Add support for cursor pagination

This commit adds support for Laravel cursor pagination.
Fixes #2314

Author: Jeroenwv

src/Eloquent/Builder.php

@@ -216,4 +216,35 @@ public function getConnection()
     {
         return $this->query->getConnection();
     }
+
+    /**
+     * @inheritdoc
+     */
+    protected function ensureOrderForCursorPagination($shouldReverse = false)
+    {
+        if (empty($this->query->orders)) {
+            $this->enforceOrderBy();
+        }
+
+        if ($shouldReverse) {
+            $this->query->orders = collect($this->query->orders)->map(function ($direction) {
+                return $direction === 1 ? -1 : 1;
+            })->toArray();
+        }
+
+        return $this->mapMongodbOrdersToEloquentOrders($this->query->orders);
+    }
+
+    private function mapMongodbOrdersToEloquentOrders($orders) {
+        $eloquentOrders = [];
+
+        foreach($orders as $column => $direction) {
+            $eloquentOrders[] = [
+                'column' => $column,
+                'direction' => $direction === 1 ? 'asc' : 'desc',
+            ];
+        }
+
+        return collect($eloquentOrders);
+    }
 }

tests/QueryTest.php

@@ -383,6 +383,29 @@ public function testPaginate(): void
         $this->assertEquals(1, $results->currentPage());
     }
 
+    public function testCursorPaginate(): void
+    {
+        $results = User::cursorPaginate(2);
+        $this->assertEquals(2, $results->count());
+        $this->assertNotNull($results->first()->title);
+        $this->assertNotNull($results->nextCursor());
+        $this->assertTrue($results->onFirstPage());
+
+        $results = User::cursorPaginate(2, ['name', 'age']);
+        $this->assertEquals(2, $results->count());
+        $this->assertNull($results->first()->title);
+
+        $results = User::orderBy('age', 'desc')->cursorPaginate(2, ['name', 'age']);
+        $this->assertEquals(2, $results->count());
+        $this->assertEquals(37, $results->first()->age);
+        $this->assertNull($results->first()->title);
+
+        $results = User::whereNotNull('age')->orderBy('age', 'asc')->cursorPaginate(2, ['name', 'age']);
+        $this->assertEquals(2, $results->count());
+        $this->assertEquals(13, $results->first()->age);
+        $this->assertNull($results->first()->title);
+    }
+
     public function testUpdate(): void
     {
         $this->assertEquals(1, User::where(['name' => 'John Doe'])->update(['name' => 'Jim Morrison']));