Adding lo.WaitFor (#269)

* feat(concurrency): adding lo.WaitFor

README.md

@@ -273,6 +273,7 @@ Concurrency helpers:
 - [Synchronize](#synchronize)
 - [Async](#async)
 - [Transaction](#transaction)
+- [WaitFor](#waitfor)
 
 Error handling:
 
@@ -3004,6 +3005,38 @@ _, _ = transaction.Process(-5)
 // rollback 1
 ```
 
+### WaitFor
+
+Runs periodically until a condition is validated.
+
+```go
+alwaysTrue := func(i int) bool { return true }
+alwaysFalse := func(i int) bool { return false }
+laterTrue := func(i int) bool {
+    return i > 5
+}
+
+iterations, duration, ok := lo.WaitFor(alwaysTrue, 10*time.Millisecond, time.Millisecond)
+// 1
+// 0ms
+// true
+
+iterations, duration, ok := lo.WaitFor(alwaysFalse, 10*time.Millisecond, time.Millisecond)
+// 10
+// 10ms
+// false
+
+iterations, duration, ok := lo.WaitFor(laterTrue, 10*time.Millisecond, time.Millisecond)
+// 7
+// 7ms
+// true
+
+iterations, duration, ok := lo.WaitFor(laterTrue, 10*time.Millisecond, 5*time.Millisecond)
+// 2
+// 10ms
+// false
+```
+
 ### Validate
 
 Helper function that creates an error when a condition is not met.

concurrency.go

@@ -1,6 +1,9 @@
 package lo
 
-import "sync"
+import (
+	"sync"
+	"time"
+)
 
 type synchronize struct {
 	locker sync.Locker
@@ -93,3 +96,35 @@ func Async6[A, B, C, D, E, F any](f func() (A, B, C, D, E, F)) <-chan Tuple6[A,
 	}()
 	return ch
 }
+
+// WaitFor runs periodically until a condition is validated.
+func WaitFor(condition func(i int) bool, maxDuration time.Duration, tick time.Duration) (int, time.Duration, bool) {
+	if condition(0) {
+		return 1, 0, true
+	}
+
+	start := time.Now()
+
+	timer := time.NewTimer(maxDuration)
+	ticker := time.NewTicker(tick)
+
+	defer func() {
+		timer.Stop()
+		ticker.Stop()
+	}()
+
+	i := 1
+
+	for {
+		select {
+		case <-timer.C:
+			return i, time.Since(start), false
+		case <-ticker.C:
+			if condition(i) {
+				return i + 1, time.Since(start), true
+			}
+
+			i++
+		}
+	}
+}

concurrency_test.go

@@ -212,3 +212,47 @@ func TestAsyncX(t *testing.T) {
 		}
 	}
 }
+
+func TestWaitFor(t *testing.T) {
+	t.Parallel()
+	testWithTimeout(t, 100*time.Millisecond)
+	is := assert.New(t)
+
+	alwaysTrue := func(i int) bool { return true }
+	alwaysFalse := func(i int) bool { return false }
+
+	iter, duration, ok := WaitFor(alwaysTrue, 10*time.Millisecond, time.Millisecond)
+	is.Equal(1, iter)
+	is.Equal(time.Duration(0), duration)
+	is.True(ok)
+	iter, duration, ok = WaitFor(alwaysFalse, 10*time.Millisecond, 4*time.Millisecond)
+	is.Equal(3, iter)
+	is.InEpsilon(10*time.Millisecond, duration, float64(500*time.Microsecond))
+	is.False(ok)
+
+	laterTrue := func(i int) bool {
+		return i >= 5
+	}
+
+	iter, duration, ok = WaitFor(laterTrue, 10*time.Millisecond, time.Millisecond)
+	is.Equal(6, iter)
+	is.InEpsilon(6*time.Millisecond, duration, float64(500*time.Microsecond))
+	is.True(ok)
+	iter, duration, ok = WaitFor(laterTrue, 10*time.Millisecond, 5*time.Millisecond)
+	is.Equal(2, iter)
+	is.InEpsilon(10*time.Millisecond, duration, float64(500*time.Microsecond))
+	is.False(ok)
+
+	counter := 0
+
+	alwaysFalse = func(i int) bool {
+		is.Equal(counter, i)
+		counter++
+		return false
+	}
+
+	iter, duration, ok = WaitFor(alwaysFalse, 10*time.Millisecond, time.Millisecond)
+	is.Equal(10, iter)
+	is.InEpsilon(10*time.Millisecond, duration, float64(500*time.Microsecond))
+	is.False(ok)
+}