From 6806ba94e0371b7f6ec5a4e7f2cf8b0820dec17d Mon Sep 17 00:00:00 2001
From: Stephan Unverwerth <s.unverwerth@gmx.de>
Date: Tue, 25 Oct 2016 23:50:36 +0200
Subject: [PATCH] Async ProtocolStreamWriter (#112)

---
 src/ProtocolStreamWriter.php       | 74 ++++++++++++++++++++++++------
 tests/ProtocolStreamWriterTest.php | 10 +++-
 2 files changed, 68 insertions(+), 16 deletions(-)

diff --git a/src/ProtocolStreamWriter.php b/src/ProtocolStreamWriter.php
index 2ac3579..41d7afc 100644
--- a/src/ProtocolStreamWriter.php
+++ b/src/ProtocolStreamWriter.php
@@ -4,12 +4,24 @@ declare(strict_types = 1);
 namespace LanguageServer;
 
 use LanguageServer\Protocol\Message;
+use Sabre\Event\{
+    Loop,
+    Promise
+};
 use RuntimeException;
 
 class ProtocolStreamWriter implements ProtocolWriter
 {
+    /**
+     * @var resource $output
+     */
     private $output;
 
+    /**
+     * @var array $messages
+     */
+    private $messages = [];
+
     /**
      * @param resource $output
      */
@@ -22,26 +34,58 @@ class ProtocolStreamWriter implements ProtocolWriter
      * Sends a Message to the client
      *
      * @param Message $msg
-     * @return void
+     * @return Promise Resolved when the message has been fully written out to the output stream
      */
     public function write(Message $msg)
     {
-        $data = (string)$msg;
-        $msgSize = strlen($data);
-        $totalBytesWritten = 0;
+        // if the message queue is currently empty, register a write handler.
+        if (empty($this->messages)) {
+            Loop\addWriteStream($this->output, function () {
+                $this->flush();
+            });
+        }
 
-        while ($totalBytesWritten < $msgSize) {
-            error_clear_last();
-            $bytesWritten = @fwrite($this->output, substr($data, $totalBytesWritten));
-            if ($bytesWritten === false) {
-                $error = error_get_last();
-                if ($error !== null) {
-                    throw new RuntimeException('Could not write message: ' . error_get_last()['message']);
-                } else {
-                    throw new RuntimeException('Could not write message');
-                }
+        $promise = new Promise();
+        $this->messages[] = [
+            'message' => (string)$msg,
+            'promise' => $promise
+        ];
+        return $promise;
+    }
+
+    /**
+     * Writes pending messages to the output stream.
+     *
+     * @return void
+     */
+    private function flush()
+    {
+        $keepWriting = true;
+        while ($keepWriting) {
+            $message = $this->messages[0]['message'];
+            $promise = $this->messages[0]['promise'];
+
+            $bytesWritten = @fwrite($this->output, $message);
+
+            if ($bytesWritten > 0) {
+                $message = substr($message, $bytesWritten);
+            }
+
+            // Determine if this message was completely sent
+            if (strlen($message) === 0) {
+                array_shift($this->messages);
+
+                // This was the last message in the queue, remove the write handler.
+                if (count($this->messages) === 0) {
+                    Loop\removeWriteStream($this->output);
+                    $keepWriting = false;
+                }
+
+                $promise->fulfill();
+            } else {
+                $this->messages[0]['message'] = $message;
+                $keepWriting = false;
             }
-            $totalBytesWritten += $bytesWritten;
         }
     }
 }
diff --git a/tests/ProtocolStreamWriterTest.php b/tests/ProtocolStreamWriterTest.php
index 90ef32d..b481c3b 100644
--- a/tests/ProtocolStreamWriterTest.php
+++ b/tests/ProtocolStreamWriterTest.php
@@ -7,6 +7,7 @@ use PHPUnit\Framework\TestCase;
 use LanguageServer\ProtocolStreamWriter;
 use LanguageServer\Protocol\Message;
 use AdvancedJsonRpc\{Request as RequestBody};
+use Sabre\Event\Loop;
 
 class ProtocolStreamWriterTest extends TestCase
 {
@@ -21,7 +22,14 @@ class ProtocolStreamWriterTest extends TestCase
         $msg = new Message(new RequestBody(1, 'aMethod', ['arg' => str_repeat('X', 100000)]));
         $msgString = (string)$msg;
 
-        $writer->write($msg);
+        $promise = $writer->write($msg);
+        $promise->then(function () {
+            Loop\stop();
+        }, function () {
+            Loop\stop();
+        });
+
+        Loop\run();
 
         fclose($writeHandle);