Merge pull request #103 from OwlyCode/promise-paginator

Added promise handling on Paginator

Author: mcg-web

Relay/Connection/Paginator.php

@@ -11,23 +11,34 @@
 
 namespace Overblog\GraphQLBundle\Relay\Connection;
 
+use GraphQL\Executor\Promise\Promise;
 use Overblog\GraphQLBundle\Definition\Argument;
 use Overblog\GraphQLBundle\Relay\Connection\Output\Connection;
 use Overblog\GraphQLBundle\Relay\Connection\Output\ConnectionBuilder;
 
 class Paginator
 {
+    const MODE_REGULAR = false;
+    const MODE_PROMISE = true;
+
     /**
      * @var callable
      */
     private $fetcher;
 
+    /**
+     * @var bool
+     */
+    private $promise;
+
     /**
      * @param callable $fetcher
+     * @param bool     $promise
      */
-    public function __construct(callable $fetcher)
+    public function __construct(callable $fetcher, $promise = self::MODE_REGULAR)
     {
         $this->fetcher = $fetcher;
+        $this->promise = $promise;
     }
 
     /**
@@ -47,10 +58,12 @@ public function backward($args, $total, array $callableArgs = [])
 
         $entities = call_user_func($this->fetcher, $offset, $limit);
 
-        return ConnectionBuilder::connectionFromArraySlice($entities, $args, [
-            'sliceStart' => $offset,
-            'arrayLength' => $total,
-        ]);
+        return $this->handleEntities($entities, function ($entities) use ($args, $offset, $total) {
+            return ConnectionBuilder::connectionFromArraySlice($entities, $args, [
+                'sliceStart' => $offset,
+                'arrayLength' => $total,
+            ]);
+        });
     }
 
     /**
@@ -68,14 +81,18 @@ public function forward($args)
         if (!is_numeric(ConnectionBuilder::cursorToOffset($args['after'])) || !$args['after']) {
             $entities = call_user_func($this->fetcher, $offset, $limit + 1);
 
-            return ConnectionBuilder::connectionFromArray($entities, $args);
+            return $this->handleEntities($entities, function ($entities) use ($args) {
+                return ConnectionBuilder::connectionFromArray($entities, $args);
+            });
         } else {
             $entities = call_user_func($this->fetcher, $offset, $limit + 2);
 
-            return ConnectionBuilder::connectionFromArraySlice($entities, $args, [
-                'sliceStart' => $offset,
-                'arrayLength' => $offset + count($entities),
-            ]);
+            return $this->handleEntities($entities, function ($entities) use ($args, $offset) {
+                return ConnectionBuilder::connectionFromArraySlice($entities, $args, [
+                    'sliceStart' => $offset,
+                    'arrayLength' => $offset + count($entities),
+                ]);
+            });
         }
     }
 
@@ -97,6 +114,21 @@ public function auto($args, $total, $callableArgs = [])
         }
     }
 
+    /**
+     * @param array|object $entities An array of entities to paginate or a promise
+     * @param callable     $callback
+     *
+     * @return Connection|object A connection or a promise
+     */
+    private function handleEntities($entities, callable $callback)
+    {
+        if ($this->promise) {
+            return $entities->then($callback);
+        }
+
+        return call_user_func($callback, $entities);
+    }
+
     /**
      * @param Argument|array $args
      *

Resources/doc/helpers/relay-paginator.md

@@ -16,20 +16,20 @@ This method can be used to get a slice of a data set by passing:
 - the args, as a `ConnectionArguments` object
 - the meta, as a `ArraySliceMetaInfo` object
 
-The sliced data set must contains: 
+The sliced data set must contains:
 
 - the item before the first item you want
 - the item after the slice, so `PageInfo->hasNextPage` can be calculated
- 
-Exemple:
- 
+
+Example:
+
 - full data set is `['A','B','C','D','E']`
 - we want 2 items after `A`, meaning `['B','C']`
 
 
 - `after` cursor will be `arrayconnection:0`
 - `offset` will be calculated to `0`
-- so we need to passed a sliced data with `['A','B','C','D']` to `connectionFromArraySlice()` 
+- so we need to passed a sliced data with `['A','B','C','D']` to `connectionFromArraySlice()`
 
 ## Paginator
 
@@ -39,8 +39,8 @@ The purpose if this helper is to provide an easy way to paginate in a data set p
 
 When constructing the paginator, you need to pass a callable which will be responsible for providing the sliced data set.
 
-### Exemple
- 
+### Example
+
 #### With a `first` Relay parameter
 
 ```php
@@ -120,7 +120,7 @@ $paginator = new Paginator(function ($offset, $limit) {
 $result = $paginator->forward(
     new Argument(
         [
-            'first' => 1, 
+            'first' => 1,
             'after' => base64_encode('arrayconnection:2')
         ]
     )
@@ -145,7 +145,7 @@ array(1) {
 ```
 
 **Important note:**
- 
+
 The callback function will receive:
 
 - `$offset = 2`
@@ -194,3 +194,21 @@ $result = $paginator->backward(
 ```
 
 You should get the 4 last items of the _data set_.
+
+#### Promise handling
+
+Paginator also supports promises if you [use that feature](https://github.com/webonyx/graphql-php/pull/67)
+with the bundle. All you have to do is to toggle the `MODE_PROMISE` flag on and
+update your callback to return a `Executor/Promise/Promise` instance.
+
+```php
+// Let's pretend we use dataloader ( https://github.com/overblog/dataloader-php )
+public function resolveList($args)
+{
+    $pagination = new Paginator(function ($offset, $limit) {
+        return $this->dataLoader->loadMany($this->elasticsearch->getIds($offset, $limit));
+    }, Paginator::MODE_PROMISE); // This flag indicates that we will return a promise instead of an array of instances
+
+    return $pagination->forward($args);
+}
+```

Tests/Relay/Connection/PaginatorTest.php

@@ -282,4 +282,23 @@ public function testTotalCallableWithArguments()
         $this->assertSameEdgeNodeValue(['B', 'C', 'D', 'E'], $result);
         $this->assertTrue($result->pageInfo->hasPreviousPage);
     }
+
+    public function testPromiseMode()
+    {
+        $promise = $this->getMockBuilder('GraphQL\Executor\Promise\Promise')
+            ->setMethods(['then'])
+            ->getMock()
+        ;
+
+        $promise->expects($this->once())->method('then');
+
+        $paginator = new Paginator(function ($offset, $limit) use ($promise) {
+            $this->assertSame(0, $offset);
+            $this->assertSame(5, $limit);
+
+            return $promise;
+        }, Paginator::MODE_PROMISE);
+
+        $result = $paginator->auto(new Argument(['first' => 4]), 5);
+    }
 }