added: email validation rule

email.go

@@ -0,0 +1,17 @@
+package validator
+
+const (
+	// Email represents the rule name which will be used to find the default error message.
+	Email = "email"
+	// EmailMsg is the default error message format for fields with the email validation rule.
+	EmailMsg = "%s is not valid"
+	// EmailRegex is the default pattern to validate email field by RFC 5322 rule.
+	EmailRegex = "(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|\"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*\")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\\[(?:(?:(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9]))\\.){3}(?:(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9])|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\\])"
+)
+
+// Email checks the value of s under validation must match the EmailRegex regular expression.
+func (v *Validator) Email(s, field, msg string) *Validator {
+	v.RegexMatches(s, EmailRegex, field, v.msg(Email, msg, field))
+
+	return v
+}

email_test.go

@@ -0,0 +1,78 @@
+package validator
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestValidator_Email(t *testing.T) {
+	tests := []struct {
+		name        string
+		field       string
+		value       string
+		isPassed    bool
+		message     string
+		expectedMsg string
+	}{
+		{
+			name:        "test an empty string value will fail email validation",
+			field:       "email",
+			value:       "",
+			isPassed:    false,
+			message:     "email is not valid",
+			expectedMsg: "email is not valid",
+		},
+		{
+			name:        "test an empty space string value will fail email validation",
+			field:       "email_address",
+			value:       " ",
+			isPassed:    false,
+			message:     "email_address is not valid",
+			expectedMsg: "email_address is not valid",
+		},
+		{
+			name:        "test a wrong string value will fail email validation",
+			field:       "email",
+			value:       "09377475856",
+			isPassed:    false,
+			message:     "email is not valid",
+			expectedMsg: "email is not valid",
+		},
+		{
+			name:        "test a wrong string value will fail email validation",
+			field:       "email",
+			value:       "^$*me%$e.com",
+			isPassed:    false,
+			message:     "email is not valid",
+			expectedMsg: "email is not valid",
+		},
+		{
+			name:        "test a correct email string value will pass validation",
+			field:       "email",
+			value:       "[email protected]",
+			isPassed:    true,
+			message:     "",
+			expectedMsg: "",
+		},
+	}
+
+	for _, test := range tests {
+		v := New()
+
+		v.Email(test.value, test.field, test.message)
+
+		assert.Equal(t, test.isPassed, v.IsPassed())
+
+		if !test.isPassed {
+			assert.Equalf(
+				t,
+				test.expectedMsg,
+				v.Errors()[test.field],
+				"assertion failed, expectedMsg: %s, validatorMsg: %s",
+				test.expectedMsg,
+				v.Errors()[test.field],
+			)
+		}
+	}
+}

validator.go

@@ -36,6 +36,7 @@ var (
 		Between:   BetweenMsg,
 		NotExists: NotExistsMsg,
 		Regex:     RegexMsg,
+		Email:     EmailMsg,
 	}
 
 	// ErrMethodMessageNotFound is the default message when a method does not have any error message on methodToErrorMessage.