fix: make BusProNet response failures diagnosable and non-fatal

src/BusProNet/ApiClient.php

@@ -162,17 +162,36 @@ class ApiClient
             $this->config['max_retries']
         );
         $this->send($socket, $body);
-        $response = $this->receive($socket);
-        $this->disconnect($socket);
 
-        // message length (10 bytes) is prepended to actual message
-        $xml = substr($response, 10);
+        try {
+            // the length header is consumed by receive(), this is the payload
+            $xml = $this->receive($socket);
+        } finally {
+            $this->disconnect($socket);
+        }
 
         if (true === $this->config['debug']) {
             $this->dumpXmlToFile('response', $requestId, $xml);
         }
 
-        return $this->responseParser->parseXmlString($type, $xml);
+        try {
+            return $this->responseParser->parseXmlString($type, $xml);
+        } 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.
+            if (true !== $this->config['debug']) {
+                $this->dumpXmlToFile('response', $requestId, $xml);
+            }
+
+            $this->logger->error('Unable to parse BusProNet response', [
+                'request_id' => $requestId,
+                'type' => $type,
+                'response_length' => strlen($xml),
+                'error_message' => $e->getMessage(),
+            ]);
+
+            throw $e;
+        }
     }
 
     private function dumpXmlToFile(string $type, string $requestId, string $body): void

src/BusProNet/ApiClientTrait.php

@@ -58,15 +58,58 @@ trait ApiClientTrait
         fwrite($socket, $send);
     }
 
+    /**
+     * Reads a single response message. The protocol prepends the payload length as a
+     * 10 byte header, so read exactly that many bytes rather than guessing at EOF:
+     * a peer that closes mid-stream would otherwise yield a silently truncated body.
+     *
+     * @throws ApiClientException
+     */
     private function receive($socket): string
     {
-        $response = '';
+        $header = $this->readBytes($socket, 10);
 
-        while (false === feof($socket)) {
-            $response .= fread($socket, 4096);
+        if (10 !== strlen($header)) {
+            throw new ApiClientException(sprintf('Incomplete response header, got %d of 10 bytes', strlen($header)));
         }
 
-        return $response;
+        $expectedLength = (int) trim($header);
+
+        if (1 > $expectedLength) {
+            throw new ApiClientException(sprintf('Response announced an empty body (header "%s")', trim($header)));
+        }
+
+        $body = $this->readBytes($socket, $expectedLength);
+
+        if (strlen($body) !== $expectedLength) {
+            throw new ApiClientException(sprintf('Truncated response, got %d of %d announced bytes', strlen($body), $expectedLength));
+        }
+
+        return $body;
+    }
+
+    /**
+     * @throws ApiClientException
+     */
+    private function readBytes($socket, int $length): string
+    {
+        $buffer = '';
+
+        while (strlen($buffer) < $length && false === feof($socket)) {
+            $chunk = fread($socket, min(4096, $length - strlen($buffer)));
+
+            if (false === $chunk || '' === $chunk) {
+                if (true === (stream_get_meta_data($socket)['timed_out'] ?? false)) {
+                    throw new ApiClientException(sprintf('Timed out reading response after %d of %d bytes', strlen($buffer), $length));
+                }
+
+                break;
+            }
+
+            $buffer .= $chunk;
+        }
+
+        return $buffer;
     }
 
     private function disconnect($socket): void

src/BusProNet/DataProvider/CountryDataProvider.php

@@ -6,6 +6,7 @@ use App\BusProNet\ApiClient;
 use App\BusProNet\ApiClientException;
 use App\BusProNet\Model\Country;
 use App\BusProNet\Model\NotificationResponse;
+use App\BusProNet\ResponseParserException;
 use Psr\Log\LoggerInterface;
 use Symfony\Contracts\Cache\CacheInterface;
 use Symfony\Contracts\Cache\ItemInterface;
@@ -35,7 +36,8 @@ class CountryDataProvider
 
                 return $response->getItems();
             });
-        } catch (ApiClientException $e) {
+        } catch (ApiClientException|ResponseParserException $e) {
+            $this->logger->error('Unable to fetch country base data from BusProNet: '.$e->getMessage());
             $countries = [];
         }
 

