feat: integrate Google Generative AI as a fallback for OpenRouter in translation and chat services

backend/app/services/ai_chat_service.py

@@ -7,6 +7,7 @@ from app.services.openrouter_config_service import (
     extract_openrouter_text,
     get_openrouter_settings,
 )
+from app.services import google_ai_service
 
 logger = logging.getLogger(__name__)
 
@@ -33,11 +34,35 @@ def chat_about_flowchart(message: str, flow_data: dict | None = None) -> dict:
     """
     settings = get_openrouter_settings()
 
+    try:
+        g_settings = google_ai_service.get_google_settings()
+    except Exception:
+        g_settings = None
+
+    # If OpenRouter is not configured, try Google as a fallback.
     if not settings.api_key:
-        return {
-            "reply": _fallback_response(message, flow_data),
-            "updated_flow": None,
-        }
+        if g_settings and g_settings.api_key:
+            context = ""
+            if flow_data:
+                steps_summary = []
+                for s in flow_data.get("steps", []):
+                    steps_summary.append(
+                        f"- [{s.get('type', 'process')}] {s.get('title', '')}"
+                    )
+                context = (
+                    f"\nCurrent flowchart: {flow_data.get('title', 'Untitled')}\n"
+                    f"Steps:\n" + "\n".join(steps_summary)
+                )
+            try:
+                reply = google_ai_service.call_google_text(
+                    SYSTEM_PROMPT, f"{message}{context}", max_tokens=500, tool_name="flowchart_chat"
+                )
+                return {"reply": reply, "updated_flow": None}
+            except Exception as e:
+                logger.exception("Google AI fallback failed: %s", e)
+                return {"reply": _fallback_response(message, flow_data), "updated_flow": None}
+
+        return {"reply": _fallback_response(message, flow_data), "updated_flow": None}
 
     # Build context
     context = ""
@@ -97,12 +122,30 @@ def chat_about_flowchart(message: str, flow_data: dict | None = None) -> dict:
 
     except requests.exceptions.Timeout:
         logger.warning("OpenRouter API timeout")
+        # Try Google fallback on timeout
+        if g_settings and g_settings.api_key:
+            try:
+                reply = google_ai_service.call_google_text(
+                    SYSTEM_PROMPT, f"{message}{context}", max_tokens=500, tool_name="flowchart_chat"
+                )
+                return {"reply": reply, "updated_flow": None}
+            except Exception as e:
+                logger.exception("Google fallback failed after OpenRouter timeout: %s", e)
         return {
             "reply": "The AI service is taking too long. Please try again.",
             "updated_flow": None,
         }
     except Exception as e:
         logger.error(f"OpenRouter API error: {e}")
+        # Try Google as a fallback on generic errors
+        if g_settings and g_settings.api_key:
+            try:
+                reply = google_ai_service.call_google_text(
+                    SYSTEM_PROMPT, f"{message}{context}", max_tokens=500, tool_name="flowchart_chat"
+                )
+                return {"reply": reply, "updated_flow": None}
+            except Exception as ge:
+                logger.exception("Google fallback failed: %s", ge)
         return {
             "reply": _fallback_response(message, flow_data),
             "updated_flow": None,

