feat: dashboard UI with real-time stats, light/dark mode, session metrics

health.py

@@ -1,10 +1,83 @@
 import json
 import threading
+import time
+from collections import deque
 from datetime import datetime, timezone
 from http.server import HTTPServer, BaseHTTPRequestHandler
 from io import StringIO
 
 
+class SyncSession:
+    def __init__(self):
+        self._lock = threading.Lock()
+        self.start_time = time.time()
+        self.syncs_total = 0
+        self.syncs_failed = 0
+        self.syncs_skipped = 0
+        self.total_added = 0
+        self.total_updated = 0
+        self.total_deleted = 0
+        self.total_duration = 0.0
+        self.total_latency_ms = 0.0
+        self.non_skip_count = 0
+        self.bandwidth_bytes = 0
+        self.bandwidth_saved_bytes = 0
+        self.history = deque(maxlen=50)
+
+    def record(self, ok: bool, duration: float, added: int, updated: int, deleted: int, skipped: bool, ics_latency_ms: float, msg: str, ics_download_size: int = 0) -> None:
+        with self._lock:
+            self.syncs_total += 1
+            ts = time.strftime("%H:%M:%S", time.gmtime())
+            if not ok:
+                self.syncs_failed += 1
+            if skipped:
+                self.syncs_skipped += 1
+            self.total_added += added
+            self.total_updated += updated
+            self.total_deleted += deleted
+            if not skipped:
+                self.non_skip_count += 1
+            self.total_duration += duration
+            self.total_latency_ms += ics_latency_ms
+            if ics_download_size:
+                self.bandwidth_bytes += ics_download_size
+            self.history.append({
+                "time": ts,
+                "ok": ok,
+                "duration": round(duration, 2),
+                "added": added,
+                "updated": updated,
+                "deleted": deleted,
+                "skipped": skipped,
+                "latency_ms": round(ics_latency_ms),
+                "msg": msg,
+            })
+
+    def get_status(self) -> dict:
+        with self._lock:
+            uptime = time.time() - self.start_time
+            avg_dur = round(self.total_duration / self.non_skip_count, 2) if self.non_skip_count > 0 else 0
+            avg_lat = round(self.total_latency_ms / self.non_skip_count) if self.non_skip_count > 0 else 0
+            return {
+                "uptime_sec": round(uptime),
+                "syncs_total": self.syncs_total,
+                "syncs_failed": self.syncs_failed,
+                "syncs_skipped": self.syncs_skipped,
+                "total_added": self.total_added,
+                "total_updated": self.total_updated,
+                "total_deleted": self.total_deleted,
+                "avg_duration": avg_dur,
+                "avg_latency_ms": avg_lat,
+                "bandwidth_bytes": self.bandwidth_bytes,
+                "bandwidth_saved_bytes": self.bandwidth_saved_bytes,
+                "history": list(self.history),
+            }
+
+    def add_saved_bandwidth(self, bytes_saved: int) -> None:
+        with self._lock:
+            self.bandwidth_saved_bytes += bytes_saved
+
+
 class HealthServer:
     def __init__(self, port: int = 8081):
         self.port = port