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

src/__tests__/markdown.test.ts

@@ -1,84 +1,103 @@
 import { describe, expect, it } from "vitest";
 import {
   STREAMING_CURSOR,
-  buildTurnMarkdown,
-  pendingMarkdown,
+  buildThreadMarkdown,
   previewText,
+  quote,
   sessionToPlainText,
 } from "../lib/markdown";
-import type { ChatTurn } from "../lib/types";
+import type { ChatTurn, ThreadMessage } from "../lib/types";
 
-describe("buildTurnMarkdown", () => {
-  it("renders the question as a quote block above the answer", () => {
-    const markdown = buildTurnMarkdown({ prompt: "What is 2+2?", response: "4" });
+function message(overrides: Partial<ThreadMessage> & Pick<ThreadMessage, "role">): ThreadMessage {
+  return {
+    id: "m1",
+    text: "",
+    preview: "",
+    createdAt: 0,
+    isStreaming: false,
+    thinking: "",
+    toolCalls: [],
+    ...overrides,
+  };
+}
 
-    expect(markdown).toContain("> What is 2+2?");
-    expect(markdown.indexOf("> What is 2+2?")).toBeLessThan(markdown.indexOf("4"));
+describe("quote", () => {
+  it("keeps a multi-line message inside one quote block", () => {
+    expect(quote("line one\nline two")).toBe("> line one\n> line two");
+  });
+});
+
+describe("buildThreadMarkdown", () => {
+  it("returns nothing for an empty conversation", () => {
+    expect(buildThreadMarkdown([])).toBe("");
   });
 
-  it("keeps a multi-line question inside the quote block", () => {
-    const markdown = buildTurnMarkdown({ prompt: "line one\nline two", response: "ok" });
+  it("renders a question as a quote and an answer as body text", () => {
+    const markdown = buildThreadMarkdown([
+      message({ role: "user", text: "What is 2+2?" }),
+      message({ role: "assistant", text: "4" }),
+    ]);
 
-    expect(markdown).toContain("> line one\n> line two");
+    expect(markdown).toContain("**You**");
+    expect(markdown).toContain("> What is 2+2?");
+    expect(markdown).toContain("**Lam**");
+    expect(markdown).toContain("4");
+  });
+
+  it("keeps the conversation in order", () => {
+    const markdown = buildThreadMarkdown([
+      message({ id: "a", role: "user", text: "first" }),
+      message({ id: "b", role: "assistant", text: "second" }),
+      message({ id: "c", role: "user", text: "third" }),
+    ]);
+
+    expect(markdown.indexOf("first")).toBeLessThan(markdown.indexOf("second"));
+    expect(markdown.indexOf("second")).toBeLessThan(markdown.indexOf("third"));
   });
 
   it("marks a streaming answer with a cursor", () => {
-    const streaming = buildTurnMarkdown({ prompt: "q", response: "partial", isStreaming: true });
-    const finished = buildTurnMarkdown({ prompt: "q", response: "partial", isStreaming: false });
+    const streaming = buildThreadMarkdown([
+      message({ role: "assistant", text: "partial", isStreaming: true }),
+    ]);
+    const finished = buildThreadMarkdown([message({ role: "assistant", text: "partial" })]);
 
     expect(streaming).toContain(STREAMING_CURSOR);
     expect(finished).not.toContain(STREAMING_CURSOR);
   });
 
-  it("shows a placeholder while an answer is still empty", () => {
-    expect(buildTurnMarkdown({ prompt: "q", response: "", isStreaming: true })).toContain("Thinking");
-    expect(buildTurnMarkdown({ prompt: "q", response: "", isStreaming: false })).toContain("No response");
+  it("shows a placeholder while an answer has no text yet", () => {
+    expect(buildThreadMarkdown([message({ role: "assistant", isStreaming: true })])).toContain("Thinking");
+    expect(buildThreadMarkdown([message({ role: "assistant" })])).toContain("No response");
   });
 
   it("surfaces an error instead of hiding it", () => {
-    const markdown = buildTurnMarkdown({ prompt: "q", response: "", error: "Ollama rejected the API key." });
+    const markdown = buildThreadMarkdown([
+      message({ role: "assistant", error: "Ollama rejected the API key." }),
+    ]);
     expect(markdown).toContain("Ollama rejected the API key.");
   });
 
   it("lists tools that were used, flagging failures", () => {
-    const markdown = buildTurnMarkdown({
-      prompt: "q",
-      response: "a",
-      toolCalls: [
-        { name: "web_search", arguments: {}, result: "ok", isError: false },
-        { name: "web_fetch", arguments: {}, result: "boom", isError: true },
-      ],
-    });
+    const markdown = buildThreadMarkdown([
+      message({
+        role: "assistant",
+        text: "a",
+        toolCalls: [
+          { name: "web_search", arguments: {}, result: "ok", isError: false },
+          { name: "web_fetch", arguments: {}, result: "boom", isError: true },
+        ],
+      }),
+    ]);
 
     expect(markdown).toContain("`web_search`");
     expect(markdown).toContain("`web_fetch` — failed");
   });
 
-  it("omits the reasoning section when there is none", () => {
-    expect(buildTurnMarkdown({ prompt: "q", response: "a" })).not.toContain("Reasoning");
-    expect(buildTurnMarkdown({ prompt: "q", response: "a", thinking: "hmm" })).toContain("Reasoning");
-  });
-
-  it("includes the model and timestamp in the footer", () => {
-    const markdown = buildTurnMarkdown({
-      prompt: "q",
-      response: "a",
-      model: "gpt-oss:120b",
-      createdAt: 1_700_000_000_000,
-    });
-    expect(markdown).toContain("`gpt-oss:120b`");
-  });
-});
-
-describe("pendingMarkdown", () => {
-  it("shows the question with an activity line", () => {
-    const markdown = pendingMarkdown("q", "Searching the web");
-    expect(markdown).toContain("> q");
-    expect(markdown).toContain("_Searching the web…_");
-  });
-
-  it("falls back to a generic line when there is no status", () => {
-    expect(pendingMarkdown("q")).toContain("_Thinking…_");
+  it("only shows a reasoning section when there is reasoning", () => {
+    expect(buildThreadMarkdown([message({ role: "assistant", text: "a" })])).not.toContain("Reasoning");
+    expect(buildThreadMarkdown([message({ role: "assistant", text: "a", thinking: "hmm" })])).toContain(
+      "Reasoning",
+    );
   });
 });
 
@@ -90,6 +109,10 @@ describe("previewText", () => {
   it("clips with an ellipsis", () => {
     expect(previewText("a".repeat(50), 5)).toHaveLength(5);
   });
+
+  it("leaves short text alone", () => {
+    expect(previewText("hi", 40)).toBe("hi");
+  });
 });
 
 describe("sessionToPlainText", () => {
@@ -111,7 +134,8 @@ describe("sessionToPlainText", () => {
   });
 
   it("includes the failure when a turn errored", () => {
-    const text = sessionToPlainText([turn("q", "", "Ollama rejected the API key.")]);
-    expect(text).toContain("Ollama rejected the API key.");
+    expect(sessionToPlainText([turn("q", "", "Ollama rejected the API key.")])).toContain(
+      "Ollama rejected the API key.",
+    );
   });
 });

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");
+  });
+});