add json validation rule

go.mod

@@ -4,13 +4,13 @@ go 1.21
 
 require (
 	github.com/gofrs/uuid v4.4.0+incompatible
+	github.com/pkg/errors v0.9.1
 	github.com/stretchr/testify v1.8.4
 	golang.org/x/net v0.21.0
 )
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	golang.org/x/text v0.14.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect

go.sum

@@ -8,8 +8,6 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
-golang.org/x/net v0.20.0 h1:aCL9BSgETF1k+blQaYUBx9hJ9LOGP3gAVemcZlf1Kpo=
-golang.org/x/net v0.20.0/go.mod h1:z8BVo6PvndSri0LbOE3hAn0apkU+1YvI6E70E9jsnvY=
 golang.org/x/net v0.21.0 h1:AQyQV4dYCvJ7vGmJyKki9+PBdyvhkSd8EIx/qb0AYv4=
 golang.org/x/net v0.21.0/go.mod h1:bIjVDfnllIU7BJ2DNgfnXvpSvtn8VRwhlsaeUTyUS44=
 golang.org/x/text v0.14.0 h1:ScX5w1eTa3QqT8oi6+ziP7dTV1S2+ALU0bI+0zXKWiQ=

json.go

@@ -0,0 +1,97 @@
+package validator
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+)
+
+type JSON struct {
+	message string
+
+	whenFunc  WhenFunc
+	skipEmpty bool
+	skipError bool
+}
+
+func NewJSON() *JSON {
+	return &JSON{
+		message: "Must be a valid JSON",
+	}
+}
+
+func (j *JSON) ValidateValue(_ context.Context, value any) error {
+	var bytes []byte
+
+	switch v := value.(type) {
+	case string:
+		bytes = []byte(v)
+	case *string:
+		bytes = []byte(*v)
+	case []byte:
+		bytes = v
+	case *[]byte:
+		bytes = *v
+	case json.RawMessage:
+		bytes = v
+	case *json.RawMessage:
+		bytes = *v
+	case fmt.Stringer:
+		if i, ok := v.(fmt.Stringer); ok {
+			bytes = []byte(i.String())
+		}
+	default:
+		return NewResult().WithError(NewValidationError(j.message))
+	}
+
+	if isValid := json.Valid(bytes); !isValid {
+		return NewResult().WithError(NewValidationError(j.message))
+	}
+
+	return nil
+}
+
+func (j *JSON) When(v WhenFunc) *JSON {
+	rc := *j
+	rc.whenFunc = v
+
+	return &rc
+}
+
+func (j *JSON) when() WhenFunc {
+	return j.whenFunc
+}
+
+func (j *JSON) setWhen(v WhenFunc) {
+	j.whenFunc = v
+}
+
+func (j *JSON) SkipOnEmpty() *JSON {
+	rc := *j
+	rc.skipEmpty = true
+
+	return &rc
+}
+
+func (j *JSON) skipOnEmpty() bool {
+	return j.skipEmpty
+}
+
+func (j *JSON) setSkipOnEmpty(v bool) {
+	j.skipEmpty = v
+}
+
+func (j *JSON) SkipOnError() *JSON {
+	rs := *j
+	rs.skipError = true
+
+	return &rs
+}
+
+func (j *JSON) shouldSkipOnError() bool {
+	return j.skipError
+}
+
+func (j *JSON) setSkipOnError(v bool) {
+	j.skipError = v
+}

