From b16af62dd6b6e81310134721c72de5061019a68e Mon Sep 17 00:00:00 2001
From: Julian Ladisch <julianladisch@users.noreply.github.com>
Date: Wed, 4 Nov 2020 19:12:50 +0100
Subject: [PATCH] OKAPI-943: GenericCompositeFuture

Coordinate a List<Future<T extends Future <?>>>, provides
all(List<T>), any(List<T>) and join(List<T>) that work like
CompositeFuture#all(List), CompositeFuture#any(List) and
CompositeFuture#join(List) but properly check the
generic type <T extends Future<?>>.

See https://github.com/eclipse-vertx/vert.x/pull/3595 why Vert.x doesn't have this.
---
 okapi-common/pom.xml                          |   5 +
 .../okapi/common/GenericCompositeFuture.java  |  59 ++++++++++
 .../common/GenericCompositeFutureTest.java    | 103 ++++++++++++++++++
 3 files changed, 167 insertions(+)
 create mode 100644 okapi-common/src/main/java/org/folio/okapi/common/GenericCompositeFuture.java
 create mode 100644 okapi-common/src/test/java/org/folio/okapi/common/GenericCompositeFutureTest.java

diff --git a/okapi-common/pom.xml b/okapi-common/pom.xml
index e6e8934ac..98694100b 100644
--- a/okapi-common/pom.xml
+++ b/okapi-common/pom.xml
@@ -71,6 +71,11 @@
       <artifactId>vertx-unit</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.assertj</groupId>
+      <artifactId>assertj-core</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>
diff --git a/okapi-common/src/main/java/org/folio/okapi/common/GenericCompositeFuture.java b/okapi-common/src/main/java/org/folio/okapi/common/GenericCompositeFuture.java
new file mode 100644
index 000000000..9ce00594b
--- /dev/null
+++ b/okapi-common/src/main/java/org/folio/okapi/common/GenericCompositeFuture.java
@@ -0,0 +1,59 @@
+package org.folio.okapi.common;
+
+import io.vertx.core.CompositeFuture;
+import io.vertx.core.Future;
+import io.vertx.core.impl.future.CompositeFutureImpl;
+import java.util.List;
+
+/**
+ * Coordinate a {@code List<Future<T extends Future <?>>>}, provides
+ * {@link #all(List) all(List&lt;T>)}, {@link #any(List) any(List&lt;T>)} and
+ * {@link #join(List) join(List&lt;T>)} that work like
+ * {@link CompositeFuture#all(List)}, {@link CompositeFuture#any(List)} and
+ * {@link CompositeFuture#join(List)} but properly check the generic type
+ * {@code <T extends Future<?>>}.
+ * <p>
+ * See <a href="https://github.com/eclipse-vertx/vert.x/pull/3595">
+ * https://github.com/eclipse-vertx/vert.x/pull/3595</a>
+ * why Vert.x doesn't have this.
+ */
+public interface GenericCompositeFuture {
+  /**
+   * Return a composite future, succeeded when all futures are succeeded,
+   * failed as soon as one of the futures is failed.
+   * <p/>
+   * When the list is empty, the returned future will be already succeeded.
+   * <p/>
+   * This is the same as {@link CompositeFuture#all(List)} but with generic type declaration.
+   */
+  static <T extends Future<?>> CompositeFuture all(List<T> futures) {
+    return CompositeFutureImpl.all(futures.toArray(new Future[futures.size()]));
+  }
+
+  /**
+   * Return a composite future, succeeded as soon as one future is succeeded,
+   * failed when all futures are failed.
+   * <p/>
+   * When the list is empty, the returned future will be already succeeded.
+   * <p/>
+   * This is the same as {@link CompositeFuture#any(List)} but with generic type declaration.
+   */
+  static <T extends Future<?>> CompositeFuture any(List<T> futures) {
+    return CompositeFutureImpl.any(futures.toArray(new Future[futures.size()]));
+  }
+
+  /**
+   * Return a composite future, succeeded when all {@code futures} are succeeded,
+   * failed when any of the {@code futures} is failed.
+   * <p/>
+   * It always waits until all its {@code futures} are completed and will not fail
+   * as soon as one of the {@code futures} fails.
+   * <p/>
