feat: message-per-row transcript, session resume, drop the composer (#4)

src/__tests__/thread.test.ts

@@ -0,0 +1,116 @@
+import { describe, expect, it } from "vitest";
+import { MESSAGE_PREVIEW_LENGTH, buildThread, type LiveState } from "../lib/thread";
+import type { ChatTurn } from "../lib/types";
+
+const idle: LiveState = { isStreaming: false, response: "", thinking: "" };
+
+function turn(id: string, prompt: string, response: string, overrides: Partial<ChatTurn> = {}): ChatTurn {
+  return {
+    id,
+    prompt,
+    response,
+    thinking: "",
+    model: "m",
+    createdAt: 100,
+    toolCalls: [],
+    ...overrides,
+  };
+}
+
+describe("buildThread", () => {
+  it("returns nothing for an empty conversation", () => {
+    expect(buildThread([], idle)).toEqual([]);
+  });
+
+  it("flattens a turn into a user message followed by an assistant message", () => {
+    const thread = buildThread([turn("t1", "hello", "hi there")], idle);
+
+    expect(thread.map((message) => message.role)).toEqual(["user", "assistant"]);
+    expect(thread[0].text).toBe("hello");
+    expect(thread[1].text).toBe("hi there");
+  });
+
+  it("keeps messages in chronological order across turns", () => {
+    const thread = buildThread(
+      [turn("t1", "first question", "first answer"), turn("t2", "second question", "second answer")],
+      idle,
+    );
+
+    expect(thread.map((message) => message.text)).toEqual([
+      "first question",
+      "first answer",
+      "second question",
+      "second answer",
+    ]);
+  });
+
+  it("gives every message a unique id", () => {
+    const thread = buildThread([turn("t1", "a", "b"), turn("t2", "c", "d")], idle);
+    const ids = thread.map((message) => message.id);
+
+    expect(new Set(ids).size).toBe(ids.length);
+  });
+
+  it("builds one-line previews", () => {
+    const thread = buildThread([turn("t1", "hello\n\nworld", "a\nlong\n\nanswer")], idle);
+
+    expect(thread[0].preview).toBe("hello world");
+    expect(thread[1].preview).toBe("a long answer");
+  });
+
+  it("clips a preview longer than the row can show", () => {
+    const long = "x".repeat(MESSAGE_PREVIEW_LENGTH + 50);
+    const thread = buildThread([turn("t1", long, long)], idle);
+
+    expect(thread[0].preview).toHaveLength(MESSAGE_PREVIEW_LENGTH);
+  });
+
+  it("streams the newest turn only", () => {
+    const live: LiveState = { isStreaming: true, response: "streaming now", thinking: "hmm" };
+    const thread = buildThread([turn("t1", "old", "old answer"), turn("t2", "new", "")], live);
+
+    // The older turn stays put...
+    expect(thread[1].isStreaming).toBe(false);
+    expect(thread[1].text).toBe("old answer");
+
+    // ...and the newest assistant message reads from the live buffer.
+    expect(thread[3].isStreaming).toBe(true);
+    expect(thread[3].text).toBe("streaming now");
+    expect(thread[3].thinking).toBe("hmm");
+
+    // The user's line is never "streaming".
+    expect(thread[2].isStreaming).toBe(false);
+  });
+
+  it("falls back to the activity line while an answer has no text yet", () => {
+    const live: LiveState = { isStreaming: true, response: "", thinking: "", status: "Searching the web" };
+    const thread = buildThread([turn("t1", "q", "")], live);
+
+    expect(thread[1].preview).toBe("Searching the web");
+  });
+
+  it("falls back to a generic label while thinking", () => {
+    const live: LiveState = { isStreaming: true, response: "", thinking: "" };
+    const thread = buildThread([turn("t1", "q", "")], live);
+
+    expect(thread[1].preview).toBe("Thinking…");
+  });
+
+  it("previews a stored error when a finished turn has no answer", () => {
+    const thread = buildThread([turn("t1", "q", "", { error: "Request failed" })], idle);
+
+    expect(thread[1].preview).toBe("Request failed");
+    expect(thread[1].error).toBe("Request failed");
+  });
+
+  it("carries tool calls onto the assistant message", () => {
+    const withTools = turn("t1", "q", "a", {
+      toolCalls: [{ name: "web_search", arguments: {}, result: "ok", isError: false }],
+    });
+    const thread = buildThread([withTools], idle);
+
+    expect(thread[0].toolCalls).toEqual([]);
+    expect(thread[1].toolCalls).toHaveLength(1);
+    expect(thread[1].toolCalls[0].name).toBe("web_search");
+  });
+});