src/BusProNet/DataProvider/HotelDataProvider.php

@@ -6,6 +6,7 @@ use App\BusProNet\ApiClient;
 use App\BusProNet\ApiClientException;
 use App\BusProNet\Model\Hotel;
 use App\BusProNet\Model\NotificationResponse;
+use App\BusProNet\ResponseParserException;
 use Psr\Cache\InvalidArgumentException;
 use Psr\Log\LoggerInterface;
 use Symfony\Contracts\Cache\CacheInterface;
@@ -36,7 +37,8 @@ class HotelDataProvider
 
                 return $response->getItems();
             });
-        } catch (ApiClientException|InvalidArgumentException $e) {
+        } catch (ApiClientException|InvalidArgumentException|ResponseParserException $e) {
+            $this->logger->error('Unable to fetch hotel base data from BusProNet: '.$e->getMessage());
             $hotels = [];
         }
 

src/BusProNet/DataProvider/PickupDataProvider.php

@@ -6,6 +6,7 @@ use App\BusProNet\ApiClient;
 use App\BusProNet\ApiClientException;
 use App\BusProNet\Model\NotificationResponse;
 use App\BusProNet\Model\Pickup;
+use App\BusProNet\ResponseParserException;
 use Psr\Log\LoggerInterface;
 use Symfony\Contracts\Cache\CacheInterface;
 use Symfony\Contracts\Cache\ItemInterface;
@@ -35,7 +36,8 @@ class PickupDataProvider
 
                 return $response->getItems();
             });
-        } catch (ApiClientException $e) {
+        } catch (ApiClientException|ResponseParserException $e) {
+            $this->logger->error('Unable to fetch pickup base data from BusProNet: '.$e->getMessage());
             $pickups = [];
         }
 

src/BusProNet/ResponseParser.php

@@ -30,10 +30,7 @@ class ResponseParser
      */
     public function parseXmlString(string $type, string $content): mixed
     {
-        $xml = simplexml_load_string($content);
-        if (false === $xml) {
-            throw new ResponseParserException('Unable to parse XML response');
-        }
+        $xml = $this->loadXml($content);
 
         // Override type when present in XML to catch error responses
         $responseType = $type;
@@ -65,7 +62,7 @@ class ResponseParser
                 return $this->createHotelsResponse($xml);
         }
 
-        throw new ResponseParserException('Unable to parse XML response');
+        throw new ResponseParserException(sprintf('Unrecognised BusProNet response type "%s"', $responseType));
     }
 
     public function createNotificationResponse(\SimpleXMLElement $xml): NotificationResponse
@@ -302,6 +299,50 @@ class ResponseParser
         return new BaseDataResponse($hotels);
     }
 
+    /**
+     * The BusProNet endpoint can answer with an empty or truncated body. Keep the libxml
+     * reason instead of collapsing every shape of broken response into one message.
+     *
+     * @throws ResponseParserException
+     */
+    private function loadXml(string $content): \SimpleXMLElement
+    {
+        if ('' === trim($content)) {
+            throw new ResponseParserException(sprintf('Unable to parse XML response (%d bytes): empty response', strlen($content)));
+        }
+
+        $previousUseErrors = libxml_use_internal_errors(true);
+        libxml_clear_errors();
+
+        try {
+            $xml = simplexml_load_string($content);
+
+            if (false === $xml) {
+                throw new ResponseParserException(sprintf('Unable to parse XML response (%d bytes): %s', strlen($content), $this->describeLibxmlErrors()));
+            }
+
+            return $xml;
+        } finally {
+            libxml_clear_errors();
+            libxml_use_internal_errors($previousUseErrors);
+        }
+    }
+
+    private function describeLibxmlErrors(): string
+    {
+        $messages = [];
+
+        foreach (libxml_get_errors() as $error) {
+            $messages[] = sprintf('%s (line %d, column %d)', trim($error->message), $error->line, $error->column);
+        }
+
+        if ([] === $messages) {
+            return 'unknown XML error';
+        }
+
+        return implode('; ', array_unique($messages));
+    }
+
     private function resolveOptions(array $options): array
     {
         $optionsResolver = new OptionsResolver();