move lib/go/gremlin to ent/dialect (#1192)

Summary:
Pull Request resolved: https://github.com/facebookexternal/fbc/pull/1192

Pull Request resolved: https://github.com/facebookincubator/ent/pull/11

Reviewed By: alexsn

Differential Revision: D16377224

fbshipit-source-id: 07ca7436eb9b64fbe2299568560b91466b2417ba

dialect/gremlin/encoding/graphson/encode.go

@@ -0,0 +1,94 @@
+package graphson
+
+import (
+	"io"
+	"reflect"
+
+	"github.com/json-iterator/go"
+	"github.com/modern-go/reflect2"
+)
+
+type encodeExtension struct {
+	jsoniter.DummyExtension
+}
+
+// Marshal returns the graphson encoding of v.
+func Marshal(v interface{}) ([]byte, error) {
+	return config.Marshal(v)
+}
+
+// MarshalToString returns the graphson encoding of v as string.
+func MarshalToString(v interface{}) (string, error) {
+	return config.MarshalToString(v)
+}
+
+// Encoder defines a graphson encoder.
+type Encoder interface {
+	Encode(interface{}) error
+}
+
+// NewEncoder create a graphson encoder.
+func NewEncoder(w io.Writer) Encoder {
+	return config.NewEncoder(w)
+}
+
+// Marshaler is the interface implemented by types that
+// can marshal themselves as graphson.
+type Marshaler interface {
+	MarshalGraphson() ([]byte, error)
+}
+
+// UpdateStructDescriptor decorates struct field encoders for graphson tags.
+func (ext encodeExtension) UpdateStructDescriptor(desc *jsoniter.StructDescriptor) {
+	for _, binding := range desc.Fields {
+		if tag, ok := binding.Field.Tag().Lookup("graphson"); ok && tag != "-" {
+			if enc := ext.DecoratorOfStructField(binding.Encoder, tag); enc != nil {
+				binding.Encoder = enc
+			}
+		}
+	}
+}
+
+// CreateEncoder returns a value encoder for type.
+func (ext encodeExtension) CreateEncoder(typ reflect2.Type) jsoniter.ValEncoder {
+	if enc := ext.EncoderOfRegistered(typ); enc != nil {
+		return enc
+	}
+	if enc := ext.EncoderOfNative(typ); enc != nil {
+		return enc
+	}
+	switch typ.Kind() {
+	case reflect.Map:
+		return ext.EncoderOfMap(typ)
+	default:
+		return nil
+	}
+}
+
+// DecorateEncoder decorates an passed in value encoder for type.
+func (ext encodeExtension) DecorateEncoder(typ reflect2.Type, enc jsoniter.ValEncoder) jsoniter.ValEncoder {
+	if enc := ext.DecoratorOfRegistered(enc); enc != nil {
+		return enc
+	}
+	if enc := ext.DecoratorOfMarshaler(typ, enc); enc != nil {
+		return enc
+	}
+	if enc := ext.DecoratorOfTyper(typ, enc); enc != nil {
+		return enc
+	}
+	if enc := ext.DecoratorOfNative(typ, enc); enc != nil {
+		return enc
+	}
+	switch typ.Kind() {
+	case reflect.Ptr, reflect.Interface, reflect.Struct:
+		return enc
+	case reflect.Array:
+		return ext.DecoratorOfArray(enc)
+	case reflect.Slice:
+		return ext.DecoratorOfSlice(typ, enc)
+	case reflect.Map:
+		return ext.DecoratorOfMap(enc)
+	default:
+		return ext.EncoderOfError("graphson: unsupported type: " + typ.String())
+	}
+}