feat(helpers): Add more methods (#162)

helpers/helpers.go

@@ -2,6 +2,7 @@ package helpers
 
 import (
 	"encoding/json"
+	"time"
 )
 
 // If returns trueVal if condition is true, otherwise falseVal
@@ -56,6 +57,18 @@ func With[T any](value T, callbacks ...func(T) T) T {
 	return value
 }
 
+// Transform calls the given callback with the given value then return the result.
+//
+// Example:
+//
+//	Transform(1, strconv.Itoa) // "1"
+//	Transform("foo", func(s string) *foo {
+//		return &foo{Name: s}
+//	}) // &foo{Name: "foo"}
+func Transform[T, R any](value T, callback func(T) R) R {
+	return callback(value)
+}
+
 // Pipe is a function that takes a value and returns a value
 //
 //	Pipe(m1, m2, m3)(value) => m3(m2(m1(value)))
@@ -148,3 +161,39 @@ func Scan(src any, dest any) error {
 
 	return json.Unmarshal(bytes, dest)
 }
+
+// Retry retries the given function until it returns nil or the attempts are exhausted.
+func Retry(fn func() error, attempts int, sleeps ...time.Duration) (err error) {
+	var sleep time.Duration
+	if len(sleeps) > 0 {
+		sleep = sleeps[0]
+	}
+
+	for i := 0; i < attempts; i++ {
+		if err = fn(); err == nil {
+			return nil
+		}
+		if sleep > 0 {
+			time.Sleep(sleep)
+		}
+	}
+	return
+}
+
+// Default returns defaultValue if value is zero, otherwise value.
+func Default[T comparable](value T, defaultValue T) T {
+	var zero T
+	if value == zero {
+		return defaultValue
+	}
+	return value
+}
+
+// DefaultWith returns defaultValue if value is zero, otherwise value.
+func DefaultWith[T comparable](value T, defaultValue func() T) T {
+	var zero T
+	if value == zero {
+		return defaultValue()
+	}
+	return value
+}

helpers/helpers_test.go

@@ -2,6 +2,7 @@ package helpers
 
 import (
 	"context"
+	"strconv"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -121,6 +122,15 @@ func TestWhen(t *testing.T) {
 	assert.Equal(t, 18, f3.Age)
 }
 
+func TestTransform(t *testing.T) {
+	got := Transform("foo", func(s string) *foo {
+		return &foo{Name: s}
+	})
+	assert.Equal(t, "foo", got.Name)
+
+	assert.Equal(t, "1", Transform(1, strconv.Itoa))
+}
+
 func TestPipe(t *testing.T) {
 	// pipe functions
 	pipe := Pipe(
@@ -374,3 +384,68 @@ func TestChainWithErr(t *testing.T) {
 	assert.Error(t, err)
 	assert.Equal(t, "02", got)
 }
+
+func TestRetry(t *testing.T) {
+	// success
+	var i int
+	err := Retry(func() error {
+		i++
+		if i < 3 {
+			return assert.AnError
+		}
+		return nil
+	}, 3)
+	assert.Nil(t, err)
+	assert.Equal(t, 3, i)
+
+	// failed
+	err = Retry(func() error {
+		return assert.AnError
+	}, 3)
+	assert.Error(t, err)
+	assert.Equal(t, 3, i)
+}
+
+func TestDefault(t *testing.T) {
+	// string
+	got := Default("", "foo")
+	assert.Equal(t, "foo", got)
+
+	// int
+	got2 := Default(0, 10)
+	assert.Equal(t, 10, got2)
+
+	// struct
+	got3 := Default(foo{}, foo{Name: "bar"})
+	assert.Equal(t, "bar", got3.Name)
+
+	// ptr
+	got4 := Default(nil, &foo{Name: "bar"})
+	assert.Equal(t, "bar", got4.Name)
+}
+
+func TestDefaultWith(t *testing.T) {
+	// string
+	got := DefaultWith("", func() string {
+		return "foo"
+	})
+	assert.Equal(t, "foo", got)
+
+	// int
+	got2 := DefaultWith(0, func() int {
+		return 10
+	})
+	assert.Equal(t, 10, got2)
+
+	// struct
+	got3 := DefaultWith(foo{}, func() foo {
+		return foo{Name: "bar"}
+	})
+	assert.Equal(t, "bar", got3.Name)
+
+	// ptr
+	got4 := DefaultWith(nil, func() *foo {
+		return &foo{Name: "bar"}
+	})
+	assert.Equal(t, "bar", got4.Name)
+}