feat: prepare ARR for controlled public deployment

arr_mcp/gateway.py

@@ -0,0 +1,45 @@
+"""Framework-neutral adapter for the single ARR MCP tool."""
+
+from __future__ import annotations
+
+import threading
+from typing import Any, Dict, Protocol
+
+from arr_ingestion.contracts import IngestionError
+from arr_ingestion.direct_contracts import DirectSubmissionReceipt
+
+
+class DirectResultSubmitter(Protocol):
+    def submit(self, raw_request: Any) -> DirectSubmissionReceipt:
+        ...
+
+
+class DirectResultGateway:
+    """Expose one bounded command without duplicating ingestion logic."""
+
+    def __init__(
+        self,
+        service: DirectResultSubmitter,
+        *,
+        max_concurrency: int = 2,
+    ) -> None:
+        if (
+            not isinstance(max_concurrency, int)
+            or isinstance(max_concurrency, bool)
+            or not 1 <= max_concurrency <= 8
+        ):
+            raise ValueError("direct gateway concurrency is invalid")
+        self._service = service
+        self._slots = threading.BoundedSemaphore(max_concurrency)
+
+    def submit_processing_result(self, arguments: Any) -> Dict[str, Any]:
+        if not self._slots.acquire(blocking=False):
+            raise IngestionError(
+                "DIRECT_GATEWAY_BUSY",
+                "direct result gateway is busy; retry later",
+                retryable=True,
+            )
+        try:
+            return self._service.submit(arguments).to_dict()
+        finally:
+            self._slots.release()