fix: print the running tool once, not twice (#17)

src/__tests__/thread.test.ts

@@ -1,9 +1,11 @@
 import { describe, expect, it } from "vitest";
-import { buildThread, type LiveState } from "../lib/thread";
+import { buildThread, describeActivity, type LiveState } from "../lib/thread";
 import type { ChatTurn } from "../lib/types";
 
 const idle: LiveState = { isStreaming: false, response: "", thinking: "" };
 
+const activity = { label: "Reading a page", count: 1 };
+
 function turn(id: string, prompt: string, response: string, overrides: Partial<ChatTurn> = {}): ChatTurn {
   return {
     id,
@@ -133,3 +135,46 @@ describe("buildThread", () => {
     expect(thread[0].error).toBe("Request failed");
   });
 });
+
+describe("carrying the running tool", () => {
+  const live: LiveState = { isStreaming: true, response: "", thinking: "", activity };
+
+  it("puts it on the message being streamed", () => {
+    const thread = buildThread([turn("t1", "q", "a")], live);
+    const assistant = thread.find((message) => message.role === "assistant");
+
+    expect(assistant?.activity).toEqual(activity);
+  });
+
+  it("keeps it off every earlier message", () => {
+    // Only the newest turn can be mid-flight, and an older answer carrying a
+    // "Searching the web" line would be a claim about a finished turn.
+    const thread = buildThread([turn("t1", "q", "a"), turn("t2", "q2", "a2")], live);
+
+    expect(thread.slice(2).every((message) => message.activity === undefined)).toBe(true);
+  });
+
+  it("drops it once the turn is over", () => {
+    const thread = buildThread([turn("t1", "q", "a")], { ...idle, activity });
+
+    expect(thread.every((message) => message.activity === undefined)).toBe(true);
+  });
+
+  it("never puts one on a question", () => {
+    const thread = buildThread([turn("t1", "q", "a")], live);
+
+    expect(thread.find((message) => message.role === "user")?.activity).toBeUndefined();
+  });
+});
+
+describe("describeActivity", () => {
+  it("is just the label for a first call", () => {
+    expect(describeActivity({ label: "Reading a page", count: 1 })).toBe("Reading a page");
+  });
+
+  it("says a repeat is a repeat, because a bare number reads as progress", () => {
+    expect(describeActivity({ label: "Reading a page", count: 3 })).toBe(
+      "Reading a page · the same call again (3)",
+    );
+  });
+});