add safety checks and debug logging to period time calculations

This commit adds logging infrastructure and safety checks to prevent time
adjustment overflows in get_period_totals(). Includes early return for empty
results and detailed debug logging for troubleshooting period calculations.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

dmapp/dmweb/get_period_times.py

@@ -1,10 +1,15 @@
 from collections import Counter, defaultdict
 from datetime import datetime, timedelta
 from pprint import pprint
+import logging
 
 from pymongo import MongoClient
 from zoneinfo import ZoneInfo
 
+# Setup logging for debugging
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
 timezone = ZoneInfo("America/Argentina/Buenos_Aires")
 utctz = ZoneInfo("UTC")
 
@@ -266,6 +271,10 @@ def get_period_totals(start, end, task=None):
 
     aux_results = list(switches.aggregate(pipeline_before_after))
 
+    # Safety check: if aux_results is empty, return early with no data
+    if not aux_results:
+        return [{"ws": "No Data", "total": ""}]
+
     bfirst = aux_results[0]["before_first"]
 
     if bfirst:
@@ -279,14 +288,30 @@ def get_period_totals(start, end, task=None):
     rows = []
     active_vs_idle = {"Active": 0, "Idle": 0}
 
+    # Debug logging
+    logger.debug(f"Processing results for period {start} to {end}")
+    logger.debug(f"bfirst workspace: {bfirst['workspace'] if bfirst else 'None'}")
+    logger.debug(f"ldoc workspace: {ldoc['workspace']}")
+
     for result in results:
+        original_total = result["total"]
+
         if bfirst:
             if result["_id"] == bfirst["workspace"]:
-                result["total"] -= start_delta
+                # Safety: ensure start_delta doesn't exceed total
+                adjustment = min(start_delta, result["total"])
+                result["total"] -= adjustment
+                logger.debug(f"{result['_id']}: adjusted start by -{adjustment}s (was {original_total}s, now {result['total']}s)")
 
         if end < now():
             if result["_id"] == ldoc["workspace"]:
-                result["total"] -= ldoc["delta"] - end_delta
+                # Safety: ensure we don't subtract more than the total
+                adjustment = ldoc["delta"] - end_delta
+                safe_adjustment = min(adjustment, result["total"])
+                result["total"] -= safe_adjustment
+                logger.debug(f"{result['_id']}: adjusted end by -{safe_adjustment}s (was {original_total}s, now {result['total']}s)")
+
+        logger.debug(f"{result['_id']}: final total = {result['total']}s ({convert_seconds(result['total'])})")
 
     for result in results:
         if result["total"] > 0: