refactor projection & query api

Author: DavidBadura

src/DCB/CompositeProjection.php

@@ -5,15 +5,9 @@
 namespace Patchlevel\EventSourcing\DCB;
 
 use Patchlevel\EventSourcing\Message\Message;
-use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+use Patchlevel\EventSourcing\Store\Query;
 
-use function array_diff;
 use function array_map;
-use function array_merge;
-use function array_unique;
-use function array_values;
-use function in_array;
-use function sort;
 
 /**
  * @experimental
@@ -27,36 +21,15 @@ public function __construct(
     ) {
     }
 
-    /** @return list<string> */
-    public function tagFilter(): array
+    public function query(): Query
     {
-        $tags = [];
+        $query = new Query();
 
         foreach ($this->projections as $projection) {
-            $tags = array_merge($tags, $projection->tagFilter());
+            $query = $query->add($projection->queryComponent());
         }
 
-        return array_values(array_unique($tags));
-    }
-
-    /** @return list<list<string>> */
-    public function groupedTagFilter(): array
-    {
-        $result = [];
-
-        foreach ($this->projections as $projection) {
-            $tags = $projection->tagFilter();
-
-            sort($tags);
-
-            if (in_array($tags, $result, true)) {
-                continue;
-            }
-
-            $result[] = $tags;
-        }
-
-        return $result;
+        return $query;
     }
 
     /** @return array<string, mixed> */
@@ -69,12 +42,8 @@ public function initialState(): array
 
     public function apply(mixed $state, Message $message): mixed
     {
-        $tags = $message->header(TagsHeader::class)->tags;
-
         foreach ($this->projections as $name => $projection) {
-            $neededTags = $projection->tagFilter();
-
-            if (!$this->isSubset($neededTags, $tags)) {
+            if (!$projection->queryComponent()->match($message)) {
                 continue;
             }
 
@@ -83,13 +52,4 @@ public function apply(mixed $state, Message $message): mixed
 
         return $state;
     }
-
-    /**
-     * @param list<string> $needle
-     * @param list<string> $haystack
-     */
-    private function isSubset(array $needle, array $haystack): bool
-    {
-        return empty(array_diff($needle, $haystack));
-    }
 }

src/DCB/Projection.php

@@ -7,6 +7,7 @@
 use Closure;
 use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\QueryComponent;
 use ReflectionClass;
 use RuntimeException;
 
@@ -26,6 +27,11 @@ abstract public function tagFilter(): array;
     /** @return S */
     abstract public function initialState(): mixed;
 
+    public function queryComponent(): QueryComponent
+    {
+        return new QueryComponent($this->tagFilter());
+    }
+
     /**
      * @param S $state
      *

src/DCB/ProjectionBuilder.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+/** @experimental */
+interface ProjectionBuilder
+{
+    /**
+     * @param array<string, Projection> $projections
+     *
+     * @return array<string, mixed>
+     */
+    public function build(
+        array $projections,
+    ): array;
+}

src/DCB/StoreDecisionModelBuilder.php

@@ -6,10 +6,6 @@
 
 use Patchlevel\EventSourcing\Store\AppendCondition;
 use Patchlevel\EventSourcing\Store\AppendStore;
-use Patchlevel\EventSourcing\Store\Query;
-use Patchlevel\EventSourcing\Store\QueryComponent;
-
-use function array_map;
 
 /** @experimental */
 final class StoreDecisionModelBuilder implements DecisionModelBuilder
@@ -25,11 +21,7 @@ public function build(
     ): DecisionModel {
         $projection = new CompositeProjection($projections);
 
-        $query = new Query(...array_map(
-            static fn (array $tags) => new QueryComponent($tags),
-            $projection->groupedTagFilter(),
-        ));
-
+        $query = $projection->query();
         $stream = $this->store->query($query);
 
         $state = $projection->initialState();

src/DCB/StoreProjectionBuilder.php

@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+use Patchlevel\EventSourcing\Store\AppendStore;
+
+/** @experimental */
+final class StoreProjectionBuilder implements ProjectionBuilder
+{
+    public function __construct(
+        private AppendStore $store,
+    ) {
+    }
+
+    /**
+     * @param array<string, Projection> $projections
+     *
+     * @return array<string, mixed>
+     */
+    public function build(
+        array $projections,
+    ): array {
+        $projection = new CompositeProjection($projections);
+
+        $query = $projection->query();
+        $stream = $this->store->query($query);
+
+        $state = $projection->initialState();
+
+        foreach ($stream as $message) {
+            $state = $projection->apply($state, $message);
+        }
+
+        return $state;
+    }
+}

src/Store/Query.php

@@ -14,4 +14,17 @@ public function __construct(
     ) {
         $this->components = $components;
     }
+
+    public function add(QueryComponent $component): self
+    {
+        foreach ($this->components as $c) {
+            if ($c->equals($component)) {
+                return $this;
+            }
+        }
+
+        $components = [...$this->components, $component];
+
+        return new self(...$components);
+    }
 }

src/Store/QueryComponent.php

@@ -4,11 +4,45 @@
 
 namespace Patchlevel\EventSourcing\Store;
 
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+
+use function array_diff;
+use function sort;
+
 final class QueryComponent
 {
     /** @param list<string> $tags */
     public function __construct(
         public readonly array $tags,
     ) {
+        sort($tags);
+    }
+
+    public function match(Message $message): bool
+    {
+        if ($this->tags === []) {
+            return true;
+        }
+
+        if (!$message->hasHeader(TagsHeader::class)) {
+            return false;
+        }
+
+        return $this->isSubset($this->tags, $message->header(TagsHeader::class)->tags);
+    }
+
+    public function equals(self $queryComponent): bool
+    {
+        return $this->tags === $queryComponent->tags;
+    }
+
+    /**
+     * @param list<string> $needle
+     * @param list<string> $haystack
+     */
+    private function isSubset(array $needle, array $haystack): bool
+    {
+        return empty(array_diff($needle, $haystack));
     }
 }