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app/com/ysoft/concurrent/FutureLock.scala

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+package com.ysoft.concurrent
+
+import java.util.concurrent.atomic.AtomicBoolean
+
+import scala.concurrent.{ExecutionContext, Future}
+
+trait FutureLock[T] {
+  def whenLocked(cannotLock: => Future[T])(implicit executionContext: ExecutionContext): Future[T]
+}
+
+object FutureLock {
+
+  def futureLock[T](lock: AtomicBoolean)(f: => Future[T]): FutureLock[T] = new FutureLock[T]() {
+    override def whenLocked(cannotLock: => Future[T])(implicit executionContext: ExecutionContext): Future[T] = {
+      if (lock.compareAndSet(/*expect = */ false, /*update = */ true)) {
+        try {
+          f.andThen { case _ =>
+            val wasLocked = lock.getAndSet(false)
+            if (!wasLocked) {
+              throw new RuntimeException("The lock was not being held when trying to unlock")
+            }
+          }
+        } catch {
+          case e: Throwable =>
+            // So, the Exception was raised before creation of the Future. As a result, the Future will not relase the lock.
+            // In other words, its our responsibility to release the lock:
+            val wasLocked = lock.getAndSet(false)
+            if (!wasLocked) {
+              throw new RuntimeException("The lock was not being held when throwing the following exception", e)
+            }
+            throw e
+        }
+      } else {
+        cannotLock
+      }
+    }
+  }
+
+
+}