From 289a723d5e6abdfa1d26a2c00ac796ed904292bc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A1chym=20Tou=C5=A1ek?= <enumag@gmail.com>
Date: Sat, 2 May 2020 11:14:21 +0200
Subject: [PATCH] Add AsyncFileMutex (#43)

---
 .travis.yml                      |  4 +-
 composer.json                    | 11 ++++-
 src/Sync/AsyncFileMutex.php      | 84 ++++++++++++++++++++++++++++++++
 src/UvDriver.php                 |  2 +-
 test/Sync/AsyncFileMutexTest.php | 15 ++++++
 5 files changed, 111 insertions(+), 5 deletions(-)
 create mode 100644 src/Sync/AsyncFileMutex.php
 create mode 100644 test/Sync/AsyncFileMutexTest.php

diff --git a/.travis.yml b/.travis.yml
index 0f6f1fc..cee1596 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -31,9 +31,9 @@ before_install:
 
 install:
   - if [ "$TRAVIS_PHP_VERSION" = "nightly" ]; then
-      composer update -n --prefer-dist --ignore-platform-reqs;
+      composer update -n --ignore-platform-reqs;
     else
-      composer update -n --prefer-dist;
+      composer update -n;
     fi
   - composer show
 
diff --git a/composer.json b/composer.json
index 53d3dbe..40eb040 100644
--- a/composer.json
+++ b/composer.json
@@ -35,7 +35,8 @@
         "php": ">=7.1",
         "amphp/amp": "^2.2",
         "amphp/byte-stream": "^1.6.1",
-        "amphp/parallel": "^1.2"
+        "amphp/parallel": "^1.2",
+        "amphp/sync": "^1.3"
     },
     "require-dev": {
         "ext-eio": "^2",
@@ -52,7 +53,13 @@
     },
     "autoload-dev": {
         "psr-4": {
-            "Amp\\File\\Test\\": "test"
+            "Amp\\File\\Test\\": "test",
+            "Amp\\Sync\\Test\\": "vendor/amphp/sync/test"
+        }
+    },
+    "config": {
+        "preferred-install": {
+            "amphp/sync": "source"
         }
     },
     "extra": {
diff --git a/src/Sync/AsyncFileMutex.php b/src/Sync/AsyncFileMutex.php
new file mode 100644
index 0000000..7d81234
--- /dev/null
+++ b/src/Sync/AsyncFileMutex.php
@@ -0,0 +1,84 @@
+<?php
+
+namespace Amp\File\Sync;
+
+use Amp\Coroutine;
+use Amp\Delayed;
+use Amp\File\FilesystemException;
+use Amp\Promise;
+use Amp\Sync\Lock;
+use Amp\Sync\Mutex;
+use Amp\Sync\SyncException;
+use function Amp\File\open;
+use function Amp\File\unlink;
+
+final class AsyncFileMutex implements Mutex
+{
+    private const LATENCY_TIMEOUT = 10;
+
+    /** @var string The full path to the lock file. */
+    private $fileName;
+
+    /**
+     * @param string $fileName Name of temporary file to use as a mutex.
+     */
+    public function __construct(string $fileName)
+    {
+        $this->fileName = $fileName;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function acquire(): Promise
+    {
+        return new Coroutine($this->doAcquire());
+    }
+
+    /**
+     * @coroutine
+     *
+     * @return \Generator
+     */
+    private function doAcquire(): \Generator
+    {
+        // Try to create the lock file. If the file already exists, someone else
+        // has the lock, so set an asynchronous timer and try again.
+        while (true) {
+            try {
+                $file = yield open($this->fileName, 'x');
+
+                break;
+            } catch (FilesystemException $exception) {
+                yield new Delayed(self::LATENCY_TIMEOUT);
+            }
+        }
+
+        // Return a lock object that can be used to release the lock on the mutex.
+        $lock = new Lock(0, function (): void {
+            $this->release();
+        });
+
+        yield $file->close();
+
+        return $lock;
+    }
+
+    /**
+     * Releases the lock on the mutex.
+     */
+    private function release(): void
+    {
+        unlink($this->fileName)->onResolve(
+            function (?\Throwable $exception): void {
+                if ($exception !== null) {
+                    throw new SyncException(
+                        'Failed to unlock the mutex file: ' . $this->fileName,
+                        0,
+                        $exception
+                    );
+                }
+            }
+        );
+    }
+}
diff --git a/src/UvDriver.php b/src/UvDriver.php
index 887898e..1fccfbe 100644
--- a/src/UvDriver.php
+++ b/src/UvDriver.php
@@ -57,7 +57,7 @@ final class UvDriver implements Driver
 
         $openArr = [$mode, $path, $deferred];
         \uv_fs_open($this->loop, $path, $flags, $chmod, function ($fh) use ($openArr): void {
-            if ($fh) {
+            if (\is_resource($fh)) {
                 $this->onOpenHandle($fh, $openArr);
             } else {
                 [, $path, $deferred] = $openArr;
diff --git a/test/Sync/AsyncFileMutexTest.php b/test/Sync/AsyncFileMutexTest.php
new file mode 100644
index 0000000..f41f135
--- /dev/null
+++ b/test/Sync/AsyncFileMutexTest.php
@@ -0,0 +1,15 @@
+<?php declare(strict_types = 1);
+
+namespace Amp\File\Test\Sync;
+
+use Amp\File\Sync\AsyncFileMutex;
+use Amp\Sync\Mutex;
+use Amp\Sync\Test\AbstractMutexTest;
+
+final class AsyncFileMutexTest extends AbstractMutexTest
+{
+    public function createMutex(): Mutex
+    {
+        return new AsyncFileMutex(\tempnam(\sys_get_temp_dir(), 'mutex-') . '.lock');
+    }
+}