fix: correct subscription validation, byte-based log cap, partial autostart, URL scheme

- diagnostics.py: fix allow-list vs field name mismatch in subscription validator
  (_ALLOWED_SUBSCRIPTION_FIELDS now contains schema field names like "logFile",
  not operation names like "logFileSubscription", matching what _SUBSCRIPTION_NAME_PATTERN
  extracts); add _validate_subscription_query() called before any network I/O;
  replace chained .replace() URL building with build_ws_url(); gate connection_issues
  on current failure state via _analyze_subscription_status()
- manager.py: add _cap_log_content() with byte-count pre-check
  (len(value.encode("utf-8", errors="replace")) > _MAX_RESOURCE_DATA_BYTES) so
  multibyte UTF-8 content cannot bypass the 1 MB cap
- resources.py: add double-checked locking (_startup_lock) in ensure_subscriptions_started();
  propagate exception from auto_start_all_subscriptions() via raise so
  _subscriptions_started=True is never set after a failed init
- utils.py: add build_ws_url() that raises ValueError on unknown/missing URL scheme
  instead of silently falling through; add _analyze_subscription_status() helper
  that gates connection_issues on current failure state

Resolves review threads PRRT_kwDOO6Hdxs50E50Y PRRT_kwDOO6Hdxs50E50a PRRT_kwDOO6Hdxs50E50c PRRT_kwDOO6Hdxs50E50d PRRT_kwDOO6Hdxs50E2iN PRRT_kwDOO6Hdxs50E2h8

unraid_mcp/subscriptions/utils.py

@@ -1,8 +1,79 @@
 """Shared utilities for the subscription system."""
 
 import ssl as _ssl
+from typing import Any
 
-from ..config.settings import UNRAID_VERIFY_SSL
+from ..config.settings import UNRAID_API_URL, UNRAID_VERIFY_SSL
+
+
+def build_ws_url() -> str:
+    """Build a WebSocket URL from the configured UNRAID_API_URL.
+
+    Converts http(s) scheme to ws(s) and ensures /graphql path suffix.
+
+    Returns:
+        The WebSocket URL string (e.g. "wss://10.1.0.2:31337/graphql").
+
+    Raises:
+        ValueError: If UNRAID_API_URL is not configured or has an unrecognised scheme.
+    """
+    if not UNRAID_API_URL:
+        raise ValueError("UNRAID_API_URL is not configured")
+
+    if UNRAID_API_URL.startswith("https://"):
+        ws_url = "wss://" + UNRAID_API_URL[len("https://") :]
+    elif UNRAID_API_URL.startswith("http://"):
+        ws_url = "ws://" + UNRAID_API_URL[len("http://") :]
+    elif UNRAID_API_URL.startswith(("ws://", "wss://")):
+        ws_url = UNRAID_API_URL  # Already a WebSocket URL
+    else:
+        raise ValueError(
+            f"UNRAID_API_URL must start with http://, https://, ws://, or wss://. "
+            f"Got: {UNRAID_API_URL[:20]}..."
+        )
+
+    if not ws_url.endswith("/graphql"):
+        ws_url = ws_url.rstrip("/") + "/graphql"
+
+    return ws_url
+
+
+def _analyze_subscription_status(
+    status: dict[str, Any],
+) -> tuple[int, list[dict[str, Any]]]:
+    """Analyze subscription status dict, returning error count and connection issues.
+
+    Only reports connection_issues for subscriptions that are currently in a
+    failure state (not recovered ones that happen to have a stale last_error).
+
+    Args:
+        status: Dict of subscription name -> status info from get_subscription_status().
+
+    Returns:
+        Tuple of (error_count, connection_issues_list).
+    """
+    _error_states = frozenset(
+        {"error", "auth_failed", "timeout", "max_retries_exceeded", "invalid_uri"}
+    )
+    error_count = 0
+    connection_issues: list[dict[str, Any]] = []
+
+    for sub_name, sub_status in status.items():
+        runtime = sub_status.get("runtime", {})
+        conn_state = runtime.get("connection_state", "unknown")
+        if conn_state in _error_states:
+            error_count += 1
+        # Gate on current failure state so recovered subscriptions are not reported
+        if runtime.get("last_error") and conn_state in _error_states:
+            connection_issues.append(
+                {
+                    "subscription": sub_name,
+                    "state": conn_state,
+                    "error": runtime["last_error"],
+                }
+            )
+
+    return error_count, connection_issues
 
 
 def build_ws_ssl_context(ws_url: str) -> _ssl.SSLContext | None: