Add an item writer that will only write items satisfying a condition

src/batch/docs/domain/item-job/item-writer.md

@@ -11,6 +11,8 @@ It can be any class implementing [ItemWriterInterface](../../../src/Job/Item/Ite
   write items as a json string each on a line of a file.
 - [ChainWriter](../../../src/Job/Item/Writer/ChainWriter.php):
   write items on multiple item writers.
+- [ConditionalWriter](../../../src/Job/Item/Writer/ConditionalWriter.php):
+  will only write items that are matching your conditions.
 - [NullWriter](../../../src/Job/Item/Writer/NullWriter.php):
   do not write items.
 - [RoutingWriter](../../../src/Job/Item/Writer/RoutingWriter.php):

src/batch/src/Job/Item/Writer/ConditionalWriter.php

@@ -0,0 +1,70 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Yokai\Batch\Job\Item\Writer;
+
+use Yokai\Batch\Job\Item\ElementConfiguratorTrait;
+use Yokai\Batch\Job\Item\FlushableInterface;
+use Yokai\Batch\Job\Item\InitializableInterface;
+use Yokai\Batch\Job\Item\ItemWriterInterface;
+use Closure;
+use Yokai\Batch\Job\JobExecutionAwareInterface;
+use Yokai\Batch\Job\JobExecutionAwareTrait;
+
+/**
+ * This {@see ItemWriterInterface} will transfer writing
+ * to another {@see ItemWriterInterface},
+ * if the closure you provided tells to.
+ */
+final class ConditionalWriter implements
+    ItemWriterInterface,
+    JobExecutionAwareInterface,
+    InitializableInterface,
+    FlushableInterface
+{
+    use JobExecutionAwareTrait;
+    use ElementConfiguratorTrait;
+
+    private bool $initialized = false;
+
+    public function __construct(
+        private Closure $shouldWrite,
+        private ItemWriterInterface $writer,
+    ) {
+    }
+
+    public function write(iterable $items): void
+    {
+        $keptItems = [];
+        foreach ($items as $item) {
+            if (($this->shouldWrite)($item, $this->jobExecution)) {
+                $keptItems[] = $item;
+            }
+        }
+
+        if ($keptItems === []) {
+            return;
+        }
+
+        if (!$this->initialized) {
+            $this->configureElementJobContext($this->writer, $this->jobExecution);
+            $this->initializeElement($this->writer);
+            $this->initialized = true;
+        }
+
+        $this->writer->write($keptItems);
+    }
+
+    public function initialize(): void
+    {
+        $this->initialized = false;
+    }
+
+    public function flush(): void
+    {
+        if ($this->initialized) {
+            $this->flushElement($this->writer);
+        }
+    }
+}

src/batch/tests/Job/Item/Writer/ConditionalWriterTest.php

@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Yokai\Batch\Tests\Job\Item\Writer;
+
+use Yokai\Batch\Job\Item\Writer\ConditionalWriter;
+use PHPUnit\Framework\TestCase;
+use Yokai\Batch\JobExecution;
+use Yokai\Batch\Test\Job\Item\Writer\InMemoryWriter;
+use Yokai\Batch\Test\Job\Item\Writer\TestDebugWriter;
+
+class ConditionalWriterTest extends TestCase
+{
+    public function testWriteSomething(): void
+    {
+        $writer = new ConditionalWriter(
+            fn (int $number) => ($number % 2) === 0,
+            $debugWriter = new TestDebugWriter($memoryWriter = new InMemoryWriter())
+        );
+
+        $writer->setJobExecution(JobExecution::createRoot('123', 'test.conditional_writer'));
+        $writer->initialize();
+        $writer->write([1, 2, 3, 4, 5]);
+        $writer->write([6, 7, 8]);
+        $writer->flush();
+
+        $debugWriter->assertWasConfigured();
+        $debugWriter->assertWasUsed();
+        self::assertSame([[2, 4], [6, 8]], $memoryWriter->getBatchItems());
+    }
+
+    public function testWriteNothing(): void
+    {
+        $writer = new ConditionalWriter(
+            fn () => false,
+            $debugWriter = new TestDebugWriter($memoryWriter = new InMemoryWriter())
+        );
+
+        $writer->setJobExecution(JobExecution::createRoot('123', 'test.conditional_writer'));
+        $writer->initialize();
+        $writer->write([1, 2, 3, 4, 5]);
+        $writer->write([6, 7, 8]);
+        $writer->flush();
+
+        $debugWriter->assertWasNotConfigured();
+        $debugWriter->assertWasNotUsed();
+        self::assertSame([], $memoryWriter->getBatchItems());
+    }
+}