json_test.go

@@ -0,0 +1,241 @@
+package validator
+
+import (
+	"context"
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+type stringer string
+
+func (s stringer) String() string {
+	return string(s)
+}
+
+func TestJSON_ValidateValue_Successfully(t *testing.T) {
+	// region data provider
+	ctx := context.Background()
+
+	str := `"hello world"`
+	obj := `{"hello":"world"}`
+	arr := `["hello","world"]`
+
+	bytesWithString := []byte(str)
+	bytesWithObject := []byte(obj)
+	bytesWithArray := []byte(arr)
+
+	jsonRawWithString := json.RawMessage(str)
+	jsonRawWithObject := json.RawMessage(obj)
+	jsonRawWithArray := json.RawMessage(arr)
+
+	type args struct {
+		value any
+	}
+	tests := []struct {
+		name string
+		args args
+	}{
+		{
+			name: "stringer with string",
+			args: args{value: stringer(str)},
+		},
+		{
+			name: "string",
+			args: args{value: str},
+		},
+		{
+			name: "string object",
+			args: args{value: obj},
+		},
+		{
+			name: "string array",
+			args: args{value: arr},
+		},
+		{
+			name: "string pointer",
+			args: args{value: &str},
+		},
+		{
+			name: "string pointer object",
+			args: args{value: &obj},
+		},
+		{
+			name: "string pointer array",
+			args: args{value: &arr},
+		},
+		{
+			name: "bytes with string",
+			args: args{value: bytesWithString},
+		},
+		{
+			name: "bytes with object",
+			args: args{value: bytesWithObject},
+		},
+		{
+			name: "bytes with array",
+			args: args{value: bytesWithArray},
+		},
+		{
+			name: "bytes pointer with string",
+			args: args{value: &bytesWithString},
+		},
+		{
+			name: "bytes with object",
+			args: args{value: &bytesWithObject},
+		},
+		{
+			name: "bytes with array",
+			args: args{value: &bytesWithArray},
+		},
+		{
+			name: "json.RawMessage with string",
+			args: args{value: jsonRawWithString},
+		},
+		{
+			name: "json.RawMessage with object",
+			args: args{value: jsonRawWithObject},
+		},
+		{
+			name: "json.RawMessage with array",
+			args: args{value: jsonRawWithArray},
+		},
+		{
+			name: "json.RawMessage pointer with string",
+			args: args{value: &jsonRawWithString},
+		},
+		{
+			name: "json.RawMessage pointer with object",
+			args: args{value: &jsonRawWithObject},
+		},
+		{
+			name: "json.RawMessage pointer with array",
+			args: args{value: &jsonRawWithArray},
+		},
+	}
+	// endregion
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			j := NewJSON()
+			err := j.ValidateValue(ctx, tt.args.value)
+			require.NoError(t, err)
+		})
+	}
+}
+
+func TestJSON_ValidateValue_Failure(t *testing.T) {
+	// region data provider
+	ctx := context.Background()
+
+	str := `hello world`
+	obj := `{hello":"world"`
+	arr := `["hello","world`
+
+	bytesWithString := []byte(str)
+	bytesWithObject := []byte(obj)
+	bytesWithArray := []byte(arr)
+
+	jsonRawWithString := json.RawMessage(str)
+	jsonRawWithObject := json.RawMessage(obj)
+	jsonRawWithArray := json.RawMessage(arr)
+
+	type args struct {
+		value any
+	}
+	tests := []struct {
+		name string
+		args args
+	}{
+		{
+			name: "int",
+			args: args{value: 6},
+		},
+		{
+			name: "stringer with string",
+			args: args{value: stringer(str)},
+		},
+		{
+			name: "string",
+			args: args{value: str},
+		},
+		{
+			name: "string object",
+			args: args{value: obj},
+		},
+		{
+			name: "string array",
+			args: args{value: arr},
+		},
+		{
+			name: "string pointer",
+			args: args{value: &str},
+		},
+		{
+			name: "string pointer object",
+			args: args{value: &obj},
+		},
+		{
+			name: "string pointer array",
+			args: args{value: &arr},
+		},
+		{
+			name: "bytes with string",
+			args: args{value: bytesWithString},
+		},
+		{
+			name: "bytes with object",
+			args: args{value: bytesWithObject},
+		},
+		{
+			name: "bytes with array",
+			args: args{value: bytesWithArray},
+		},
+		{
+			name: "bytes pointer with string",
+			args: args{value: &bytesWithString},
+		},
+		{
+			name: "bytes with object",
+			args: args{value: &bytesWithObject},
+		},
+		{
+			name: "bytes with array",
+			args: args{value: &bytesWithArray},
+		},
+		{
+			name: "json.RawMessage with string",
+			args: args{value: jsonRawWithString},
+		},
+		{
+			name: "json.RawMessage with object",
+			args: args{value: jsonRawWithObject},
+		},
+		{
+			name: "json.RawMessage with array",
+			args: args{value: jsonRawWithArray},
+		},
+		{
+			name: "json.RawMessage pointer with string",
+			args: args{value: &jsonRawWithString},
+		},
+		{
+			name: "json.RawMessage pointer with object",
+			args: args{value: &jsonRawWithObject},
+		},
+		{
+			name: "json.RawMessage pointer with array",
+			args: args{value: &jsonRawWithArray},
+		},
+	}
+	// endregion
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			j := NewJSON()
+			err := j.ValidateValue(ctx, tt.args.value)
+			require.Error(t, err)
+		})
+	}
+}