Handling the maximum length of a Telegram message (#1616)

* Handling the maximum length of a Telegram message

The maximum allowed length of a Telegram message - 4096 symbols (https://core.telegram.org/bots/api#message, 'text' field). 
Longer messages are not delivered.
Therefore, I implemented splitting too long message into several (with a 1 second delay between sending according to the documentation - https://core.telegram.org/bots/faq#my-bot-is-hitting-limits-how-do-i-avoid-this) as the default behavior. 
An additional option that you can enable by truncateLongMessage is to leave one message, but truncate it to the maximum length allowed.

* Changed handling of long messages (default - truncation, delay - optional)

* PSR-12 code formatting

src/Monolog/Handler/TelegramBotHandler.php

@@ -43,6 +43,11 @@ class TelegramBotHandler extends AbstractProcessingHandler
         'Markdown', // legacy mode without underline and strikethrough, use MarkdownV2 instead
     ];
 
+    /**
+     * The maximum number of characters allowed in a message according to the Telegram api documentation
+     */
+    private const MAX_MESSAGE_LENGTH = 4096;
+
     /**
      * Telegram bot access token provided by BotFather.
      * Create telegram bot with https://telegram.me/BotFather and use access token from it.
@@ -78,18 +83,37 @@ class TelegramBotHandler extends AbstractProcessingHandler
     private $disableNotification;
 
     /**
-     * @param string $apiKey  Telegram bot access token provided by BotFather
+     * True - split a message longer than MAX_MESSAGE_LENGTH into parts and send in multiple messages.
+     * False - truncates a message that is too long.
+     * @var bool
+     */
+    private $splitLongMessages;
+
+    /**
+     * Adds 1-second delay between sending a split message (according to Telegram API to avoid 429 Too Many Requests).
+     * @var bool
+     */
+    private $delayBetweenMessages;
+
+    /**
+     * @param string $apiKey Telegram bot access token provided by BotFather
      * @param string $channel Telegram channel name
+     * @param bool $splitLongMessages Split a message longer than MAX_MESSAGE_LENGTH into parts and send in multiple messages
+     * @param bool $delayBetweenMessages Adds delay between sending a split message according to Telegram API
+     * @throws MissingExtensionException
      */
     public function __construct(
         string $apiKey,
         string $channel,
-        $level = Logger::DEBUG,
-        bool $bubble = true,
+               $level = Logger::DEBUG,
+        bool   $bubble = true,
         string $parseMode = null,
-        bool $disableWebPagePreview = null,
-        bool $disableNotification = null
-    ) {
+        bool   $disableWebPagePreview = null,
+        bool   $disableNotification = null,
+        bool   $splitLongMessages = false,
+        bool   $delayBetweenMessages = false
+    )
+    {
         if (!extension_loaded('curl')) {
             throw new MissingExtensionException('The curl extension is needed to use the TelegramBotHandler');
         }
@@ -101,6 +125,8 @@ class TelegramBotHandler extends AbstractProcessingHandler
         $this->setParseMode($parseMode);
         $this->disableWebPagePreview($disableWebPagePreview);
         $this->disableNotification($disableNotification);
+        $this->splitLongMessages($splitLongMessages);
+        $this->delayBetweenMessages($delayBetweenMessages);
     }
 
     public function setParseMode(string $parseMode = null): self
@@ -128,6 +154,31 @@ class TelegramBotHandler extends AbstractProcessingHandler
         return $this;
     }
 
+    /**
+     * True - split a message longer than MAX_MESSAGE_LENGTH into parts and send in multiple messages.
+     * False - truncates a message that is too long.
+     * @param bool $splitLongMessages
+     * @return $this
+     */
+    public function splitLongMessages(bool $splitLongMessages = false): self
+    {
+        $this->splitLongMessages = $splitLongMessages;
+
+        return $this;
+    }
+
+    /**
+     * Adds 1-second delay between sending a split message (according to Telegram API to avoid 429 Too Many Requests).
+     * @param bool $delayBetweenMessages
+     * @return $this
+     */
+    public function delayBetweenMessages(bool $delayBetweenMessages = false): self
+    {
+        $this->delayBetweenMessages = $delayBetweenMessages;
+
+        return $this;
+    }
+
     /**
      * {@inheritDoc}
      */
@@ -150,7 +201,7 @@ class TelegramBotHandler extends AbstractProcessingHandler
         }
 
         if (!empty($messages)) {
-            $this->send((string) $this->getFormatter()->formatBatch($messages));
+            $this->send((string)$this->getFormatter()->formatBatch($messages));
         }
     }
 
@@ -167,6 +218,19 @@ class TelegramBotHandler extends AbstractProcessingHandler
      * @param string $message
      */
     protected function send(string $message): void
+    {
+        $messages = $this->handleMessageLength($message);
+
+        foreach ($messages as $key => $msg) {
+            if ($this->delayBetweenMessages && $key > 0) {
+                sleep(1);
+            }
+
+            $this->sendCurl($msg);
+        }
+    }
+
+    protected function sendCurl(string $message): void
     {
         $ch = curl_init();
         $url = self::BOT_API . $this->apiKey . '/SendMessage';
@@ -191,4 +255,19 @@ class TelegramBotHandler extends AbstractProcessingHandler
             throw new RuntimeException('Telegram API error. Description: ' . $result['description']);
         }
     }
+
+    /**
+     * Handle a message that is too long: truncates or splits into several
+     * @param string $message
+     * @return string[]
+     */
+    private function handleMessageLength(string $message): array
+    {
+        $truncatedMarker = ' (...truncated)';
+        if (!$this->splitLongMessages && strlen($message) > self::MAX_MESSAGE_LENGTH) {
+            return [substr($message, 0, self::MAX_MESSAGE_LENGTH - strlen($truncatedMarker)) . $truncatedMarker];
+        }
+
+        return str_split($message, self::MAX_MESSAGE_LENGTH);
+    }
 }