Added support for multipart stream created from uri streams (#27)

* Added support for multipart uri streams by ensuring content from non-seekable streams is not fetched using string casting.
Added testSupportURIResources phpUnit test validating the multipart stream created from an uri resource.
Changed composer dev requirement zendframework/zend-diactoros for guzzlehttp/psr7 due to the fact that zend-diactoros DiactorosStreamFactory's createStream function runs a rewind which throws an exception if stream is not seekable.
Removed dependency on Zend\Diactoros\Stream in unit tests.

* Reverted to Diactoros dependency.

* refactoring: improved naming in line with other tests.

* when building the stream changed from toString via string casting to explicitly calling __toString() for clarity as suggested by @Nyholm

Author: Mats

src/MultipartStreamBuilder.php

@@ -95,7 +95,14 @@ public function build()
                 $this->getHeaders($data['headers'])."\r\n";
 
             // Convert the stream to string
-            $streams .= (string) $data['contents'];
+            /* @var $contentStream StreamInterface */
+            $contentStream = $data['contents'];
+            if ($contentStream->isSeekable()) {
+                $streams .= $contentStream->__toString();
+            } else {
+                $streams .= $contentStream->getContents();
+            }
+
             $streams .= "\r\n";
         }
 

tests/FunctionTest.php

@@ -33,6 +33,22 @@ public function testSupportResources()
         $this->assertTrue(false !== strpos($multipartStream, 'Content-Type: image/png'));
     }
 
+    public function testSupportURIResources()
+    {
+        $url = 'https://raw.githubusercontent.com/php-http/multipart-stream-builder/master/tests/Resources/httplug.png';
+        $resource = fopen($url, 'r');
+
+        $builder = new MultipartStreamBuilder();
+        $builder->addResource('image', $resource);
+        $multipartStream = (string) $builder->build();
+
+        $this->assertTrue(false !== strpos($multipartStream, 'Content-Disposition: form-data; name="image"; filename="httplug.png"'));
+        $this->assertTrue(false !== strpos($multipartStream, 'Content-Type: image/png'));
+
+        $urlContents = file_get_contents($url);
+        $this->assertContains($urlContents, $multipartStream);
+    }
+
     public function testResourceFilenameIsNotLocaleAware()
     {
         // Get current locale