fix: use Google Cloud API key for classic mode + translation verification

Two critical fixes:

1. Provider "google" (default classic mode) now checks for a Google Cloud
   API key (GOOGLE_CLOUD_API_KEY in env or admin settings). If present,
   uses GoogleCloudTranslationProvider (official API). Previously it
   always fell through to deep_translator (free scraper) which gets
   blocked in production, silently returning untranslated text.

2. Added translation verification: each translator now tracks how many
   texts were attempted vs actually changed. If 0 texts were translated,
   the job is marked as FAILED with a clear error message instead of
   returning the original file as "completed".

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

routes/translate_routes.py

@@ -951,7 +951,21 @@ async def _run_translation_job(
         translation_provider = None
         _p = provider.lower()
 
-        if _p in ("openrouter", "llm") and api_key:
+        # "google" (default classic mode): use Google Cloud API key if available,
+        # otherwise fall back to deep_translator (legacy, no key).
+        if _p == "google":
+            gc_key = _cfg(
+                getattr(_admin_cfg.google_cloud, "api_key", None),
+                "GOOGLE_CLOUD_API_KEY",
+            )
+            if gc_key:
+                from services.providers.google_cloud_provider import LegacyGoogleCloudAdapter
+                translation_provider = LegacyGoogleCloudAdapter(gc_key)
+                logger.info("google_provider_using_cloud_api", job_id=job_id)
+            else:
+                logger.info("google_provider_no_cloud_key_using_legacy", job_id=job_id)
+
+        elif _p in ("openrouter", "llm") and api_key:
             translation_provider = OpenRouterTranslationProvider(
                 api_key, model, full_prompt
             )
@@ -1114,6 +1128,30 @@ async def _run_translation_job(
         else:
             raise ValueError(f"Unsupported file type: {file_extension}")
 
+        # ── Verify translation actually produced results ──
+        if not output_path.exists() or output_path.stat().st_size == 0:
+            error_msg = "Translation failed: output file is empty or missing. The translation provider may be unavailable."
+            logger.error(f"Job {job_id}: {error_msg}")
+            tracker.set_error(error_msg)
+            return
+
+        stats = job_translator.get_translation_stats()
+        attempted = stats.get("attempted", 0)
+        changed = stats.get("changed", 0)
+
+        if attempted > 0:
+            ratio = changed / attempted
+            logger.info(f"Job {job_id}: translation stats — {changed}/{attempted} texts changed ({ratio:.0%})")
+            if ratio < 0.15 and changed == 0:
+                error_msg = (
+                    f"Translation failed: 0 out of {attempted} texts were translated. "
+                    f"The provider ({provider}) may be unavailable or misconfigured. "
+                    f"Check your API keys in admin settings."
+                )
+                logger.error(f"Job {job_id}: {error_msg}")
+                tracker.set_error(error_msg)
+                return
+
         if user_id:
             await tier_quota_service.increment_on_success(user_id)
             # Persist monthly usage counters in PostgreSQL (docs + pages)

translators/excel_translator.py

@@ -107,6 +107,7 @@ class ExcelTranslator:
         self._provider = provider
         self.formula_pattern = re.compile(r"=.*")
         self._custom_prompt: Optional[str] = None
+        self._translation_stats = {"attempted": 0, "changed": 0}
 
     def set_provider(self, provider: TranslationProvider) -> None:
         """Set the translation provider."""
@@ -387,26 +388,26 @@ class ExcelTranslator:
     def _batch_translate(
         self, texts: List[str], target_language: str, source_language: str = "auto"
     ) -> List[str]:
-        """
-        Batch translate using new provider interface.
-
-        Args:
-            texts: List of texts to translate
-            target_language: Target language code
-            source_language: Source language code
-
-        Returns:
-            List of translated texts (same order as input)
-        """
         if not texts:
             return []
 
+        non_empty = [t for t in texts if t and t.strip()]
+        self._translation_stats["attempted"] += len(non_empty)
+
         if self._provider is not None:
-            return self._translate_with_provider(
+            translated = self._translate_with_provider(
                 texts, target_language, source_language
             )
+        else:
+            translated = self._translate_with_legacy(texts, target_language, source_language)
 
