Make WebSocket able to manage arbitrary feedback to end-user

While previous implementation was able to send two independent messages, now we can send an arbitrary amount of independent messages.

website/index.php

@@ -9,11 +9,28 @@
 
 See <?php echoUrl('https://gitea.lemnoslife.com/Benjamin_Loison/YouTube_captions_search_engine'); ?> for more information.<br/>
 
-<input type="text" pattern="[A-Za-z0-9]+" placeholder="Your alphanumeric search"></input>
-<button>Search</button>
+<form id="form">
+    <input type="text" autofocus id="search" pattern="[A-Za-z0-9-_ ]+" placeholder="Your alphanumeric search"></input>
+    <input type="submit" value="Search">
+</form>
 
 <script>
-    var conn = new WebSocket('wss://crawler.yt.lemnoslife.com:443/websocket');
+    var firstRun = true;
+    var conn;
+
+    function search(event) {
+        event.preventDefault();
+        const query = document.getElementById('search').value;
+        if (firstRun) {
+            firstRun = false;
+            conn = new WebSocket('wss://crawler.yt.lemnoslife.com/websocket');
             conn.onmessage = function(e) { console.log(e.data); };
-    conn.onopen = function(e) { conn.send('Hello Me!'); };
+            conn.onopen = function(e) { conn.send(query); };
+        } else {
+            conn.send(query);
+        }
+    }
+
+    var form = document.getElementById('form');
+    form.addEventListener('submit', search);
 </script>

website/search.py

@@ -0,0 +1,28 @@
+#!/usr/bin/python3
+
+import sys, time, fcntl, os
+
+clientId = sys.argv[1]
+message = sys.argv[2]
+
+clientFilePath = f'users/{clientId}.txt'
+
+def write(s):
+    f = open(clientFilePath, 'w+')
+    try:
+        fcntl.flock(f, fcntl.LOCK_EX)
+        if f.read() == '':
+            f.write(s)
+        else:
+            f.close()
+            time.sleep(1)
+            write(s)
+    except Exception as e:
+        print(e)
+    f.close()
+
+for i in range(10):
+    write(f'{i}: {message}')
+    time.sleep(2)
+
+os.remove(clientFilePath)

website/users/.gitignore

@@ -0,0 +1,5 @@
+# Ignore everything in this directory
+*
+# Except this file
+!.gitignore
+

website/websocket.php

@@ -8,41 +8,147 @@ use React\EventLoop\Timer\Timer;
 // Make sure composer dependencies have been installed
 require __DIR__ . '/vendor/autoload.php';
 
-/**
- * Send any incoming messages to all connected clients
- */
-class MyChat implements MessageComponentInterface
+class Client
+{
+    public $id;
+    public $timer;
+    public $pid;
+
+    public function __construct($id)
+    {
+        $this->id = $id;
+    }
+
+    public function free($loop)
+    {
+        $loop->cancelTimer($this->timer);
+        // Should in theory verify that the pid wasn't re-assigned.
+        posix_kill($this->pid, SIGTERM);
+        $clientFilePath = getClientFilePath($this->id);
+        if (file_exists($clientFilePath)) {
+            $fp = fopen($clientFilePath, "r+");
+            if (flock($fp, LOCK_EX, $WAIT_IF_LOCKED)) {   // acquire an exclusive lock
+                unlink($clientFilePath); // delete file
+                flock($fp, LOCK_UN);     // release the lock
+            } else {
+                echo "Couldn't get the lock!";
+            }
+            fclose($fp);
+        }
+    }
+}
+
+$WAIT_IF_LOCKED = 1;
+
+define('USERS_FOLDER', 'users/');
+
+foreach (array_slice(scandir(USERS_FOLDER), 3) as $file) {
+    unlink(USERS_FOLDER . $file);
+}
+
+function getClientFilePath($clientId)
+{
+    return USERS_FOLDER . "$clientId.txt";
+}
+
+// Current implementation may add latency across users.
+class MyProcess implements MessageComponentInterface
 {
     protected $clients;
     private $loop;
+    private $newClientId;
+    private $newClientIdSem;
 
