Throw specific exceptions on duplicate playheads

This will allow you to handle race conditions within your domain,
without having to bind it to a specific DBAL store.

src/Broadway/EventStore/DBALEventStore.php

@@ -15,6 +15,7 @@
 use Broadway\Domain\DomainEventStream;
 use Broadway\Domain\DomainEventStreamInterface;
 use Broadway\Domain\DomainMessage;
+use Broadway\EventStore\Exception\DuplicatePlayheadException;
 use Broadway\EventStore\Exception\InvalidIdentifierException;
 use Broadway\EventStore\Management\Criteria;
 use Broadway\EventStore\Management\CriteriaNotSupportedException;
@@ -23,6 +24,7 @@
 use Broadway\UuidGenerator\Converter\BinaryUuidConverterInterface;
 use Doctrine\DBAL\Connection;
 use Doctrine\DBAL\DBALException;
+use Doctrine\DBAL\Exception\UniqueConstraintViolationException;
 use Doctrine\DBAL\Schema\Schema;
 use Doctrine\DBAL\Version;
 
@@ -115,6 +117,10 @@ public function append($id, DomainEventStreamInterface $eventStream)
             }
 
             $this->connection->commit();
+        } catch (UniqueConstraintViolationException $exception) {
+            $this->connection->rollBack();
+
+            throw DuplicatePlayheadException::create($exception);
         } catch (DBALException $exception) {
             $this->connection->rollBack();
 

src/Broadway/EventStore/EventStoreInterface.php

@@ -12,6 +12,7 @@
 namespace Broadway\EventStore;
 
 use Broadway\Domain\DomainEventStreamInterface;
+use Broadway\EventStore\Exception\DuplicatePlayheadException;
 
 /**
  * Loads and stores events.
@@ -28,6 +29,8 @@ public function load($id);
     /**
      * @param mixed                      $id
      * @param DomainEventStreamInterface $eventStream
+     *
+     * @throws DuplicatePlayheadException
      */
     public function append($id, DomainEventStreamInterface $eventStream);
 }

src/Broadway/EventStore/Exception/DuplicatePlayheadException.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Broadway\EventStore\Exception;
+
+use Broadway\EventStore\EventStoreException;
+use Exception;
+
+class DuplicatePlayheadException extends EventStoreException
+{
+    public static function create(Exception $exception)
+    {
+        return new self(null, 0, $exception);
+    }
+}

src/Broadway/EventStore/InMemoryEventStore.php

@@ -13,6 +13,7 @@
 
 use Broadway\Domain\DomainEventStream;
 use Broadway\Domain\DomainEventStreamInterface;
+use Broadway\EventStore\Exception\DuplicatePlayheadException;
 use Broadway\EventStore\Management\Criteria;
 use Broadway\EventStore\Management\EventStoreManagementInterface;
 
@@ -61,7 +62,7 @@ public function append($id, DomainEventStreamInterface $eventStream)
     private function assertPlayhead($events, $playhead)
     {
         if (isset($events[$playhead])) {
-            throw new InMemoryEventStoreException(
+            throw new DuplicatePlayheadException(
                 sprintf("An event with playhead '%d' is already committed.", $playhead)
             );
         }

test/Broadway/EventStore/EventStoreTest.php

@@ -87,7 +87,7 @@ public function it_throws_an_exception_when_requesting_the_stream_of_a_non_exist
     /**
      * @test
      * @dataProvider idDataProvider
-     * @expectedException \Broadway\EventStore\EventStoreException
+     * @expectedException Broadway\EventStore\Exception\DuplicatePlayheadException
      */
     public function it_throws_an_exception_when_appending_a_duplicate_playhead($id)
     {