integrate request builder into HTTP client for googleapis support (#159)

builder/body.go

@@ -0,0 +1,116 @@
+package builder
+
+import (
+	"fmt"
+
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/reflect/protoreflect"
+)
+
+func buildSingleFieldBody(msg proto.Message, fieldName string) (proto.Message, error) {
+	msgReflect := msg.ProtoReflect()
+
+	fd, found := findFieldByName(msgReflect, fieldName)
+	if !found || fd == nil {
+		return nil, fmt.Errorf("field %s not found", fieldName)
+	}
+	if !msgReflect.Has(fd) {
+		return nil, fmt.Errorf("field %s is not set", fieldName)
+	}
+
+	val := msgReflect.Get(fd)
+
+	if fd.Kind() == protoreflect.MessageKind {
+		return val.Message().Interface(), nil
+	}
+
+	newMsg := proto.Clone(msg)
+	newMsgReflect := newMsg.ProtoReflect()
+	newMsgReflect.Range(func(f protoreflect.FieldDescriptor, _ protoreflect.Value) bool {
+		if f != fd {
+			newMsgReflect.Clear(f)
+		}
+		return true
+	})
+
+	return newMsg, nil
+}
+
+func buildFullBody(msg proto.Message, usedFieldsPath *usedFields) (proto.Message, error) {
+	var (
+		msgReflect    = msg.ProtoReflect()
+		newMsg        = msgReflect.New().Interface()
+		newMsgReflect = newMsg.ProtoReflect()
+	)
+
+	fields := msgReflect.Descriptor().Fields()
+	for i := 0; i < fields.Len(); i++ {
+		fd := fields.Get(i)
+		fieldName := fd.JSONName()
+
+		if usedFieldsPath.hasTopLevelKey(fieldName) {
+			continue
+		}
+
+		val := msgReflect.Get(fd)
+		if !val.IsValid() {
+			continue
+		}
+
+		// Note: order of the cases is important!
+		switch {
+		case fd.IsList():
+			list := val.List()
+			newList := newMsgReflect.Mutable(fd).List()
+
+			if fd.Kind() == protoreflect.MessageKind {
+				for j := 0; j < list.Len(); j++ {
+					elem, err := buildFullBody(list.Get(j).Message().Interface(), usedFieldsPath)
+					if err != nil {
+						return nil, fmt.Errorf("recursive build full body: %w", err)
+					}
+					newList.Append(protoreflect.ValueOfMessage(elem.ProtoReflect()))
+				}
+			} else {
+				for j := 0; j < list.Len(); j++ {
+					newList.Append(list.Get(j))
+				}
+			}
+
+		case fd.IsMap():
+			var (
+				m        = val.Map()
+				newMap   = newMsgReflect.Mutable(fd).Map()
+				rangeErr error
+			)
+			m.Range(func(k protoreflect.MapKey, v protoreflect.Value) bool {
+				if fd.MapValue().Kind() == protoreflect.MessageKind {
+					elem, err := buildFullBody(v.Message().Interface(), usedFieldsPath)
+					if err != nil {
+						rangeErr = fmt.Errorf("recursive build full body: %w", err)
+						return false
+					}
+					newMap.Set(k, protoreflect.ValueOfMessage(elem.ProtoReflect()))
+				} else {
+					newMap.Set(k, v)
+				}
+				return true
+			})
+			if rangeErr != nil {
+				return nil, fmt.Errorf("map range error: %w", rangeErr)
+			}
+
+		case fd.Kind() == protoreflect.MessageKind:
+			elem, err := buildFullBody(val.Message().Interface(), usedFieldsPath)
+			if err != nil {
+				return nil, fmt.Errorf("recursive build full body: %w", err)
+			}
+			newMsgReflect.Set(fd, protoreflect.ValueOfMessage(elem.ProtoReflect()))
+
+		default:
+			newMsgReflect.Set(fd, val)
+		}
+	}
+
+	return newMsg, nil
+}