Add optional

Wrapper container with easy to understand helper methods

datastructure/optional/optional.go

@@ -0,0 +1,108 @@
+package optional
+
+import (
+	"sync"
+)
+
+// Optional is a type that may or may not contain a non-nil value.
+type Optional[T any] struct {
+	value *T
+	mu    sync.RWMutex // Ensures thread-safety similar to the Java implementation's value-based behavior
+}
+
+// Empty returns an empty Optional instance.
+func Empty[T any]() Optional[T] {
+	return Optional[T]{}
+}
+
+// Of returns an Optional with a non-nil value.
+func Of[T any](value T) Optional[T] {
+	return Optional[T]{value: &value}
+}
+
+// OfNullable returns an Optional for a given value, which may be nil.
+func OfNullable[T any](value *T) Optional[T] {
+	if value == nil {
+		return Empty[T]()
+	}
+	return Optional[T]{value: value}
+}
+
+// IsPresent checks if there is a value present.
+func (o Optional[T]) IsPresent() bool {
+	o.mu.RLock()
+	defer o.mu.RUnlock()
+
+	return o.value != nil
+}
+
+// IsEmpty checks if the Optional is empty.
+func (o Optional[T]) IsEmpty() bool {
+	return !o.IsPresent()
+}
+
+// IfPresent performs the given action with the value if a value is present.
+func (o Optional[T]) IfPresent(action func(value T)) {
+	o.mu.RLock()
+	defer o.mu.RUnlock()
+
+	if o.value != nil {
+		action(*o.value)
+	}
+}
+
+// IfPresentOrElse performs the action with the value if present, otherwise performs the empty-based action.
+func (o Optional[T]) IfPresentOrElse(action func(value T), emptyAction func()) {
+	o.mu.RLock()
+	defer o.mu.RUnlock()
+
+	if o.value != nil {
+		action(*o.value)
+	} else {
+		emptyAction()
+	}
+}
+
+// Get returns the value if present, otherwise panics.
+func (o Optional[T]) Get() T {
+	o.mu.RLock()
+	defer o.mu.RUnlock()
+
+	if o.value == nil {
+		panic("Optional.Get: no value present")
+	}
+	return *o.value
+}
+
+// OrElse returns the value if present, otherwise returns other.
+func (o Optional[T]) OrElse(other T) T {
+	o.mu.RLock()
+	defer o.mu.RUnlock()
+
+	if o.value != nil {
+		return *o.value
+	}
+	return other
+}
+
+// OrElseGet returns the value if present, otherwise invokes supplier and returns the result.
+func (o Optional[T]) OrElseGet(supplier func() T) T {
+	o.mu.RLock()
+	defer o.mu.RUnlock()
+
+	if o.value != nil {
+		return *o.value
+	}
+	return supplier()
+}
+
+// OrElseThrow returns the value if present, otherwise returns an error.
+func (o Optional[T]) OrElseThrow(errorSupplier func() error) (T, error) {
+	o.mu.RLock()
+	defer o.mu.RUnlock()
+
+	if o.value == nil {
+		return *new(T), errorSupplier()
+	}
+	return *o.value, nil
+}

datastructure/optional/optional_test.go

@@ -0,0 +1,91 @@
+package optional
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/duke-git/lancet/v2/internal"
+)
+
+func TestEmpty(t *testing.T) {
+	assert := internal.NewAssert(t, "TestEmpty")
+	opt := Empty[int]()
+
+	assert.ShouldBeFalse(opt.IsPresent())
+}
+
+func TestOf(t *testing.T) {
+	assert := internal.NewAssert(t, "TestOf")
+	value := 42
+	opt := Of(value)
+
+	assert.ShouldBeTrue(opt.IsPresent())
+	assert.Equal(opt.Get(), value)
+}
+
+func TestOfNullable(t *testing.T) {
+	assert := internal.NewAssert(t, "TestOfNullable")
+	var value *int = nil
+	opt := OfNullable(value)
+
+	assert.ShouldBeFalse(opt.IsPresent())
+
+	value = new(int)
+	*value = 42
+	opt = OfNullable(value)
+
+	assert.ShouldBeTrue(opt.IsPresent())
+}
+
+func TestOrElse(t *testing.T) {
+	assert := internal.NewAssert(t, "TestOrElse")
+	optEmpty := Empty[int]()
+	defaultValue := 100
+
+	val := optEmpty.OrElse(defaultValue)
+	assert.Equal(val, defaultValue)
+
+	optWithValue := Of(42)
+	val = optWithValue.OrElse(defaultValue)
+	assert.Equal(val, 42)
+}
+
+func TestOrElseGet(t *testing.T) {
+	assert := internal.NewAssert(t, "TestOrElseGet")
+	optEmpty := Empty[int]()
+	supplier := func() int { return 100 }
+
+	val := optEmpty.OrElseGet(supplier)
+	assert.Equal(val, supplier())
+}
+
+func TestOrElseThrow(t *testing.T) {
+	assert := internal.NewAssert(t, "TestOrElseThrow")
+	optEmpty := Empty[int]()
+	_, err := optEmpty.OrElseThrow(func() error { return errors.New("no value") })
+
+	assert.Equal(err.Error(), "no value")
+
+	optWithValue := Of(42)
+	val, err := optWithValue.OrElseThrow(func() error { return errors.New("no value") })
+
+	assert.IsNil(err)
+	assert.Equal(val, 42)
+}
+
+func TestIfPresent(t *testing.T) {
+	assert := internal.NewAssert(t, "TestIfPresent")
+	called := false
+	action := func(value int) { called = true }
+
+	optEmpty := Empty[int]()
+	optEmpty.IfPresent(action)
+
+	assert.ShouldBeFalse(called)
+
+	called = false // Reset for next test
+	optWithValue := Of(42)
+	optWithValue.IfPresent(action)
+
+	assert.ShouldBeTrue(called)
+}

internal/assert.go

@@ -36,6 +36,20 @@ func (a *Assert) Equal(expected, actual any) {
 	}
 }
 
+// ShouldBeFalse check if expected is false
+func (a *Assert) ShouldBeFalse(actual any) {
+	if compare(false, actual) != compareEqual {
+		makeTestFailed(a.T, a.CaseName, false, actual)
+	}
+}
+
+// ShouldBeTrue check if expected is true
+func (a *Assert) ShouldBeTrue(actual any) {
+	if compare(true, actual) != compareEqual {
+		makeTestFailed(a.T, a.CaseName, true, actual)
+	}
+}
+
 // NotEqual check if expected is not equal with actual
 func (a *Assert) NotEqual(expected, actual any) {
 	if compare(expected, actual) == compareEqual {