Fix calendar routing and user-local time context (#408)

* fix(chat): add user-local time context

* fix(chat): route calendar follow-up phrasing

* refactor(chat): log tool intent routing reasons

* test(chat): align user time prompt shim

---------

Co-authored-by: Alex Kenley <Alex.Kenley@threatvectorsecurity.com>

routes/calendar_routes.py

@@ -161,26 +161,18 @@ def _ensure_default_calendar(db, owner: str = None) -> CalendarCal:
     return cal
 
 
-# Per-request user UTC offset (in minutes east of UTC). chat_routes sets this
-# from the `X-Tz-Offset` header so naive natural-language times the LLM
-# emits ("today at 9pm") are parsed in the USER's timezone, not the server's
-# clock.  None = unknown, fall back to legacy server-local behavior.
-from contextvars import ContextVar
-_USER_TZ_OFFSET_MIN: ContextVar = ContextVar("user_tz_offset_min", default=None)
-
-
-def set_user_tz_offset(offset_min):
-    """Set the current user's UTC offset for this async context."""
-    try:
-        v = int(offset_min)
-    except (TypeError, ValueError):
-        return
-    _USER_TZ_OFFSET_MIN.set(v)
-
-
-def get_user_tz_offset():
-    """Read the current user's UTC offset (minutes east of UTC), or None."""
-    return _USER_TZ_OFFSET_MIN.get()
+# Per-request user time context. chat_routes sets this from browser timezone
+# headers so natural-language times the LLM emits ("today at 9pm") are parsed
+# in the user's timezone, not the server's clock. None = unknown, fall back to
+# legacy server-local behavior.
+from src.user_time import (
+    get_user_tz_name,
+    get_user_tz_offset,
+    now_user_local,
+    set_user_tz_name,
+    set_user_tz_offset,
+    user_timezone,
+)
 
 
 def parse_due_for_user(s: str) -> str:
@@ -199,6 +191,7 @@ def parse_due_for_user(s: str) -> str:
     """
     from datetime import timezone as _tz, timedelta as _td
     offset = get_user_tz_offset()
+    tz_name = get_user_tz_name()
     s = (s or "").strip()
     if not s:
         return s
@@ -212,11 +205,11 @@ def parse_due_for_user(s: str) -> str:
     except ValueError:
         parsed = None
 
-    if offset is None:
+    if offset is None and not tz_name:
         # No user tz known — preserve legacy behavior (naive server-local).
         return _parse_dt(s).isoformat()
 
-    user_tz = _tz(_td(minutes=offset))
+    user_tz = user_timezone()
 
     # Naive ISO → tag with user tz.
     if parsed is not None and parsed.tzinfo is None:
@@ -224,7 +217,7 @@ def parse_due_for_user(s: str) -> str:
 
     # Natural language — evaluate against user's "now".
     server_now_utc = datetime.now(_tz.utc)
-    user_now = server_now_utc.astimezone(user_tz)
+    user_now = now_user_local(server_now_utc)
     # Patch datetime.now() inside _parse_dt by leveraging the user's clock:
     # we re-implement the small natural-language phrases here against user_now
     # so the result is naturally in the user's tz.
@@ -232,6 +225,7 @@ def parse_due_for_user(s: str) -> str:
     lower = s.lower().strip()
 
     def _parse_time(t):
+        t = _re.sub(r'\b([ap])\s*\.?\s*m\.?\b', r'\1m', t.strip(), flags=_re.IGNORECASE)
         m = _re.match(r'^\s*(\d{1,2})(?::(\d{2}))?\s*(am|pm)?\s*$', t, _re.IGNORECASE)
         if not m: return None
         h = int(m.group(1)); mn = int(m.group(2) or 0); ampm = (m.group(3) or "").lower()
@@ -341,6 +335,7 @@ def _parse_dt(s: str) -> datetime:
 
     def _parse_time(t: str):
         """Return (hour, minute) from '1pm', '1:30 PM', '13:00', etc., or None."""
+        t = _re.sub(r'\b([ap])\s*\.?\s*m\.?\b', r'\1m', t.strip(), flags=_re.IGNORECASE)
         m = _re.match(r'^\s*(\d{1,2})(?::(\d{2}))?\s*(am|pm)?\s*$', t, _re.IGNORECASE)
         if not m:
             return None
@@ -1210,7 +1205,20 @@ def setup_calendar_routes() -> APIRouter:
         text = (body.get("text") or "").strip()
         if not text:
             raise HTTPException(400, "text is required")
+        from src.user_time import (
+            clear_user_time_context,
+            current_datetime_prompt,
+            now_user_local,
+            set_user_tz_name,
+            set_user_tz_offset,
+        )
+
+        clear_user_time_context()
         tz_hint = (body.get("tz") or "").strip()
+        if body.get("tz_offset") is not None:
+            set_user_tz_offset(body.get("tz_offset"))
+        if tz_hint:
+            set_user_tz_name(tz_hint)
 
         url, model, headers = resolve_endpoint("utility")
         if not url:
@@ -1218,15 +1226,15 @@ def setup_calendar_routes() -> APIRouter:
         if not url or not model:
             return {"ok": False, "error": "No LLM endpoint configured"}
 
-        now = datetime.now()
+        now = now_user_local()
         now_iso = now.strftime("%Y-%m-%dT%H:%M:%S")
         # The model gets only the schema it needs to fill out; we re-validate
         # everything client-side too.
         system_prompt = (
-            "You are a calendar event parser. Read the user's one-line "
+            current_datetime_prompt()
+            + "You are a calendar event parser. Read the user's one-line "
             "description and emit STRICT JSON describing the event. "
-            f"Today is {now.strftime('%A, %Y-%m-%d')} ({now_iso}). "
-            + (f"User timezone: {tz_hint}. " if tz_hint else "")
+            f"The current user-local timestamp is {now_iso}. "
             + "Resolve relative dates (\"tomorrow\", \"friday\", \"next monday\", "
               "\"in 30 minutes\") against today. Default duration is 60 minutes "
               "when no end time is given. If the text mentions a date with no "