First n string/ Last n string function added

README.md

@@ -46,6 +46,11 @@ A Golang string manipulation utility which have many useful functionality like c
         <td><a href="#toupper-string">ToUpper</a></td>
         <td><a href="#ucfirst-string">UcFirst</a></td>
     </tr>
+     <tr>
+            <td><a href="#firstlength-int-string">First</a></td>
+            <td><a href="#lastlength-int-string">ToUpper</a></td>
+            <td></td>
+        </tr>
 </table>
 
 
@@ -142,6 +147,17 @@ Delimited is variadic function that takes two params delimiter and slice of stri
 You can chain to upper which with make result all uppercase or ToLower which will make result all lower case or Get which will return result as it is.
 
 
+#### First(length int) string
+
+First returns first n characters from provided input. It removes all spaces in string before doing so.
+
+```go
+  fcn := stringy.New("4111 1111 1111 1111")
+  first := fcn.First(4)
+  fmt.Println(first) // 4111
+```
+
+
 #### Get() string
 
 Get simply returns result and can be chained on function which returns StringManipulation interface view above examples
@@ -160,6 +176,17 @@ KebabCase/slugify is variadic function that takes one Param slice of strings nam
 You can chain to upper which with make result all uppercase or ToLower which will make result all lower case or Get which will return result as it is.
 
 
+#### Last(length int) string
+
+Last returns last n characters from provided input. It removes all spaces in string before doing so.
+
+```go
+  lcn := stringy.New("4111 1111 1111 1348")
+  last := lcn.Last(4)
+  fmt.Println(last) // 1348
+```
+
+
 #### LcFirst() string
 
 LcFirst simply returns result by lower casing first letter of string and it can be chained on function which return StringManipulation interface

example/main.go

@@ -66,4 +66,12 @@ func main() {
 	kebabStr := str.KebabCase("?", "")
 	fmt.Println(kebabStr.ToUpper()) // HELLO-MAN-HOW-ARE-YOU
 
+	fcn := stringy.New("4111 1111 1111 1111")
+	first := fcn.First(4)
+	fmt.Println(first) // 4111
+
+	lcn := stringy.New("4111 1111 1111 1348")
+	last := lcn.Last(4)
+	fmt.Println(last) // 1348
+
 }

message.go

@@ -2,14 +2,16 @@ package stringy
 
 // const below are used in packages
 const (
-	First          = "first"
-	Last           = "last"
-	Left           = "left"
-	Right          = "right"
-	Both           = "both"
-	OddError       = "odd number rule provided please provide in even count"
-	SelectCapital  = "([a-z])([A-Z])"
-	ReplaceCapital = "$1 $2"
+	First                = "first"
+	Last                 = "last"
+	Left                 = "left"
+	Right                = "right"
+	Both                 = "both"
+	OddError             = "odd number rule provided please provide in even count"
+	SelectCapital        = "([a-z])([A-Z])"
+	ReplaceCapital       = "$1 $2"
+	LengthError          = "passed length cannot be greater than input length"
+	InvalidLogicalString = "invalid string value to test boolean value"
 )
 
 // False is slice of array for false logical representation in string

stringy.go

@@ -23,8 +23,10 @@ type StringManipulation interface {
 	CamelCase(rule ...string) string
 	ContainsAll(check ...string) bool
 	Delimited(delimiter string, rule ...string) StringManipulation
+	First(length int) string
 	Get() string
 	KebabCase(rule ...string) StringManipulation
+	Last(length int) string
 	LcFirst() string
 	Lines() []string
 	Pad(length int, with, padType string) string
@@ -86,7 +88,7 @@ func (i *input) Boolean() bool {
 	if on {
 		return true
 	}
-	panic(errors.New("invalid string value to test boolean value"))
+	panic(errors.New(InvalidLogicalString))
 }
 
 // CamelCase is variadic function which takes one Param rule i.e slice of strings and it returns
@@ -131,6 +133,16 @@ func (i *input) Delimited(delimiter string, rule ...string) StringManipulation {
 	return i
 }
 
+// First returns first n characters from provided input. It removes all spaces in string before doing so.
+func (i *input) First(length int) string {
+	input := getInput(*i)
+	input = strings.ReplaceAll(input, " ", "")
+	if len(input) < length {
+		panic(errors.New(LengthError))
+	}
+	return input[0:length]
+}
+
 // Get simply returns result and can be chained on function which
 // returns StringManipulation interface
 func (i *input) Get() string {
@@ -150,6 +162,18 @@ func (i *input) KebabCase(rule ...string) StringManipulation {
 	return i
 }
 
+// Last returns last n characters from provided input. It removes all spaces in string before doing so.
+func (i *input) Last(length int) string {
+	input := getInput(*i)
+	input = strings.ReplaceAll(input, " ", "")
+	inputLen := len(input)
+	if len(input) < length {
+		panic(errors.New(LengthError))
+	}
+	start := inputLen - length
+	return input[start:inputLen]
+}
+
 // LcFirst simply returns result by lower casing first letter of string and it can be chained on
 // function which return StringManipulation interface
 func (i *input) LcFirst() string {

stringy_test.go

@@ -158,3 +158,19 @@ func TestInput_UcFirst(t *testing.T) {
 		t.Errorf("Expected: to be %s but got: %s", against, val)
 	}
 }
+
+func TestInput_First(t *testing.T) {
+	fcn := New("4111 1111 1111 1111")
+	against := "4111"
+	if first := fcn.First(4); first != against {
+		t.Errorf("Expected: to be %s but got: %s", against, first)
+	}
+}
+
+func TestInput_Last(t *testing.T) {
+	lcn := New("4111 1111 1111 1348")
+	against := "1348"
+	if last := lcn.Last(4); last != against {
+		t.Errorf("Expected: to be %s but got: %s", against, last)
+	}
+}