Remove panic from crdt.Counter (yorkie-team#598)

To prevent stopping the server in the production environment,
the panic methods were replaced with error methods.

Modify test codes for counter

As the panic methods in the counter were replaced,
the related test codes also were modified.

api/converter/from_bytes.go

@@ -267,12 +267,19 @@ func fromJSONCounter(pbCnt *api.JSONElement_Counter) (*crdt.Counter, error) {
 	if err != nil {
 		return nil, err
 	}
+	counterValue, err := crdt.CounterValueFromBytes(counterType, pbCnt.Value)
+	if err != nil {
+		return nil, err
+	}
 
-	counter := crdt.NewCounter(
+	counter, err := crdt.NewCounter(
 		counterType,
-		crdt.CounterValueFromBytes(counterType, pbCnt.Value),
+		counterValue,
 		createdAt,
 	)
+	if err != nil {
+		return nil, err
+	}
 	counter.SetMovedAt(movedAt)
 	counter.SetRemovedAt(removedAt)
 

api/converter/from_pb.go

@@ -737,11 +737,20 @@ func fromElement(pbElement *api.JSONElementSimple) (crdt.Element, error) {
 		if err != nil {
 			return nil, err
 		}
-		return crdt.NewCounter(
+		counterValue, err := crdt.CounterValueFromBytes(counterType, pbElement.Value)
+		if err != nil {
+			return nil, err
+		}
+
+		counter, err := crdt.NewCounter(
 			counterType,
-			crdt.CounterValueFromBytes(counterType, pbElement.Value),
+			counterValue,
 			createdAt,
-		), nil
+		)
+		if err != nil {
+			return nil, err
+		}
+		return counter, nil
 	case api.ValueType_VALUE_TYPE_TREE:
 		return BytesToTree(pbElement.Value)
 	}

api/converter/to_bytes.go

@@ -158,11 +158,15 @@ func toCounter(counter *crdt.Counter) (*api.JSONElement, error) {
 	if err != nil {
 		return nil, err
 	}
+	counterValue, err := counter.Bytes()
+	if err != nil {
+		return nil, err
+	}
 
 	return &api.JSONElement{
 		Body: &api.JSONElement_Counter_{Counter: &api.JSONElement_Counter{
 			Type:      pbCounterType,
-			Value:     counter.Bytes(),
+			Value:     counterValue,
 			CreatedAt: ToTimeTicket(counter.CreatedAt()),
 			MovedAt:   ToTimeTicket(counter.MovedAt()),
 			RemovedAt: ToTimeTicket(counter.RemovedAt()),

api/converter/to_pb.go

@@ -435,11 +435,15 @@ func toJSONElementSimple(elem crdt.Element) (*api.JSONElementSimple, error) {
 		if err != nil {
 			return nil, err
 		}
+		counterValue, err := elem.Bytes()
+		if err != nil {
+			return nil, err
+		}
 
 		return &api.JSONElementSimple{
 			Type:      pbCounterType,
 			CreatedAt: ToTimeTicket(elem.CreatedAt()),
-			Value:     elem.Bytes(),
+			Value:     counterValue,
 		}, nil
 	case *crdt.Tree:
 		bytes, err := TreeToBytes(elem)

pkg/document/crdt/counter.go

@@ -18,11 +18,15 @@ package crdt
 
 import (
 	"encoding/binary"
+	"errors"
 	"fmt"
 
 	"github.com/yorkie-team/yorkie/pkg/document/time"
 )
 
+// ErrUnsupportedType is returned when the given type is not supported.
+var ErrUnsupportedType = errors.New("unsupported type")
+
 // CounterType represents any type that can be used as a counter.
 type CounterType int
 
@@ -33,16 +37,16 @@ const (
 )
 
 // CounterValueFromBytes parses the given bytes into value.
-func CounterValueFromBytes(counterType CounterType, value []byte) interface{} {
+func CounterValueFromBytes(counterType CounterType, value []byte) (interface{}, error) {
 	switch counterType {
 	case IntegerCnt:
 		val := int32(binary.LittleEndian.Uint32(value))
-		return int(val)
+		return int(val), nil
 	case LongCnt:
-		return int64(binary.LittleEndian.Uint64(value))
+		return int64(binary.LittleEndian.Uint64(value)), nil
+	default:
+		return nil, ErrUnsupportedType
 	}
-
-	panic("unsupported type")
 }
 
