Slack: add modal private metadata utilities

src/slack/modal-metadata.test.ts

@@ -0,0 +1,55 @@
+import { describe, expect, it } from "vitest";
+import {
+  encodeSlackModalPrivateMetadata,
+  parseSlackModalPrivateMetadata,
+} from "./modal-metadata.js";
+
+describe("parseSlackModalPrivateMetadata", () => {
+  it("returns empty object for missing or invalid values", () => {
+    expect(parseSlackModalPrivateMetadata(undefined)).toEqual({});
+    expect(parseSlackModalPrivateMetadata("")).toEqual({});
+    expect(parseSlackModalPrivateMetadata("{bad-json")).toEqual({});
+  });
+
+  it("parses known metadata fields", () => {
+    expect(
+      parseSlackModalPrivateMetadata(
+        JSON.stringify({
+          sessionKey: "agent:main:slack:channel:C1",
+          channelId: "D123",
+          channelType: "im",
+          ignored: "x",
+        }),
+      ),
+    ).toEqual({
+      sessionKey: "agent:main:slack:channel:C1",
+      channelId: "D123",
+      channelType: "im",
+    });
+  });
+});
+
+describe("encodeSlackModalPrivateMetadata", () => {
+  it("encodes only known non-empty fields", () => {
+    expect(
+      JSON.parse(
+        encodeSlackModalPrivateMetadata({
+          sessionKey: "agent:main:slack:channel:C1",
+          channelId: "",
+          channelType: "im",
+        }),
+      ),
+    ).toEqual({
+      sessionKey: "agent:main:slack:channel:C1",
+      channelType: "im",
+    });
+  });
+
+  it("throws when encoded payload exceeds Slack metadata limit", () => {
+    expect(() =>
+      encodeSlackModalPrivateMetadata({
+        sessionKey: `agent:main:${"x".repeat(4000)}`,
+      }),
+    ).toThrow(/cannot exceed 3000 chars/i);
+  });
+});