformer
type SrcToTargetTransformers map[Version]TargetTransformers
type SrcToTargetVersions map[Version]Versions
//Loader func that responsible for load data for specified Version
type Loader func([]byte, VersionWrapper) error
type SrcLoaders map[Version]Loader
type Registry struct {
loaders SrcLoaders
transformers SrcToTargetTransformers
versions SrcToTargetVersions
}
func (l *Registry) add(src Version, target Version, loader Transformer) {
targetLoaders, ok := l.transformers[src]
if !ok {
targetLoaders = TargetTransformers{}
l.transformers[src] = targetLoaders
}
targetVersions, ok := l.versions[src]
if !ok {
targetVersions = []Version{}
l.versions[src] = targetVersions
}
targetLoaders[target] = loader
l.versions[src] = append(targetVersions, target)
}
//type SLoaders map[string]Loader
type SLoaders map[string]interface{}
type STransformers map[string]STargetTransformers
type STargetTransformers map[string]Transformer
func (l SLoaders) SrcLoaders() SrcLoaders {
s := SrcLoaders{}
for v, l := range l {
if loader, ok := l.(Loader); ok {
s[NewVersionPanic(v)] = loader
} else {
s[NewVersionPanic(v)] = DefaultLoader(l)
}
}
return s
}
func (t STransformers) SrcToTargetTransformers() SrcToTargetTransformers {
s := SrcToTargetTransformers{}
for src, t := range t {
s[NewVersionPanic(src)] = TargetTransformers{}
for tv, tt := range t {
s[NewVersionPanic(src)][NewVersionPanic(tv)] = tt
}
}
return s
}
var DynamicVersionWrapperStructs = map[reflect.Type]dynamicstruct.DynamicStruct{}
func AddVersionWrapperType(typeVal interface{}) dynamicstruct.DynamicStruct {
wrapper := dynamicstruct.NewStruct().
AddField("Version", Version{}, `bson:"_version"`).
AddField("Data", typeVal, `bson:",inline"`).
Build()
DynamicVersionWrapperStructs[reflect.TypeOf(typeVal)] = wrapper
return wrapper
}
func GetVersionWrapperStruct(typeVal interface{}) dynamicstruct.DynamicStruct {
if wrapper, ok := DynamicVersionWrapperStructs[reflect.TypeOf(typeVal)]; ok {
return wrapper
} else {
return AddVersionWrapperType(typeVal)
}
}
//NewRegistry Registry the Loaders and Transformers for migration
func NewRegistry(loadersL SLoaders, transformersT STransformers) *Registry {
l := &Registry{
SrcLoaders{},
SrcToTargetTransformers{},
SrcToTargetVersions{},
}
loaders := loadersL.SrcLoaders()
transformers := transformersT.SrcToTargetTransformers()
for version, loader := range loaders {
l.loaders[version] = loader
}
for srcVersion, targetTransformers := range transformers {
l.transformers[srcVersion] = targetTransformers
l.versions[srcVersion] = Versions{}
for targetVersion := range targetTransformers {
l.versions[srcVersion] = append(l.versions[srcVersion], targetVersion)
}
}
return l
}
//Transform transformation the src Data Struct to target Version
func (l *Registry) Transform(data VersionWrapper, target Version) error {
if data.GetVersion().Greater(target) {
return serrors.Errorf("Raise error from trying donwngrading version %s to %s for %STransformers,please update your target struct version to lastest:%w", data.GetVersion(), target, data, TransformerNotFoundError)
}
for data.GetVersion() != target {
targetVersions, ok := l.versions[data.GetVersion()]
if !ok {
return serrors.Errorf("Raise error from version %s to %s for %STransformers:%w", data.GetVersion(), target, data, TransformerNotFoundError)
}
targetTransformers, ok := l.transformers[data.GetVersion()]
if !ok {
return serrors.Errorf("Raise error from version %s to %s for %STransformers:%w", data.GetVersion(), target, data, TransformerNotFoundError)
}
var nextVersion Version
if _, ok := targetTransformers[target]; ok {
nextVersion = target
} else {
nextVersion = *targetVersions.Max()
}
if err := targetTransformers[nextVersion](data); err != nil {
return err
}
}
return nil
}
//Load load the bson src bytes into target Version,it will return a Version Container with data
func (l *Registry) Load(src []byte, target Version) (VersionWrapper, error) {
versionCapture := VersionCapture{}
if err := bson.Unmarshal(src, &versionCapture); err != nil {
return nil, err
}
if (VersionCapture{}) == versionCapture {
return nil, serrors.Errorf("Raise error %w", NoVersionTagError)
}
var processingTarget VersionWrapper
for version, loader := range l.loaders {
if version == versionCapture.Version {
processingTarget = &VersionCapture{}
if err := loader(src, processingTarget); err != nil {
return nil, serrors.Errorf("Raise error while trying to load data:%w", err)
}
break
}
}
if processingTarget == nil {
return nil, serrors.Errorf("Raise error from src version %s:%w", versionCapture.Version, LoaderNotFoundError)
}
if err := l.Transform(processingTarget, target); err != nil {
return nil, err
}
return processingTarget, nil
}
func DefaultLoader(typeVal interface{}) Loader {
typ := reflect.TypeOf(typeVal)
return func(src []byte, dst VersionWrapper) error {
dst.SetData(reflect.New(typ).Elem().Interface())
if err := bson.Unmarshal(src, dst); err != nil {
return err
}
return nil
}
}