[Fix #1343] Add ForkTask shortcut to DSL (#1344)

Signed-off-by: fjtirado <ftirados@redhat.com>

Author: fjtirado

experimental/fluent/func/src/main/java/io/serverlessworkflow/fluent/func/dsl/FuncDSL.java

@@ -1116,6 +1116,32 @@ public static <T> FuncTaskConfigurer forEach(
     return list -> list.forEach(j -> j.collection(ctx -> collection).tasks(body));
   }
 
+  /**
+   * This is helper to quickly build fork task where every branch is unnamed and consist of just one
+   * task. For more advanced use cases, please check FuncTaskItemListBuilder.fork
+   *
+   * @param name the name of the fork task
+   * @param branches every task in this input array will become a branch of the fork.
+   * @return FuncTaskConfigurer
+   */
+  public static FuncTaskConfigurer fork(String name, FuncTaskConfigurer... branches) {
+    if (branches == null || branches.length == 0) {
+      throw new IllegalArgumentException("branches must not be null or empty");
+    }
+    return list ->
+        list.fork(
+            name,
+            forkBuilder -> {
+              for (FuncTaskConfigurer branch : branches) {
+                forkBuilder.branch((FuncTaskItemListBuilder v) -> branch.accept(v));
+              }
+            });
+  }
+
+  public static FuncTaskConfigurer fork(FuncTaskConfigurer... branches) {
+    return fork(null, branches);
+  }
+
   /**
    * Set a raw expression on the current list (advanced).
    *

experimental/test/src/test/java/io/serverlessworkflow/fluent/test/ForkFuncTest.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2020-Present The Serverless Workflow Specification Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.serverlessworkflow.fluent.test;
+
+import static io.serverlessworkflow.fluent.func.dsl.FuncDSL.*;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import io.serverlessworkflow.api.types.Workflow;
+import io.serverlessworkflow.fluent.func.FuncWorkflowBuilder;
+import io.serverlessworkflow.impl.WorkflowApplication;
+import org.junit.jupiter.api.Test;
+
+public class ForkFuncTest {
+
+  @Test
+  void testForkVerbose() {
+    testIt(
+        FuncWorkflowBuilder.workflow("parallel-execution-workflow")
+            .tasks(
+                funcTaskItemListBuilder ->
+                    funcTaskItemListBuilder.fork(
+                        funcForkTaskBuilder ->
+                            funcForkTaskBuilder.branches(
+                                inner -> {
+                                  inner.function(f -> f.function(this::doubleIt, int.class));
+                                  inner.function(f -> f.function(this::halfIt, int.class));
+                                })))
+            .build());
+  }
+
+  @Test
+  void testForkSyntaxSugar() {
+    testIt(
+        FuncWorkflowBuilder.workflow("parallel-execution-workflow")
+            .tasks(fork(function(this::doubleIt), function(this::halfIt)))
+            .build());
+  }
+
+  private void testIt(Workflow workflow) {
+    try (WorkflowApplication app = WorkflowApplication.builder().build()) {
+      assertThat(
+              app.workflowDefinition(workflow).instance(8).start().join().asCollection().stream()
+                  .flatMap(m -> m.asMap().orElseThrow().values().stream())
+                  .toList())
+          .containsExactlyInAnyOrder(4, 16);
+    }
+  }
+
+  private int doubleIt(int number) {
+    return number << 1;
+  }
+
+  private int halfIt(int number) {
+    return number >> 1;
+  }
+}