add cpf formatter

cpf/formatter.go

@@ -0,0 +1,38 @@
+package cpf
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/brazilian-utils/brutils-go/helpers"
+)
+
+var dotIndexes = []int{3, 6}
+var hyphenIndexes = []int{9}
+
+// Format returns the CPF with all the "." and "-"
+func Format(cpf string) string {
+	cpfNumbers := helpers.OnlyNumbers(cpf)
+
+	// Truncate the CPF to its maximum size
+	if len(cpfNumbers) > cpfSize {
+		cpfNumbers = cpfNumbers[:cpfSize]
+	}
+
+	return format(cpfNumbers)
+}
+
+func format(nomalizedCpf string) string {
+	buf := bytes.Buffer{}
+	for index, character := range nomalizedCpf {
+		if helpers.ContainsInt(dotIndexes, index) {
+			buf.WriteString(".")
+		}
+		if helpers.ContainsInt(hyphenIndexes, index) {
+			buf.WriteString("-")
+		}
+		buf.WriteString(fmt.Sprintf("%c", character))
+	}
+
+	return buf.String()
+}

cpf/formatter_test.go

@@ -0,0 +1,35 @@
+package cpf_test
+
+import (
+	"testing"
+
+	"github.com/brazilian-utils/brutils-go/cpf"
+)
+
+var formatTestValues = []struct {
+	input    string
+	expected string
+}{
+	{"", ""},
+	{"9", "9"},
+	{"94", "94"},
+	{"943", "943"},
+	{"9438", "943.8"},
+	{"94389", "943.89"},
+	{"943895", "943.895"},
+	{"9438957", "943.895.7"},
+	{"94389575", "943.895.75"},
+	{"943895751", "943.895.751"},
+	{"9438957510", "943.895.751-0"},
+	{"94389575104", "943.895.751-04"},
+	{"94389575104000000", "943.895.751-04"},
+	{"943.?ABC895.751-04abc", "943.895.751-04"},
+}
+
+func TestFormat(t *testing.T) {
+	for _, table := range formatTestValues {
+		if res := cpf.Format(table.input); res != table.expected {
+			t.Errorf("Failing for %v \t Expected: %v | Received: %v", table.input, table.expected, res)
+		}
+	}
+}