Add support callback sort

src/AllowedSort.php

@@ -5,6 +5,7 @@
 use Spatie\QueryBuilder\Enums\SortDirection;
 use Spatie\QueryBuilder\Exceptions\InvalidDirection;
 use Spatie\QueryBuilder\Sorts\Sort;
+use Spatie\QueryBuilder\Sorts\SortsCallback;
 use Spatie\QueryBuilder\Sorts\SortsField;
 
 class AllowedSort
@@ -54,6 +55,11 @@ public static function custom(string $name, Sort $sortClass, ?string $internalNa
         return new static($name, $sortClass, $internalName);
     }
 
+    public static function callback(string $name, $callback, ?string $internalName = null): self
+    {
+        return new static($name, new SortsCallback($callback), $internalName);
+    }
+
     public function getName(): string
     {
         return $this->name;

src/Sorts/SortsCallback.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace Spatie\QueryBuilder\Sorts;
+
+use Illuminate\Database\Eloquent\Builder;
+
+class SortsCallback implements Sort
+{
+    /**
+     * @var callable a PHP callback of the following signature:
+     * `function (\Illuminate\Database\Eloquent\Builder $builder, bool $descending, string $property)`
+     */
+    private $callback;
+
+    public function __construct($callback)
+    {
+        $this->callback = $callback;
+    }
+
+    /** {@inheritdoc} */
+    public function __invoke(Builder $query, bool $descending, string $property)
+    {
+        return call_user_func($this->callback, $query, $descending, $property);
+    }
+}

tests/SortsCallbackTest.php

@@ -0,0 +1,77 @@
+<?php
+
+namespace Spatie\QueryBuilder\Tests;
+
+use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Support\Facades\DB;
+use Spatie\QueryBuilder\AllowedSort;
+use Spatie\QueryBuilder\QueryBuilder;
+use Spatie\QueryBuilder\Tests\Concerns\AssertsCollectionSorting;
+use Spatie\QueryBuilder\Tests\TestClasses\Models\TestModel;
+use Illuminate\Http\Request;
+
+class SortsCallbackTest extends TestCase
+{
+    use AssertsCollectionSorting;
+
+    /** @var \Illuminate\Support\Collection */
+    protected $models;
+
+    public function setUp(): void
+    {
+        parent::setUp();
+
+        DB::enableQueryLog();
+
+        $this->models = factory(TestModel::class, 5)->create();
+    }
+
+    /** @test */
+    public function it_should_sort_by_closure()
+    {
+        $sortedModels = $this
+            ->createQueryFromSortRequest('callback')
+            ->allowedSorts(AllowedSort::callback('callback', function (Builder $query, $descending) {
+                $query->orderBy('name', $descending ? 'DESC' : 'ASC');
+            }))
+            ->get();
+
+        $this->assertQueryExecuted('select * from `test_models` order by `name` asc');
+        $this->assertSortedAscending($sortedModels, 'name');
+    }
+
+    /** @test */
+    public function it_should_sort_by_array_callback()
+    {
+        $sortedModels = $this
+            ->createQueryFromSortRequest('callback')
+            ->allowedSorts(AllowedSort::callback('callback', [$this, 'sortCallback']))
+            ->get();
+
+        $this->assertQueryExecuted('select * from `test_models` order by `name` asc');
+        $this->assertSortedAscending($sortedModels, 'name');
+    }
+
+    public function sortCallback(Builder $query, $descending)
+    {
+        $query->orderBy('name', $descending ? 'DESC' : 'ASC');
+    }
+
+    protected function createQueryFromSortRequest(string $sort): QueryBuilder
+    {
+        $request = new Request([
+            'sort' => $sort,
+        ]);
+
+        return QueryBuilder::for(TestModel::class, $request);
+    }
+
+    protected function assertQueryExecuted(string $query)
+    {
+        $queries = array_map(function ($queryLogItem) {
+            return $queryLogItem['query'];
+        }, DB::getQueryLog());
+
+        $this->assertContains($query, $queries);
+    }
+}