+   * When the list is empty, the returned future will be already succeeded.
+   * <p/>
+   * This is the same as {@link CompositeFuture#join(List)} but with generic type declaration.
+   */
+  static <T extends Future<?>> CompositeFuture join(List<T> futures) {
+    return CompositeFutureImpl.join(futures.toArray(new Future[futures.size()]));
+  }
+}
diff --git a/okapi-common/src/test/java/org/folio/okapi/common/GenericCompositeFutureTest.java b/okapi-common/src/test/java/org/folio/okapi/common/GenericCompositeFutureTest.java
new file mode 100644
index 000000000..39b75a421
--- /dev/null
+++ b/okapi-common/src/test/java/org/folio/okapi/common/GenericCompositeFutureTest.java
@@ -0,0 +1,103 @@
+package org.folio.okapi.common;
+
+import io.vertx.core.AsyncResult;
+import io.vertx.core.CompositeFuture;
+import io.vertx.core.Future;
+import io.vertx.core.Handler;
+import io.vertx.core.Promise;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.function.Function;
+import org.assertj.core.api.WithAssertions;
+import org.junit.Test;
+
+public class GenericCompositeFutureTest implements WithAssertions {
+  @Test
+  public void success() {
+    List<Future<String>> successSuccess = Arrays.asList(Future.succeededFuture(), Future.succeededFuture());
+    List<Future<String>> successFailure = Arrays.asList(Future.succeededFuture(), Future.failedFuture(""));
+    assertThat(GenericCompositeFuture.all(successSuccess).succeeded()).isTrue();
+    assertThat(GenericCompositeFuture.all(successFailure).failed()).isTrue();
+    assertThat(GenericCompositeFuture.any(successSuccess).succeeded()).isTrue();
+    assertThat(GenericCompositeFuture.any(successFailure).succeeded()).isTrue();
+    assertThat(GenericCompositeFuture.join(successSuccess).succeeded()).isTrue();
+    assertThat(GenericCompositeFuture.join(successFailure).failed()).isTrue();
+  }
+
+  @Test
+  public void completion() {
+    List<Future<Integer>> failureAndUnknown = Arrays.asList(Future.failedFuture(""), Promise.<Integer>promise().future());
+    assertThat(GenericCompositeFuture.all(failureAndUnknown).isComplete()).isTrue();
+    assertThat(GenericCompositeFuture.any(failureAndUnknown).isComplete()).isFalse();
+    assertThat(GenericCompositeFuture.join(failureAndUnknown).isComplete()).isFalse();
+  }
+
+  @Test
+  public void generics() {
+    List<MyFuture<Double>> list = Collections.emptyList();
+    CompositeFuture all = GenericCompositeFuture.all(list);
+    CompositeFuture any = GenericCompositeFuture.any(list);
+    CompositeFuture join = GenericCompositeFuture.join(list);
+    assertThat(all.succeeded()).isTrue();
+    assertThat(any.succeeded()).isTrue();
+    assertThat(join.succeeded()).isTrue();
+  }
+
+  class MyFuture<T> implements Future<T> {
+    @Override
+    public boolean isComplete() {
+      return false;
+    }
+
+    @Override
+    public Future<T> onComplete(Handler<AsyncResult<T>> handler) {
+      return null;
+    }
+
+    @Override
+    public T result() {
+      return null;
+    }
+
+    @Override
+    public Throwable cause() {
+      return null;
+    }
+
+    @Override
+    public boolean succeeded() {
+      return false;
+    }
+
+    @Override
+    public boolean failed() {
+      return false;
+    }
+
+    @Override
+    public <U> Future<U> compose(Function<T, Future<U>> successMapper, Function<Throwable, Future<U>> failureMapper) {
+      return null;
+    }
+
+    @Override
+    public <U> Future<U> map(Function<T, U> mapper) {
+      return null;
+    }
+
+    @Override
+    public <V> Future<V> map(V value) {
+      return null;
+    }
+
+    @Override
+    public Future<T> otherwise(Function<Throwable, T> mapper) {
+      return null;
+    }
+
+    @Override
+    public Future<T> otherwise(T value) {
+      return null;
+    }
+  };
+}