     public function __construct(LoopInterface $loop)
     {
         $this->clients = new \SplObjectStorage();
         $this->loop = $loop;
+        $this->newClientId = 0;
+        $this->newClientIdSem = sem_get(1, 1);
+    }
+
+    private function newClient()
+    {
+        if (sem_acquire($this->newClientIdSem)) {
+            $clientId = $this->newClientId++;
+            sem_release($this->newClientIdSem);
+            return new Client($clientId);
+        } else {
+            exit('`onOpen` error');
+        }
     }
 
     public function onOpen(ConnectionInterface $conn)
     {
-        $this->clients->attach($conn);
+        $client = $this->newClient();
+        $this->clients->attach($conn, $client);
     }
 
     public function onMessage(ConnectionInterface $from, $msg)
     {
-        $from->send($msg);
-        $this->loop->addTimer(Timer::MIN_INTERVAL * 10, function() use ($from) {
-            sleep(5);
-            $from->send('Proceeded!');
+        if (preg_match("/^[a-zA-Z0-9-_ ]+$/", $msg) !== 1) {
+            return;
+        }
+        $client = $this->clients->offsetGet($from);
+        // If a previous request was received, we execute the new one with another client for simplicity.
+        if ($client->pid !== null) {
+            $client->free($this->loop);
+            $client = $this->newClient();
+        }
+        $clientId = $client->id;
+        $clientFilePath = getClientFilePath($clientId);
+        file_put_contents($clientFilePath, '');
+        $client->pid = exec("./search.py $clientId '$msg' > /dev/null & echo $!");
+        $client->timer = $this->loop->addPeriodicTimer(1, function () use ($from, $clientId, $clientFilePath, $client) {
+            echo "Checking news from $clientId\n";
+            if (file_exists($clientFilePath)) {
+                $fp = fopen($clientFilePath, "r+");
+                $read = null;
+                if (flock($fp, LOCK_EX, $WAIT_IF_LOCKED)) { // acquire an exclusive lock
+                    $read = fread($fp, 1_000_000);
+                    ftruncate($fp, 0);     // truncate file
+                    fflush($fp);           // flush output before releasing the lock
+                    flock($fp, LOCK_UN);   // release the lock
+                } else {
+                    echo "Couldn't get the lock!";
+                }
+                fclose($fp);
+
+                if ($read !== null && $read !== '') {
+                    $from->send($read);
+                }
+            } else {
+                $this->loop->cancelTimer($client->timer);
+            }
         });
     }
 
     public function onClose(ConnectionInterface $conn)
     {
+        $client = $this->clients->offsetGet($conn);
+        $clientId = $client->id;
+        $client->free($this->loop);
+        echo "$clientId disconnected\n";
+        /*$this->loop->cancelTimer($client->timer);
+        // Should in theory verify that the pid wasn't re-assigned.
+        posix_kill($client->pid, SIGTERM);
+        $clientFilePath = getClientFilePath($clientId);
+        if (file_exists($clientFilePath)) {
+            $fp = fopen($clientFilePath, "r+");
+            if (flock($fp, LOCK_EX, $WAIT_IF_LOCKED)) {   // acquire an exclusive lock
+                unlink($clientFilePath); // delete file
+                flock($fp, LOCK_UN);     // release the lock
+            } else {
+                echo "Couldn't get the lock!";
+            }
+            fclose($fp);
+        }*/
         $this->clients->detach($conn);
     }
 
     public function onError(ConnectionInterface $conn, \Exception $e)
     {
+        echo '`onError`';
         $conn->close();
     }
 }
@@ -51,5 +157,5 @@ $loop = \React\EventLoop\Factory::create();
 
 // Run the server application through the WebSocket protocol on port 4430
 $app = new Ratchet\App('crawler.yt.lemnoslife.com', 4430, '127.0.0.1', $loop);
-$app->route('/websocket', new MyChat($loop), array('*'));
+$app->route('/websocket', new MyProcess($loop), array('*'));
 $app->run();