fix: add error handling to export_chat function

app.py

@@ -351,34 +351,38 @@ def toggle_system_status() -> tuple[bool, str]:
 
 def export_chat(history: list, format_type: str = "txt") -> str:
     """Export chat history to a file."""
-    if not history:
-        return "No conversation to export."
-
-    import tempfile
-    timestamp = datetime.utcnow().strftime("%Y%m%d_%H%M%S")
-
-    if format_type == "json":
-        filepath = tempfile.gettempdir() / f"cain_chat_{timestamp}.json"
-        export_data = {
-            "session_id": _session_id,
-            "timestamp": datetime.utcnow().isoformat(),
-            "messages": [{"role": "user" if i % 2 == 0 else "assistant", "content": msg}
-                        for pair in history for i, msg in enumerate(pair)]
-        }
-        with open(filepath, "w") as f:
-            json.dump(export_data, f, indent=2)
-    else:  # txt
-        filepath = tempfile.gettempdir() / f"cain_chat_{timestamp}.txt"
-        with open(filepath, "w") as f:
-            f.write(f"Cain Chat Export - Session: {_session_id}\n")
-            f.write(f"Exported: {datetime.utcnow().isoformat()}\n")
-            f.write("=" * 50 + "\n\n")
-            for user_msg, bot_msg in history:
-                f.write(f"User: {user_msg}\n\n")
-                f.write(f"Cain: {bot_msg}\n\n")
-                f.write("-" * 30 + "\n\n")
-
-    return f"✅ Exported to {filepath.name}"
+    try:
+        if not history:
+            return "No conversation to export."
+
+        import tempfile
+        timestamp = datetime.utcnow().strftime("%Y%m%d_%H%M%S")
+
+        if format_type == "json":
+            filepath = tempfile.gettempdir() / f"cain_chat_{timestamp}.json"
+            export_data = {
+                "session_id": _session_id,
+                "timestamp": datetime.utcnow().isoformat(),
+                "messages": [{"role": "user" if i % 2 == 0 else "assistant", "content": msg}
+                            for pair in history for i, msg in enumerate(pair)]
+            }
+            with open(filepath, "w") as f:
+                json.dump(export_data, f, indent=2)
+        else:  # txt
+            filepath = tempfile.gettempdir() / f"cain_chat_{timestamp}.txt"
+            with open(filepath, "w") as f:
+                f.write(f"Cain Chat Export - Session: {_session_id}\n")
+                f.write(f"Exported: {datetime.utcnow().isoformat()}\n")
+                f.write("=" * 50 + "\n\n")
+                for user_msg, bot_msg in history:
+                    f.write(f"User: {user_msg}\n\n")
+                    f.write(f"Cain: {bot_msg}\n\n")
+                    f.write("-" * 30 + "\n\n")
+
+        return f"✅ Exported to {filepath.name}"
+    except Exception as e:
+        logger.error(f"[EXPORT_ERROR] Failed to export chat: {e}")
+        return f"Export failed: {e}"
 
 
 def track_async_task(task: asyncio.Task):