1 files changed, 57 insertions, 0 deletions
diff --git a/packages/meshbay-node/src/meshbay_node/ops/core.py b/packages/meshbay-node/src/meshbay_node/ops/core.py
new file mode 100644
index 0000000..7c19d78
--- /dev/null
+++ b/packages/meshbay-node/src/meshbay_node/ops/core.py
@@ -0,0 +1,57 @@
+"""What every operation shares: the refusal it raises and the lookups into `state`."""
+
+from __future__ import annotations
+
+from typing import Any
+
+
+class OpError(Exception):
+    """
+    An operation refused, with enough for any adapter to report it.
+
+    `status` is an HTTP code because one adapter needs one; the others ignore it.
+    `extra` carries the "here is what would have worked" payload — a bare "no
+    such group" leaves an operator guessing at a UUID.
+    """
+
+    def __init__(self, message: str, *, status: int = 400,
+                 extra: dict[str, Any] | None = None):
+        super().__init__(message)
+        self.message = message
+        self.status = status
+        self.extra = extra or {}
+
+    def as_dict(self) -> dict:
+        return {"error": self.message, **self.extra}
+
+
+# ── Shared lookups ───────────────────────────────────────────────────────────
+
+def _roster(state: dict):
+    roster = state.get("roster")
+    if not roster:
+        raise OpError("Roster not available", status=503)
+    return roster
+
+
+def _hub(state: dict):
+    hub = state.get("hub")
+    if not hub or not hub._session:
+        raise OpError("Hub not connected", status=503)
+    return hub
+
+
+def _group_ctx(state: dict, group_id: str) -> dict:
+    groups_ctx = state.get("groups_ctx", {})
+    if group_id not in groups_ctx:
+        raise OpError("Group not hosted on this node", status=404,
+                      extra={"available": [
+                          {"id": gid} for gid in groups_ctx]})
+    return groups_ctx[group_id]
+
+
+def _config(state: dict):
+    config = state.get("config")
+    if not config:
+        raise OpError("No config loaded", status=503)
+    return config