fix: make bpn response failures diagnosable

src/BusProNet/ApiClient.php

@@ -602,10 +602,12 @@ class ApiClient
             'port' => $this->selectedPort,
         ]);
         $this->send($socket, $body);
-        $response = $this->receive($socket);
-        $this->disconnect($socket);
 
-        $responseXml = substr($response, 10);
+        try {
+            $responseXml = $this->receive($socket);
+        } finally {
+            $this->disconnect($socket);
+        }
 
         if (true === $debug || true === $this->config['debug']) {
             $this->dumpXmlToFile('response', $requestId, $responseXml);
@@ -714,18 +716,12 @@ class ApiClient
         ]);
 
         $this->send($socket, $body);
-        $response = $this->receive($socket);
-        $this->disconnect($socket);
 
-        // message length (10 bytes) is prepended to actual message
-        $xml = substr($response, 10);
-
-        if ('' === $xml) {
-            $this->logger->error('Empty response body received from API (header-only response)', [
-                'request_id' => $requestId,
-                'raw_length' => strlen($response),
-            ]);
-            throw new ApiClientException('Empty response body received from API');
+        try {
+            // the length header is consumed and verified by receive(), this is the payload
+            $xml = $this->receive($socket);
+        } finally {
+            $this->disconnect($socket);
         }
 
         if (true === $debug || true === $this->config['debug']) {
@@ -735,14 +731,19 @@ class ApiClient
         try {
             return $this->responseParser->parseXmlString($type, $xml, $additionalArgs);
         } catch (ResponseParserException $e) {
+            // Keep the evidence even outside debug mode: without the raw response a parse
+            // failure is not diagnosable after the fact. app:cleanup:xml-dumps prunes it.
             $this->dumpXmlToFile('response', $requestId, $xml);
+
+            $this->logger->error('Unable to parse response received from API', [
+                'request_id' => $requestId,
+                'type' => $type,
+                'response_length' => strlen($xml),
+                'error_message' => $e->getMessage(),
+            ]);
+
+            throw new ApiClientException('Unable to parse response received from API: '.$e->getMessage(), 0, $e);
         }
-
-        $this->logger->error('Unexpected response received from API', [
-            'request_id' => $requestId,
-        ]);
-
-        throw new ApiClientException('Unexpected response received from API');
     }
 
     /**
@@ -773,10 +774,12 @@ class ApiClient
         ]);
 
         $this->send($socket, $body);
-        $response = $this->receive($socket);
-        $this->disconnect($socket);
 
-        $xml = substr($response, 10);
+        try {
+            $xml = $this->receive($socket);
+        } finally {
+            $this->disconnect($socket);
+        }
 
         if (true === $this->config['debug']) {
             $this->dumpXmlToFile('response', $requestId, $xml);
@@ -898,8 +901,14 @@ class ApiClient
     }
 
     /**
+     * Reads a single response message and returns its payload. The protocol prepends the
+     * payload length as a 10 byte header, so the announced length is compared against what
+     * actually arrived: a peer closing mid-stream would otherwise yield a silently
+     * truncated body that only surfaces later as an unexplained parse failure.
+     *
      * @param resource $socket
      *
+     * @throws ApiClientException
      * @throws TimeoutException
      * @throws ImmediateConnectionCloseException
      */
@@ -963,7 +972,47 @@ class ApiClient
             throw new ImmediateConnectionCloseException('Server closed connection without sending data');
         }
 
-        return $response;
+        return $this->extractPayload($response);
+    }
+
+    /**
+     * @throws ApiClientException
+     */
+    private function extractPayload(string $response): string
+    {
+        if (10 > strlen($response)) {
+            $this->logger->error('Incomplete response header received from API', [
+                'bytes_received' => strlen($response),
+                'port' => $this->selectedPort,
+            ]);
+
+            throw new ApiClientException(sprintf('Incomplete response header, got %d of 10 bytes', strlen($response)));
+        }
+
+        $header = substr($response, 0, 10);
+        $announcedLength = (int) trim($header);
+        $payload = substr($response, 10);
+
+        if (1 > $announcedLength) {
+            $this->logger->error('Empty response body announced by API', [
+                'header' => trim($header),
+                'port' => $this->selectedPort,
+            ]);
+
+            throw new ApiClientException(sprintf('Response announced an empty body (header "%s")', trim($header)));
+        }
+
+        if (strlen($payload) !== $announcedLength) {
+            $this->logger->error('Truncated response received from API', [
+                'bytes_received' => strlen($payload),
+                'announced_length' => $announcedLength,
+                'port' => $this->selectedPort,
+            ]);
+
+            throw new ApiClientException(sprintf('Truncated response, got %d of %d announced bytes', strlen($payload), $announcedLength));
+        }
+
+        return $payload;
     }
 
     /** @param resource $socket */