refactor the code

Signed-off-by: Ashutosh Kumar <sonasingh46@gmail.com>

Author: sonasingh46

types/nullable.go

@@ -6,16 +6,47 @@ import (
 	"fmt"
 )
 
-type OptionalNullable[T any] struct {
+/*
+
+Usage of NullableOptional Type:
+
+Consider a go type as below:
+type Obj struct{
+	field NullableOptional[<any_go_type>]
+}
+
+1. Check if value is explicitly provided null
+	if obj.field.IsNull() { // explicit null provided }
+
+2. Check if a value is explicitly provided which is not null
+   if obj.field.HasValue() { // some value provided which could be zero value but not null }
+
+Caution:
+
+A zero value should not be read before checking if it hasValue via `HasValue()`.
+For example an empty json object `{}` Marshals to zero value even if it is not
+explicitly provided in JSON.
+
+Limitations:
+
+The conversion of JSON date to NullableOptional type and then converting the
+concrete golang NullableOptional type back to JSON does not result in the original
+JSON for some of the cases meaning the operation is not idempotent.
+
+Refer the test case TestNullableRequiredIdempotency
+*/
+
+type NullableOptional[T any] struct {
 	Value T
-	// Set indicates whether the underlying Value was sent in the request TODO
+	// Set indicates whether the underlying Value was sent in the request.
 	Set bool
-	// Null indicates whether the underlying Value was sent in the request as a literal `null` value. Should only be checked if Set==true TODO
+	// Null indicates whether the underlying Value was sent in the request as a literal `null` value.
+	// Should only be checked if Set==true.
 	Null bool
 }
 
 // UnmarshalJSON implements the Unmarshaler interface.
-func (t *OptionalNullable[T]) UnmarshalJSON(data []byte) error {
+func (t *NullableOptional[T]) UnmarshalJSON(data []byte) error {
 	t.Set = true
 	if bytes.Equal(data, []byte("null")) {
 		t.Null = true
@@ -29,27 +60,58 @@ func (t *OptionalNullable[T]) UnmarshalJSON(data []byte) error {
 }
 
 // MarshalJSON implements the  Marshaler interface.
-func (t OptionalNullable[T]) MarshalJSON() ([]byte, error) {
+func (t NullableOptional[T]) MarshalJSON() ([]byte, error) {
 	if t.Set && t.Null {
 		return []byte("null"), nil
 	}
 	return json.Marshal(t.Value)
 }
 
+// IsNull returns true if the value is explicitly provided `null`
+func (t *NullableOptional[T]) IsNull() bool {
+	return t.Set && t.Null
+}
+
+// HasValue returns true if the value is explicitly provided and is not `null`
+func (t *NullableOptional[T]) HasValue() bool {
+	return t.Set && !t.Null
+}
+
+/*
+
+Usage of Nullable Type:
+
+Consider a go type as below:
+type Obj struct{
+	field Nullable[<any_go_type>]
+}
+
+1. Check if value is explicitly provided null
+	if obj.field.IsNull() { // explicit null provided }
+
+2. Since Nullable type should be used with required fields, it does not have
+   the ability to answer if it was set, assuming it always provided.
+
+Limitations:
+
+The conversion of JSON date to NullableOptional type and then converting the
+concrete golang NullableOptional type back to JSON does not result in the original
+JSON for some of the cases meaning the operation is not idempotent.
+
+Refer the test case TestNullableOptionalIdempotency
+
+*/
+
 // Nullable type which can help distinguish between if a value was explicitly
 // provided `null` in JSON or not
 type Nullable[T any] struct {
 	Value T
-	// Set indicates whether the underlying Value was sent in the request TODO
-	Set bool
-	// Null indicates whether the underlying Value was sent in the request as a literal `null` value. Should only be checked if Set==true TODO
+	// Null indicates whether the underlying Value was sent in the request as a literal `null` value.
 	Null bool
 }
 
 // UnmarshalJSON implements the Unmarshaler interface.
 func (t *Nullable[T]) UnmarshalJSON(data []byte) error {
-	// fmt.Println("UnmarshalJSON")
-	t.Set = true
 	if bytes.Equal(data, []byte("null")) {
 		t.Null = true
 		return nil
@@ -63,22 +125,13 @@ func (t *Nullable[T]) UnmarshalJSON(data []byte) error {
 
 // MarshalJSON implements the  Marshaler interface.
 func (t Nullable[T]) MarshalJSON() ([]byte, error) {
-	if t.Set && t.IsNull() {
+	if t.IsNull() {
 		return []byte("null"), nil
 	}
 	return json.Marshal(t.Value)
 }
 
 // IsNull returns true if the value is explicitly provided `null` in json
 func (t *Nullable[T]) IsNull() bool {
-	return t.Set && t.Null
-}
-
-// HasValue returns true if the value is explicitly provided in json
-func (t *Nullable[T]) HasValue() bool {
-	return t.Set && t.Null
-}
-
-func (t *Nullable[T]) Get() (value T, null bool) {
-	return t.Value, t.IsNull()
+	return t.Null
 }