Feat: Multiple next tick callbacks (#29)

Author: bpolaszek

Diff for: src/EtlExecutor.php

@@ -110,11 +110,10 @@ public function process(mixed $source = null, mixed $destination = null, array $
 
     private function consumeNextTick(EtlState $state): void
     {
-        if (null === $state->nextTickCallback) {
-            return;
+        foreach ($state->nextTickCallbacks as $callback) {
+            ($callback)($state);
+            $state->nextTickCallbacks->detach($callback);
         }
-
-        ($state->nextTickCallback)($state);
     }
 
     /**

Diff for: src/EtlState.php

@@ -9,15 +9,18 @@
 use BenTools\ETL\Internal\ClonableTrait;
 use Closure;
 use DateTimeImmutable;
+use SplObjectStorage;
 
 final class EtlState
 {
     use ClonableTrait;
 
     /**
      * @internal
+     *
+     * @var SplObjectStorage<Closure, Closure>
      */
-    public ?Closure $nextTickCallback = null;
+    public SplObjectStorage $nextTickCallbacks;
 
     private int $nbLoadedItemsSinceLastFlush = 0;
     private bool $earlyFlush = false;
@@ -39,20 +42,12 @@ public function __construct(
         public readonly ?DateTimeImmutable $endedAt = null,
         public readonly mixed $output = null,
     ) {
+        $this->nextTickCallbacks ??= new SplObjectStorage();
     }
 
-    public function nextTick(?callable $callback): void
+    public function nextTick(callable $callback): void
     {
-        if (null === $callback) {
-            $this->nextTickCallback = null;
-
-            return;
-        }
-
-        $this->nextTickCallback = static function (EtlState $state) use ($callback) {
-            $callback($state);
-            $state->nextTick(null);
-        };
+        $this->nextTickCallbacks->attach(static fn (EtlState $state) => $callback($state));
     }
 
     /**

Diff for: tests/Behavior/NextTickTest.php

@@ -4,10 +4,12 @@
 
 namespace BenTools\ETL\Tests\Behavior;
 
+use ArrayObject;
 use BenTools\ETL\EtlConfiguration;
 use BenTools\ETL\EtlExecutor;
 use BenTools\ETL\EtlState;
 use BenTools\ETL\EventDispatcher\Event\ExtractEvent;
+use BenTools\ETL\EventDispatcher\Event\LoadEvent;
 use BenTools\ETL\Tests\InMemoryLoader;
 
 use function expect;
@@ -35,3 +37,21 @@
         ->and($report->output[0])->toBe(['banana', 'apple'])
         ->and($report->output[1])->toBe(['strawberry', 'raspberry', 'peach']);
 });
+
+it('can trigger several callbacks, which are called only once', function () {
+    // Given
+    $bucket = new ArrayObject();
+    $etl = (new EtlExecutor())
+        ->onLoad(function (LoadEvent $event) use ($bucket) {
+            if ('apple' === $event->item) {
+                $event->state->nextTick(fn (EtlState $state) => $bucket->append('apple'));
+                $event->state->nextTick(fn (EtlState $state) => $bucket->append('APPLE'));
+            }
+        });
+
+    // When
+    $report = $etl->process(['banana', 'apple', 'strawberry', 'raspberry', 'peach']);
+
+    // Then
+    expect([...$bucket])->toBe(['apple', 'APPLE']);
+});