add cpf validation

README.md

@@ -202,6 +202,7 @@ Baked-in Validations
 | tiger192 | TIGER192 hash |
 | semver | Semantic Versioning 2.0.0 |
 | ulid | Universally Unique Lexicographically Sortable Identifier ULID |
+| cpf | Registration of Individuals |
 
 ### Comparisons:
 | Tag | Description |

baked_in.go

@@ -214,6 +214,7 @@ var (
 		"semver":                        isSemverFormat,
 		"dns_rfc1035_label":             isDnsRFC1035LabelFormat,
 		"credit_card":                   isCreditCard,
+		"cpf":                           isCPFFormat,
 	}
 )
 
@@ -2519,3 +2520,39 @@ func isCreditCard(fl FieldLevel) bool {
 	}
 	return (sum % 10) == 0
 }
+
+// isCPFFormat is the validation function for validating if the current field's value is a valid CPF, defined by Federal Revenue of Brazil
+func isCPFFormat(fl FieldLevel) bool {
+	cpfFirstDigitTable := []int{10, 9, 8, 7, 6, 5, 4, 3, 2}
+	cpfSecondDigitTable := []int{11, 10, 9, 8, 7, 6, 5, 4, 3, 2}
+
+	cpf := fl.Field().String()
+	if len(cpf) != 11 {
+		return false
+	}
+
+	firstPart := cpf[0:9]
+	sum := sumDigit(firstPart, cpfFirstDigitTable)
+
+	r1 := sum % 11
+	d1 := 0
+
+	if r1 >= 2 {
+		d1 = 11 - r1
+	}
+
+	secondPart := firstPart + strconv.Itoa(d1)
+
+	dsum := sumDigit(secondPart, cpfSecondDigitTable)
+
+	r2 := dsum % 11
+	d2 := 0
+
+	if r2 >= 2 {
+		d2 = 11 - r2
+	}
+
+	finalPart := fmt.Sprintf("%s%d%d", firstPart, d1, d2)
+	return finalPart == cpf
+}
+

doc.go

@@ -1047,6 +1047,12 @@ This validates that a string value contains a valid ULID value.
 
 	Usage: ulid
 
+Registration of Individuals (CPF)
+
+This validates that a string value contains a valid CPF.
+
+	Usage: cpf
+
 ASCII
 
 This validates that a string value contains only ASCII characters.

translations/en/en.go

@@ -1146,6 +1146,11 @@ func RegisterDefaultTranslations(v *validator.Validate, trans ut.Translator) (er
 			translation: "{0} must be a valid ULID",
 			override:    false,
 		},
+		{
+			tag:         "cpf",
+			translation: "{0} must be a valid CPF",
+			override:    false,
+		},
 		{
 			tag:         "ascii",
 			translation: "{0} must contain only ascii characters",

translations/en/en_test.go

@@ -106,6 +106,7 @@ func TestTranslations(t *testing.T) {
 		UUID4             string            `validate:"uuid4"`
 		UUID5             string            `validate:"uuid5"`
 		ULID              string            `validate:"ulid"`
+		CPF               string            `validate:"cpf"`
 		ASCII             string            `validate:"ascii"`
 		PrintableASCII    string            `validate:"printascii"`
 		MultiByte         string            `validate:"multibyte"`
@@ -334,6 +335,10 @@ func TestTranslations(t *testing.T) {
 			ns:       "Test.ULID",
 			expected: "ULID must be a valid ULID",
 		},
+		{
+			ns:       "Test.CPF",
+			expected: "CPF must be a valid CPF",
+		},
 		{
 			ns:       "Test.ISBN",
 			expected: "ISBN must be a valid ISBN number",

util.go

@@ -286,3 +286,24 @@ func panicIf(err error) {
 		panic(err.Error())
 	}
 }
+
+// Receive a sequence of integers and an array of index. Returns the sum of index values
+// Used for CPF/CNPJ validation
+func sumDigit(s string, table []int) int {
+
+	if len(s) != len(table) {
+		return 0
+	}
+
+	sum := 0
+
+	for i, v := range table {
+		c := string(s[i])
+		d, err := strconv.Atoi(c)
+		if err == nil {
+			sum += v * d
+		}
+	}
+
+	return sum
+}

validator_test.go

@@ -12286,3 +12286,52 @@ func TestMultiOrOperatorGroup(t *testing.T) {
  		}
  	}
  }
+
+func TestCPFField(t *testing.T) {
+	tests := []struct {
+		Value    string `validate:"cpf"`
+		expected bool
+	}{
+		{"33888222044", true}, //249//293
+		{"16814496097", true}, //233 290
+		{"37919050073", true},
+		{"338.882.220-44", false},
+		{"02588789854INVALID", false},
+		{"33888222042", false},
+	}
+
+	validate := New()
+
+	for i, test := range tests {
+		errs := validate.Struct(test)
+		if test.expected {
+			if !IsEqual(errs, nil) {
+				t.Fatalf("Index: %d cpf failed Error: %s", i, errs)
+			}
+		} else {
+			if IsEqual(errs, nil) {
+				t.Fatalf("Index: %d cpf failed Error: %s", i, errs)
+			}
+		}
+	}
+}
+
+func TestSumDigit(t *testing.T) {
+	tests := []struct {
+		sequence string `validate:"cpf"`
+		indexs   []int
+		expected int
+	}{
+		{"338882220", []int{10, 9, 8, 7, 6, 5, 4, 3, 2}, 249},
+		{"3388822204", []int{11, 10, 9, 8, 7, 6, 5, 4, 3, 2}, 293},
+		{"168144960", []int{10, 9, 8, 7, 6, 5, 4, 3, 2}, 233},
+		{"1681449609", []int{11, 10, 9, 8, 7, 6, 5, 4, 3, 2}, 290},
+	}
+
+	for i, test := range tests {
+		result := sumDigit(test.sequence, test.indexs)
+		if !IsEqual(result, test.expected) {
+			t.Fatalf("Index: %d cpf failed. Expected: %d, received: %d", i, test.expected, result)
+		}
+	}
+}