-        return self._translate_with_legacy(texts, target_language, source_language)
+        changed = sum(1 for orig, trans in zip(texts, translated) if orig != trans and trans.strip())
+        self._translation_stats["changed"] += changed
+
+        return translated
+
+    def get_translation_stats(self) -> dict:
+        return dict(self._translation_stats)
 
     def _translate_with_provider(
         self, texts: List[str], target_language: str, source_language: str

translators/pdf_translator.py

@@ -63,6 +63,7 @@ class PDFTranslator:
     def __init__(self, provider=None):
         self._provider = provider
         self._font_path: Optional[str] = None
+        self._translation_stats = {"attempted": 0, "changed": 0}
 
     def _get_font_path(self) -> Optional[str]:
         """Resolve a Unicode-capable TTF/OTF font file."""
@@ -825,18 +826,31 @@ class PDFTranslator:
         self, texts: List[str], target_language: str, source_language: str
     ) -> List[str]:
         """Translate a batch of texts."""
+        non_empty = [t for t in texts if t and t.strip()]
+        self._translation_stats["attempted"] += len(non_empty)
+
+        translated = None
         if self._provider is not None:
             try:
-                return self._provider.translate_batch(texts, target_language, source_language)
+                translated = self._provider.translate_batch(texts, target_language, source_language)
             except Exception as e:
                 logger.warning("provider_translate_failed", error=str(e))
 
-        from services.translation_service import translation_service
-        try:
-            return translation_service.translate_batch(texts, target_language, source_language)
-        except Exception as e:
-            logger.warning("legacy_translate_failed", error=str(e))
-            return texts
+        if translated is None:
+            from services.translation_service import translation_service
+            try:
+                translated = translation_service.translate_batch(texts, target_language, source_language)
+            except Exception as e:
+                logger.warning("legacy_translate_failed", error=str(e))
+                translated = texts
+
+        changed = sum(1 for orig, trans in zip(texts, translated) if orig != trans and trans.strip())
+        self._translation_stats["changed"] += changed
+
+        return translated
+
+    def get_translation_stats(self) -> dict:
+        return dict(self._translation_stats)
 
     def _validate_file(self, file_path: Path) -> None:
         if not file_path.exists():

translators/pptx_translator.py

@@ -152,6 +152,7 @@ class PowerPointTranslator:
         """
         self._provider = provider
         self._custom_prompt: Optional[str] = None
+        self._translation_stats = {"attempted": 0, "changed": 0}
 
     def set_provider(self, provider: TranslationProvider) -> None:
         """Set the translation provider."""
@@ -381,26 +382,26 @@ class PowerPointTranslator:
     def _batch_translate(
         self, texts: List[str], target_language: str, source_language: str = "auto"
     ) -> List[str]:
-        """
-        Batch translate using new provider interface.
-
-        Args:
-            texts: List of texts to translate
-            target_language: Target language code
-            source_language: Source language code
-
-        Returns:
-            List of translated texts (same order as input)
-        """
         if not texts:
             return []
 
+        non_empty = [t for t in texts if t and t.strip()]
+        self._translation_stats["attempted"] += len(non_empty)
+
         if self._provider is not None:
-            return self._translate_with_provider(
+            translated = self._translate_with_provider(
                 texts, target_language, source_language
             )
+        else:
+            translated = self._translate_with_legacy(texts, target_language, source_language)
 
-        return self._translate_with_legacy(texts, target_language, source_language)
+        changed = sum(1 for orig, trans in zip(texts, translated) if orig != trans and trans.strip())
+        self._translation_stats["changed"] += changed
+
+        return translated
+
+    def get_translation_stats(self) -> dict:
+        return dict(self._translation_stats)
 
     def _translate_with_provider(
         self, texts: List[str], target_language: str, source_language: str

translators/word_translator.py

@@ -172,6 +172,7 @@ class WordTranslator:
         """
         self._provider = provider
         self._custom_prompt: Optional[str] = None
+        self._translation_stats = {"attempted": 0, "changed": 0}
 
     def set_provider(self, provider: TranslationProvider) -> None:
         """Set the translation provider."""
@@ -439,12 +440,23 @@ class WordTranslator:
         if not texts:
             return []
 
+        non_empty = [t for t in texts if t and t.strip()]
+        self._translation_stats["attempted"] += len(non_empty)
+
         if self._provider is not None:
-            return self._translate_with_provider(
+            translated = self._translate_with_provider(
                 texts, target_language, source_language
             )
+        else:
+            translated = self._translate_with_legacy(texts, target_language, source_language)
 
-        return self._translate_with_legacy(texts, target_language, source_language)
+        changed = sum(1 for orig, trans in zip(texts, translated) if orig != trans and trans.strip())
+        self._translation_stats["changed"] += changed
+
+        return translated
+
+    def get_translation_stats(self) -> dict:
+        return dict(self._translation_stats)
 
     def _translate_with_provider(
         self, texts: List[str], target_language: str, source_language: str