[RFC] Lazy adapters implementation

src/Pagerfanta/Adapter/ElasticaAdapter.php

@@ -14,7 +14,7 @@
 use Elastica\Query;
 use Elastica\SearchableInterface;
 
-class ElasticaAdapter implements AdapterInterface
+class ElasticaAdapter implements LazyAdapterInterface
 {
     /**
      * @var Query

src/Pagerfanta/Adapter/LazyAdapterInterface.php

@@ -0,0 +1,22 @@
+<?php
+
+/*
+ * This file is part of the Pagerfanta package.
+ *
+ * (c) Pablo Díez <pablodip@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Pagerfanta\Adapter;
+
+/**
+ * LazyAdapterInterface that marks adapter lazy.
+ *
+ * @author Konstantin Myakshin <koc-dp@yandex.ru>
+ */
+interface LazyAdapterInterface extends AdapterInterface
+{
+
+}

src/Pagerfanta/Pagerfanta.php

@@ -13,6 +13,7 @@
 
 use OutOfBoundsException;
 use Pagerfanta\Adapter\AdapterInterface;
+use Pagerfanta\Adapter\LazyAdapterInterface;
 use Pagerfanta\Exception\LogicException;
 use Pagerfanta\Exception\NotBooleanException;
 use Pagerfanta\Exception\NotIntegerException;
@@ -227,7 +228,9 @@ private function filterCurrentPage($currentPage)
     {
         $currentPage = $this->toInteger($currentPage);
         $this->checkCurrentPage($currentPage);
-        $currentPage = $this->filterOutOfRangeCurrentPage($currentPage);
+        if (!$this->adapter instanceof LazyAdapterInterface) {
+            $currentPage = $this->filterOutOfRangeCurrentPage($currentPage);
+        }
 
         return $currentPage;
     }
@@ -318,7 +321,18 @@ private function getCurrentPageResultsFromAdapter()
         $offset = $this->calculateOffsetForCurrentPageResults();
         $length = $this->getMaxPerPage();
 
-        return $this->adapter->getSlice($offset, $length);
+        $slice = $this->adapter->getSlice($offset, $length);
+
+        if ($this->adapter instanceof LazyAdapterInterface) {
+            $page = $this->filterOutOfRangeCurrentPage($this->getCurrentPage());
+            if ($page != $this->getCurrentPage()) {
+                $this->setCurrentPage($page);
+
+                return $this->getCurrentPageResultsFromAdapter();
+            }
+        }
+
+        return $slice;
     }
 
     private function calculateOffsetForCurrentPageResults()

tests/Pagerfanta/Tests/PagerfantaTest.php

@@ -672,6 +672,42 @@ public function testPagerfantaShouldImplementIteratorAggregateInterface()
         $this->assertInstanceOf('IteratorAggregate', $this->pagerfanta);
     }
 
+    public function testLazyAdapterDoNotCallsGetNbResultsOnSetCurrentPage()
+    {
+        $adapter = $this->getMock('Pagerfanta\Adapter\LazyAdapterInterface');
+
+        $adapter
+            ->expects($this->never())
+            ->method('getNbResults');
+
+        $pagerfanta = new Pagerfanta($adapter);
+        $pagerfanta->setMaxPerPage(10);
+        $pagerfanta->setCurrentPage(3);
+    }
+
+    /**
+     * @expectedException Pagerfanta\Exception\OutOfRangeCurrentPageException
+     */
+    public function testLazyAdapterCallsGetNbResultsOnGetCurrentPageResults()
+    {
+        $adapter = $this->getMock('Pagerfanta\Adapter\LazyAdapterInterface');
+
+        $adapter
+            ->expects($this->any())
+            ->method('getSlice')
+            ->will($this->returnValue(range(0, 9)));
+
+        $adapter
+            ->expects($this->any())
+            ->method('getNbResults')
+            ->will($this->returnValue(20));
+
+        $pagerfanta = new Pagerfanta($adapter);
+        $pagerfanta->setMaxPerPage(10);
+        $pagerfanta->setCurrentPage(3);
+        $pagerfanta->getCurrentPageResults();
+    }
+
     private function assertResetCurrentPageResults($callback)
     {
         $this->setAdapterNbResultsAny(100);