backend/app/services/google_ai_service.py

@@ -0,0 +1,172 @@
+"""Google Generative AI integration wrapper.
+
+This module provides a thin wrapper that attempts to use the installed
+`google-generativeai` package if available and falls back to a best-effort
+REST call to the Generative Language endpoints. The wrapper keeps a simple
+`call_google_text` interface that returns a generated string or raises an
+exception on failure.
+"""
+from dataclasses import dataclass
+import logging
+import os
+from typing import Any
+
+import requests
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass(frozen=True)
+class GoogleSettings:
+    api_key: str
+    model: str
+
+
+def get_google_settings() -> GoogleSettings:
+    api_key = str(os.getenv("GOOGLE_API_KEY", "")).strip()
+    model = str(os.getenv("GOOGLE_MODEL", "chat-bison-001")).strip() or "chat-bison-001"
+    return GoogleSettings(api_key=api_key, model=model)
+
+
+def _extract_text_from_google_response(resp: Any) -> str:
+    try:
+        if resp is None:
+            return ""
+
+        # dict-style responses
+        if isinstance(resp, dict):
+            # common shape: {"candidates": [{"output": "..."}]}
+            candidates = resp.get("candidates") or resp.get("choices")
+            if isinstance(candidates, list) and candidates:
+                first = candidates[0]
+                if isinstance(first, dict):
+                    for key in ("output", "text", "message", "content"):
+                        val = first.get(key)
+                        if isinstance(val, str) and val.strip():
+                            return val.strip()
+                    # nested content
+                    content = first.get("content")
+                    if isinstance(content, dict):
+                        for k in ("text", "parts", "output"):
+                            v = content.get(k)
+                            if isinstance(v, str) and v.strip():
+                                return v.strip()
+
+            # look for top-level text-like fields
+            for key in ("output", "text", "response", "message"):
+                val = resp.get(key)
+                if isinstance(val, str) and val.strip():
+                    return val.strip()
+
+            return str(resp)
+
+        # object-like responses (SDK objects)
+        if hasattr(resp, "candidates"):
+            try:
+                c0 = resp.candidates[0]
+                if hasattr(c0, "output"):
+                    return getattr(c0, "output", "") or ""
+                if hasattr(c0, "content"):
+                    return getattr(c0, "content", "") or ""
+            except Exception:
+                pass
+
+        if hasattr(resp, "output"):
+            return getattr(resp, "output", "") or ""
+
+        return str(resp)
+    except Exception:
+        return ""
+
+
+def _call_google_via_rest(settings: GoogleSettings, system_prompt: str, user_message: str, max_tokens: int) -> str:
+    # Try a few likely endpoint patterns for the Google Generative Language API.
+    candidate_urls = [
+        f"https://generativelanguage.googleapis.com/v1/models/{settings.model}:generateText",
+        f"https://generativelanguage.googleapis.com/v1beta2/models/{settings.model}:generateText",
+        f"https://generativelanguage.googleapis.com/v1/models/{settings.model}:generateMessage",
+        f"https://generativelanguage.googleapis.com/v1beta2/models/{settings.model}:generateMessage",
+    ]
+
+    payload_variants = [
+        {
+            "prompt": {"messages": [{"author": "system", "content": system_prompt}, {"author": "user", "content": user_message}]},
+            "temperature": 0.5,
+            "maxOutputTokens": max_tokens,
+        },
+        {
+            "input": f"{system_prompt}\n\n{user_message}",
+            "temperature": 0.5,
+            "maxOutputTokens": max_tokens,
+        },
+        {"prompt": f"{system_prompt}\n\n{user_message}", "temperature": 0.5, "maxOutputTokens": max_tokens},
+    ]
+
+    headers = {"Content-Type": "application/json"}
+
+    for url in candidate_urls:
+        for payload in payload_variants:
+            try:
+                resp = requests.post(url, params={"key": settings.api_key}, json=payload, headers=headers, timeout=60)
+            except requests.exceptions.RequestException as e:
+                logger.debug("Google REST call to %s failed: %s", url, e)
+                continue
+
+            if resp.status_code == 200:
+                try:
+                    data = resp.json()
+                    text = _extract_text_from_google_response(data)
+                    if text:
+                        return text
+                except Exception:
+                    continue
+
+            if resp.status_code == 401:
+                raise RuntimeError("GOOGLE_UNAUTHORIZED")
+
+            if resp.status_code in (429, 502, 503, 504):
+                # transient problem
+                raise RuntimeError("GOOGLE_RATE_LIMIT_OR_SERVER_ERROR")
+
+    raise RuntimeError("GOOGLE_REQUEST_FAILED")
+
+
+def call_google_text(system_prompt: str, user_message: str, max_tokens: int = 1000, tool_name: str = "pdf_ai") -> str:
+    settings = get_google_settings()
+    if not settings.api_key:
+        raise RuntimeError("GOOGLE_MISSING_API_KEY")
+
+    try:
+        import google.generativeai as genai
+
+        # configure SDK if it exposes configure
+        try:
+            if hasattr(genai, "configure"):
+                genai.configure(api_key=settings.api_key)
+        except Exception:
+            logger.debug("google.generativeai.configure failed or not available")
+
+        messages = [{"role": "system", "content": system_prompt}, {"role": "user", "content": user_message}]
+
+        # Try chat-style API if available
+        if hasattr(genai, "chat") and hasattr(genai.chat, "create"):
+            resp = genai.chat.create(model=settings.model, messages=messages, temperature=0.5, max_output_tokens=max_tokens)
+            text = _extract_text_from_google_response(resp)
+            if not text:
+                raise RuntimeError("GOOGLE_EMPTY_RESPONSE")
+            return text
+
+        # Try generate_text if present
+        if hasattr(genai, "generate_text"):
+            prompt = f"{system_prompt}\n\n{user_message}"
+            resp = genai.generate_text(model=settings.model, prompt=prompt, max_output_tokens=max_tokens, temperature=0.5)
+            text = _extract_text_from_google_response(resp)
+            if not text:
+                raise RuntimeError("GOOGLE_EMPTY_RESPONSE")
+            return text
+
+    except Exception as e:  # fall back to REST approach if SDK call fails
+        logger.debug("google.generativeai SDK not usable or raised: %s", e)
+
+    # Last-resort: try REST endpoints
+    return _call_google_via_rest(settings, system_prompt, user_message, max_tokens)

backend/app/services/pdf_ai_service.py

@@ -13,6 +13,7 @@ from app.services.openrouter_config_service import (
     extract_openrouter_text,
     get_openrouter_settings,
 )
+from app.services import google_ai_service
 
 logger = logging.getLogger(__name__)
 
