refactor: extract shared memory service

surfsense_backend/app/services/memory/rewrite.py

@@ -0,0 +1,35 @@
+"""LLM-backed memory rewrite helpers."""
+
+from __future__ import annotations
+
+import logging
+from typing import Any
+
+from langchain_core.messages import HumanMessage
+
+from app.services.memory.prompts import FORCED_REWRITE_PROMPT
+from app.services.memory.validation import MEMORY_HARD_LIMIT
+from app.utils.content_utils import extract_text_content
+
+logger = logging.getLogger(__name__)
+
+
+async def forced_rewrite(content: str, llm: Any) -> str | None:
+    """Use a focused LLM call to compress memory under the hard limit."""
+    try:
+        prompt = FORCED_REWRITE_PROMPT.format(
+            target=MEMORY_HARD_LIMIT,
+            content=content,
+        )
+        response = await llm.ainvoke(
+            [HumanMessage(content=prompt)],
+            config={"tags": ["surfsense:internal", "memory-rewrite"]},
+        )
+        text = extract_text_content(response.content).strip()
+        if not text:
+            logger.warning("Forced memory rewrite returned empty text")
+            return None
+        return text
+    except Exception:
+        logger.exception("Forced memory rewrite LLM call failed")
+        return None