refactor: split gateway server helpers and tests

src/gateway/session-utils.test.ts

@@ -0,0 +1,34 @@
+import { describe, expect, test } from "vitest";
+import type { SessionEntry } from "../config/sessions.js";
+import {
+  capArrayByJsonBytes,
+  classifySessionKey,
+  parseGroupKey,
+} from "./session-utils.js";
+
+describe("gateway session utils", () => {
+  test("capArrayByJsonBytes trims from the front", () => {
+    const res = capArrayByJsonBytes(["a", "b", "c"], 10);
+    expect(res.items).toEqual(["b", "c"]);
+  });
+
+  test("parseGroupKey handles group prefixes", () => {
+    expect(parseGroupKey("group:abc")).toEqual({ id: "abc" });
+    expect(parseGroupKey("discord:group:dev")).toEqual({
+      surface: "discord",
+      kind: "group",
+      id: "dev",
+    });
+    expect(parseGroupKey("foo:bar")).toBeNull();
+  });
+
+  test("classifySessionKey respects chat type + prefixes", () => {
+    expect(classifySessionKey("global")).toBe("global");
+    expect(classifySessionKey("unknown")).toBe("unknown");
+    expect(classifySessionKey("group:abc")).toBe("group");
+    expect(classifySessionKey("discord:group:dev")).toBe("group");
+    expect(classifySessionKey("main")).toBe("direct");
+    const entry = { chatType: "group" } as SessionEntry;
+    expect(classifySessionKey("main", entry)).toBe("group");
+  });
+});