refactor(slack): share system-event ingress and test harness

src/slack/monitor/events/system-event-context.ts

@@ -0,0 +1,44 @@
+import { logVerbose } from "../../../globals.js";
+import { authorizeSlackSystemEventSender } from "../auth.js";
+import { resolveSlackChannelLabel } from "../channel-config.js";
+import type { SlackMonitorContext } from "../context.js";
+
+export type SlackAuthorizedSystemEventContext = {
+  channelLabel: string;
+  sessionKey: string;
+};
+
+export async function authorizeAndResolveSlackSystemEventContext(params: {
+  ctx: SlackMonitorContext;
+  senderId?: string;
+  channelId?: string;
+  channelType?: string | null;
+  eventKind: string;
+}): Promise<SlackAuthorizedSystemEventContext | undefined> {
+  const { ctx, senderId, channelId, channelType, eventKind } = params;
+  const auth = await authorizeSlackSystemEventSender({
+    ctx,
+    senderId,
+    channelId,
+    channelType,
+  });
+  if (!auth.allowed) {
+    logVerbose(
+      `slack: drop ${eventKind} sender ${senderId ?? "unknown"} channel=${channelId ?? "unknown"} reason=${auth.reason ?? "unauthorized"}`,
+    );
+    return undefined;
+  }
+
+  const channelLabel = resolveSlackChannelLabel({
+    channelId,
+    channelName: auth.channelName,
+  });
+  const sessionKey = ctx.resolveSlackSystemEventSessionKey({
+    channelId,
+    channelType: auth.channelType,
+  });
+  return {
+    channelLabel,
+    sessionKey,
+  };
+}