@@ -373,6 +374,58 @@ def _split_translation_chunks(
     return chunks or [text]
 
 
+def _call_openrouter_translate(
+    chunk: str, target_language: str, source_language: str | None = None
+) -> dict:
+    """Attempt translation via OpenRouter, fall back to Google Generative AI if configured."""
+    source_hint = "auto-detect the source language"
+    if source_language and _normalize_language_code(source_language) != "auto":
+        source_hint = f"treat {_language_label(source_language)} as the source language"
+
+    system_prompt = (
+        "You are a professional document translator. "
+        f"Translate the provided PDF content into {_language_label(target_language)}. "
+        f"Please {source_hint}. Preserve headings, lists, tables, and page markers. "
+        "Return only the translated text."
+    )
+
+    # Try OpenRouter first
+    try:
+        translation = _call_openrouter(
+            system_prompt,
+            chunk,
+            max_tokens=2200,
+            tool_name="pdf_translate_fallback",
+        )
+        provider = "openrouter"
+    except (RetryableTranslationError, PdfAiError) as open_err:
+        # If Google is configured, try as a fallback
+        try:
+            g_settings = google_ai_service.get_google_settings()
+        except Exception:
+            g_settings = None
+
+        if g_settings and g_settings.api_key:
+            try:
+                translation = google_ai_service.call_google_text(
+                    system_prompt, chunk, max_tokens=2200, tool_name="pdf_translate_fallback"
+                )
+                provider = "google"
+            except Exception as google_err:
+                logger.exception("Google fallback for translation failed: %s", google_err)
+                raise open_err
+        else:
+            raise open_err
+
+    return {
+        "translation": translation,
+        "provider": provider,
+        "detected_source_language": _normalize_language_code(
+            source_language, default=""
+        ),
+    }
+
+
 def _call_deepl_translate(
     chunk: str, target_language: str, source_language: str | None = None
 ) -> dict:
@@ -593,9 +646,26 @@ def chat_with_pdf(input_path: str, question: str) -> dict:
     )
 
     user_msg = f"Document content:\n{truncated}\n\nQuestion: {question}"
-    reply = _call_openrouter(
-        system_prompt, user_msg, max_tokens=800, tool_name="pdf_chat"
-    )
+    try:
+        reply = _call_openrouter(
+            system_prompt, user_msg, max_tokens=800, tool_name="pdf_chat"
+        )
+    except (RetryableTranslationError, PdfAiError) as open_err:
+        try:
+            g_settings = google_ai_service.get_google_settings()
+        except Exception:
+            g_settings = None
+
+        if g_settings and g_settings.api_key:
+            try:
+                reply = google_ai_service.call_google_text(
+                    system_prompt, user_msg, max_tokens=800, tool_name="pdf_chat"
+                )
+            except Exception as google_err:
+                logger.exception("Google fallback for pdf chat failed: %s", google_err)
+                raise open_err
+        else:
+            raise open_err
 
     page_count = text.count("[Page ")
     return {"reply": reply, "pages_analyzed": page_count}
@@ -637,9 +707,26 @@ def summarize_pdf(input_path: str, length: str = "medium") -> dict:
     )
 
     user_msg = f"{length_instruction}\n\nDocument content:\n{truncated}"
-    summary = _call_openrouter(
-        system_prompt, user_msg, max_tokens=1000, tool_name="pdf_summarize"
-    )
+    try:
+        summary = _call_openrouter(
+            system_prompt, user_msg, max_tokens=1000, tool_name="pdf_summarize"
+        )
+    except (RetryableTranslationError, PdfAiError) as open_err:
+        try:
+            g_settings = google_ai_service.get_google_settings()
+        except Exception:
+            g_settings = None
+
+        if g_settings and g_settings.api_key:
+            try:
+                summary = google_ai_service.call_google_text(
+                    system_prompt, user_msg, max_tokens=1000, tool_name="pdf_summarize"
+                )
+            except Exception as google_err:
+                logger.exception("Google fallback for pdf summarize failed: %s", google_err)
+                raise open_err
+        else:
+            raise open_err
 
     page_count = text.count("[Page ")
     return {"summary": summary, "pages_analyzed": page_count}