 // Counter represents changeable number data type.
@@ -55,39 +59,47 @@ type Counter struct {
 }
 
 // NewCounter creates a new instance of Counter.
-func NewCounter(valueType CounterType, value interface{}, createdAt *time.Ticket) *Counter {
+func NewCounter(valueType CounterType, value interface{}, createdAt *time.Ticket) (*Counter, error) {
 	switch valueType {
 	case IntegerCnt:
+		intValue, err := castToInt(value)
+		if err != nil {
+			return nil, err
+		}
 		return &Counter{
 			valueType: IntegerCnt,
-			value:     castToInt(value),
+			value:     intValue,
 			createdAt: createdAt,
-		}
+		}, nil
 	case LongCnt:
+		longValue, err := castToLong(value)
+		if err != nil {
+			return nil, err
+		}
 		return &Counter{
 			valueType: LongCnt,
-			value:     castToLong(value),
+			value:     longValue,
 			createdAt: createdAt,
-		}
+		}, nil
+	default:
+		return nil, ErrUnsupportedType
 	}
-
-	panic("unsupported type")
 }
 
 // Bytes creates an array representing the value.
-func (p *Counter) Bytes() []byte {
+func (p *Counter) Bytes() ([]byte, error) {
 	switch val := p.value.(type) {
 	case int32:
 		bytes := [4]byte{}
 		binary.LittleEndian.PutUint32(bytes[:], uint32(val))
-		return bytes[:]
+		return bytes[:], nil
 	case int64:
 		bytes := [8]byte{}
 		binary.LittleEndian.PutUint64(bytes[:], uint64(val))
-		return bytes[:]
+		return bytes[:], nil
+	default:
+		return nil, ErrUnsupportedType
 	}
-
-	panic("unsupported type")
 }
 
 // Marshal returns the JSON encoding of the value.
@@ -146,20 +158,28 @@ func (p *Counter) ValueType() CounterType {
 // than MinInt32, Counter's value type can be changed Integer to Long.
 // Because in golang, int can be either int32 or int64.
 // So we need to assert int to int32.
-func (p *Counter) Increase(v *Primitive) *Counter {
+func (p *Counter) Increase(v *Primitive) (*Counter, error) {
 	if !p.IsNumericType() || !v.IsNumericType() {
-		panic("unsupported type")
+		return nil, ErrUnsupportedType
 	}
 	switch p.valueType {
 	case IntegerCnt:
-		p.value = p.value.(int32) + castToInt(v.value)
+		intValue, err := castToInt(v.value)
+		if err != nil {
+			return nil, err
+		}
+		p.value = p.value.(int32) + intValue
 	case LongCnt:
-		p.value = p.value.(int64) + castToLong(v.value)
+		longValue, err := castToLong(v.value)
+		if err != nil {
+			return nil, err
+		}
+		p.value = p.value.(int64) + longValue
 	default:
-		panic("unsupported type")
+		return nil, ErrUnsupportedType
 	}
 
-	return p
+	return p, nil
 }
 
 // IsNumericType checks for numeric types.
@@ -169,37 +189,37 @@ func (p *Counter) IsNumericType() bool {
 }
 
 // castToInt casts numeric type to int32.
-func castToInt(value interface{}) int32 {
+func castToInt(value interface{}) (int32, error) {
 	switch val := value.(type) {
 	case int32:
-		return val
+		return val, nil
 	case int64:
-		return int32(val)
+		return int32(val), nil
 	case int:
-		return int32(val)
+		return int32(val), nil
 	case float32:
-		return int32(val)
+		return int32(val), nil
 	case float64:
-		return int32(val)
+		return int32(val), nil
 	default:
-		panic("unsupported type")
+		return 0, ErrUnsupportedType
 	}
 }
 
 // castToLong casts numeric type to int64.
-func castToLong(value interface{}) int64 {
+func castToLong(value interface{}) (int64, error) {
 	switch val := value.(type) {
 	case int64:
-		return val
+		return val, nil
 	case int32:
-		return int64(val)
+		return int64(val), nil
 	case int:
-		return int64(val)
+		return int64(val), nil
 	case float32:
-		return int64(val)
+		return int64(val), nil
 	case float64:
-		return int64(val)
+		return int64(val), nil
 	default:
-		panic("unsupported type")
+		return 0, ErrUnsupportedType
 	}
 }