Add "oneof" tag value

README.md

@@ -96,6 +96,7 @@ You set the validation rules following the "validate:" tag according to the rule
 | min               | Check whether value is greater than or equal to the specified value <br> e.g. `validate:"min=1"` |
 | max               | Check whether value is less than or equal to the specified value <br> e.g. `validate:"max=100"` |
 | len 			    | Check whether the length of the value is equal to the specified value <br> e.g. `validate:"len=10"` |
+| oneof             | Check whether value is included in the specified values <br> e.g. `validate:"oneof=male female prefer_not_to"` |
 
 ## License
 [MIT License](./LICENSE)

csv_test.go

@@ -193,6 +193,41 @@ func TestCSV_Decode(t *testing.T) {
 			t.Errorf("CSV.Decode() mismatch (-got +want):\n%s", diff)
 		}
 	})
+
+	t.Run("validate oneof: success case", func(t *testing.T) {
+		t.Parallel()
+
+		input := `id,gender
+1,male
+2,female
+3,prefer_not_to
+`
+		c, err := NewCSV(bytes.NewBufferString(input))
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		type person struct {
+			ID     int    // no validate
+			Gender string `validate:"oneof=male female prefer_not_to"`
+		}
+
+		people := make([]person, 0)
+		errs := c.Decode(&people)
+		if len(errs) != 0 {
+			t.Errorf("CSV.Decode() got errors: %v", errs)
+		}
+
+		want := []person{
+			{ID: 1, Gender: "male"},
+			{ID: 2, Gender: "female"},
+			{ID: 3, Gender: "prefer_not_to"},
+		}
+
+		if diff := cmp.Diff(people, want); diff != "" {
+			t.Errorf("CSV.Decode() mismatch (-got +want):\n%s", diff)
+		}
+	})
 }
 
 func Test_ErrCheck(t *testing.T) {
@@ -346,4 +381,43 @@ func Test_ErrCheck(t *testing.T) {
 			}
 		}
 	})
+
+	t.Run("validate oneof: error case", func(t *testing.T) {
+		t.Parallel()
+
+		input := `id,gender
+1,smale
+2,child
+3,prefer_not_tooa
+`
+
+		c, err := NewCSV(bytes.NewBufferString(input))
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		type person struct {
+			ID     int    // no validate
+			Gender string `validate:"oneof=male female prefer_not_to"`
+		}
+
+		people := make([]person, 0)
+		errs := c.Decode(&people)
+		for i, err := range errs {
+			switch i {
+			case 0:
+				if err.Error() != "line:2 column gender: target is not one of the values: oneof=male female prefer_not_to, value=smale" {
+					t.Errorf("CSV.Decode() got errors: %v", err)
+				}
+			case 1:
+				if err.Error() != "line:3 column gender: target is not one of the values: oneof=male female prefer_not_to, value=child" {
+					t.Errorf("CSV.Decode() got errors: %v", err)
+				}
+			case 2:
+				if err.Error() != "line:4 column gender: target is not one of the values: oneof=male female prefer_not_to, value=prefer_not_tooa" {
+					t.Errorf("CSV.Decode() got errors: %v", err)
+				}
+			}
+		}
+	})
 }

errors.go

@@ -5,6 +5,11 @@ import "errors"
 var (
 	// ErrStructSlicePointer is returned when the value is not a pointer to a struct slice.
 	ErrStructSlicePointer = errors.New("value is not a pointer to a struct slice")
+	// ErrInvalidOneOfFormat is returned when the target is not one of the values.
+	ErrInvalidOneOfFormat = errors.New("target is not one of the values")
+	// ErrInvalidThresholdFormat is returned when the threshold value is not an integer.
+	ErrInvalidThresholdFormat = errors.New("threshold format is invalid")
+
 	// ErrInvalidBoolean is returned when the target is not a boolean.
 	ErrInvalidBoolean = errors.New("target is not a boolean")
 	// ErrInvalidAlphabet is returned when the target is not an alphabetic character.
@@ -19,8 +24,6 @@ var (
 	ErrEqual = errors.New("target is not equal to the threshold value")
 	// ErrInvalidThreshold is returned when the target is not greater than the value.
 	ErrInvalidThreshold = errors.New("threshold value is invalid")
-	// ErrInvalidThresholdFormat is returned when the threshold value is not an integer.
-	ErrInvalidThresholdFormat = errors.New("threshold format is invalid")
 	// ErrNotEqual is returned when the target is equal to the value.
 	ErrNotEqual = errors.New("target is equal to threshold the value")
 	// ErrGreaterThan is returned when the target is not greater than the value.
@@ -37,4 +40,6 @@ var (
 	ErrMax = errors.New("target is greater than the maximum value")
 	// ErrLength is returned when the target length is not equal to the value.
 	ErrLength = errors.New("target length is not equal to the threshold value")
+	// ErrOneOf is returned when the target is not one of the values.
+	ErrOneOf = errors.New("target is not one of the values")
 )

parser.go

@@ -121,6 +121,13 @@ func parseValidateTag(tags string) (validators, error) {
 				return nil, err
 			}
 			validatorList = append(validatorList, newLengthValidator(threshold))
+
+		case strings.HasPrefix(t, oneOfTagValue.String()):
+			oneOf, err := parseOneOf(t)
+			if err != nil {
+				return nil, err
+			}
+			validatorList = append(validatorList, newOneOfValidator(oneOf))
 		}
 	}
 	return validatorList, nil
@@ -140,3 +147,14 @@ func parseThreshold(tagValue string) (float64, error) {
 	}
 	return 0, fmt.Errorf("%w: %s", ErrInvalidThresholdFormat, tagValue)
 }
+
+// parseOneOf parses the oneOf value.
+// tagValue is the value of the struct tag. e.g. oneof=male female prefer_not_to
+func parseOneOf(tagValue string) ([]string, error) {
+	parts := strings.Split(tagValue, "=")
+
+	if len(parts) == 2 {
+		return strings.Split(parts[1], " "), nil
+	}
+	return nil, fmt.Errorf("%w: %s", ErrInvalidOneOfFormat, tagValue)
+}

tag.go

@@ -40,6 +40,8 @@ const (
 	maxTagValue tagValue = "max"
 	// lengthTagValue is the struct tag name for length fields.
 	lengthTagValue tagValue = "len"
+	// oneOfTagValue is the struct tag name for one of fields.
+	oneOfTagValue tagValue = "oneof"
 )
 
 // String returns the string representation of the tag.

validation.go

@@ -3,6 +3,7 @@ package csv
 import (
 	"fmt"
 	"strconv"
+	"strings"
 
 	"github.com/rivo/uniseg"
 )
@@ -382,3 +383,28 @@ func (l *lengthValidator) Do(target any) error {
 	}
 	return nil
 }
+
+// oneOfValidator is a struct that contains the validation rules for a one of column.
+type oneOfValidator struct {
+	oneOf []string
+}
+
+// newOneOfValidator returns a new oneOfValidator.
+func newOneOfValidator(oneOf []string) *oneOfValidator {
+	return &oneOfValidator{oneOf: oneOf}
+}
+
+// Do validates the target is one of the oneOf values.
+func (o *oneOfValidator) Do(target any) error {
+	v, ok := target.(string)
+	if !ok {
+		return fmt.Errorf("%w: value=%v", ErrOneOf, target) //nolint
+	}
+
+	for _, s := range o.oneOf {
+		if v == s {
+			return nil
+		}
+	}
+	return fmt.Errorf("%w: oneof=%s, value=%v", ErrOneOf, strings.Join(o.oneOf, " "), target) //nolint
+}