Added Remove and FromString

Author: linkdotnet

stringbuilder.go

@@ -1,5 +1,7 @@
 package Text
 
+import "fmt"
+
 type StringBuilder struct {
 	data     []rune
 	position int
@@ -10,6 +12,14 @@ func NewStringBuilder(initialCapacity int) *StringBuilder {
 	return &StringBuilder{data: make([]rune, initialCapacity)}
 }
 
+// Creates a new instance of the StringBuilder with a preallocated text
+func NewFromString(text string) *StringBuilder {
+	return &StringBuilder{
+		data:     []rune(text),
+		position: len(text),
+	}
+}
+
 // Appends a text to the StringBuilder instance
 func (s *StringBuilder) Append(text string) {
 	newLen := s.position + len(text)
@@ -48,6 +58,33 @@ func (s *StringBuilder) ToString() string {
 	return string(s.data[:s.position])
 }
 
+func (s *StringBuilder) Remove(start int, length int) error {
+	if start >= s.position {
+		return fmt.Errorf("start is after the end of the string")
+	}
+	if start < 0 {
+		return fmt.Errorf("start can't be a negative value")
+	}
+	if length < 0 {
+		return fmt.Errorf("length can't be a negative value")
+	}
+
+	endIndex := start + length - 1
+
+	if endIndex > s.position {
+		return fmt.Errorf("can't delete after the end of the string")
+	}
+
+	if length == 0 {
+		return nil
+	}
+
+	s.data = append(s.data[:start], s.data[endIndex])
+	s.position -= length
+
+	return nil
+}
+
 func (s *StringBuilder) grow(lenToAdd int) {
 	// Grow times 2 until lenToAdd fits
 	newLen := cap(s.data)

stringbuilder_test.go

@@ -45,3 +45,65 @@ func TestAppendRune(t *testing.T) {
 		t.Errorf("Actual %q, Expected: %q", result, expected)
 	}
 }
+
+func TestToStringEmptyBuilder(t *testing.T) {
+	sb := StringBuilder{}
+
+	if result := sb.ToString(); result != "" {
+		t.Errorf("String should be empty but was: %q", result)
+	}
+}
+
+func TestNewFromString(t *testing.T) {
+	const expected string = "Hello"
+
+	sb := NewFromString(expected)
+
+	if result := sb.ToString(); result != expected {
+		t.Errorf("Actual %q, Expected: %q", result, expected)
+	}
+}
+
+func TestRemovePartOfString(t *testing.T) {
+	sb := NewFromString("Hello")
+
+	if err := sb.Remove(3, 2); err != nil {
+		t.Errorf("Remove threw an error: %v", err)
+	}
+
+	if result := sb.ToString(); result != "Hel" {
+		t.Errorf("Actual %q, Expected: %q", result, "Hel")
+	}
+}
+
+func TestRemoveWhenStartIndexOutOfBounds(t *testing.T) {
+	sb := NewFromString("Hello")
+
+	if err := sb.Remove(100, 1); err == nil {
+		t.Error("Should throw error but did not")
+	}
+}
+
+func TestRemoveWhenStartIndexNegative(t *testing.T) {
+	sb := NewFromString("Hello")
+
+	if err := sb.Remove(-1, 1); err == nil {
+		t.Error("Should throw error but did not")
+	}
+}
+
+func TestRemoveWhenLengthNegative(t *testing.T) {
+	sb := NewFromString("Hello")
+
+	if err := sb.Remove(1, -1); err == nil {
+		t.Error("Should throw error but did not")
+	}
+}
+
+func TestRemoveWhenEndIndexOutOfBounds(t *testing.T) {
+	sb := NewFromString("Hello")
+
+	if err := sb.Remove(4, 4); err == nil {
+		t.Error("Should throw error but did not")
+	}
+}