Add sorting command

src/Model/Command/Sorting.php

@@ -0,0 +1,42 @@
+<?php declare(strict_types=1);
+
+namespace Lmc\Matej\Model\Command;
+
+/**
+ * Sorting items is a way how to use Matej to deliver personalized experience to users.
+ * It allows to sort given list of items according to the user preference.
+ */
+class Sorting extends AbstractCommand
+{
+    /** @var string */
+    private $userId;
+    /** @var string[] */
+    private $itemIds = [];
+
+    private function __construct(string $userId, array $itemIds)
+    {
+        $this->userId = $userId;
+        $this->itemIds = $itemIds;
+    }
+
+    /**
+     * Sort given item ids for user-based recommendations.
+     */
+    public static function create(string $userId, array $itemIds): self
+    {
+        return new static($userId, $itemIds);
+    }
+
+    public function getCommandType(): string
+    {
+        return 'sorting';
+    }
+
+    public function getCommandParameters(): array
+    {
+        return [
+            'user_id' => $this->userId,
+            'item_ids' => $this->itemIds,
+        ];
+    }
+}

tests/Model/Command/SortingTest.php

@@ -0,0 +1,37 @@
+<?php declare(strict_types=1);
+
+namespace Lmc\Matej\Model\Command;
+
+use Lmc\Matej\TestCase;
+
+class SortingTest extends TestCase
+{
+    /** @test */
+    public function shouldBeInstantiableViaNamedConstructor(): void
+    {
+        $userId = 'user-id';
+        $itemIds = ['item-1', 'item-3', 'item-2'];
+
+        $command = Sorting::create($userId, $itemIds);
+        $this->assertSortingObject($command, $userId, $itemIds);
+    }
+
+    /**
+     * Execute asserts against user merge object
+     * @param object $object
+     */
+    private function assertSortingObject($object, string $userId, array $itemIds): void
+    {
+        $this->assertInstanceOf(Sorting::class, $object);
+        $this->assertSame(
+            [
+                'type' => 'sorting',
+                'parameters' => [
+                    'user_id' => $userId,
+                    'item_ids' => $itemIds,
+                ],
+            ],
+            $object->jsonSerialize()
+        );
+    }
+}