refactor: extract stream render model and segment-based rendering

2026-03-10 12:56:18 +07:00
parent 483dd7cb6d
commit 15e9569157
11 changed files with 766 additions and 350 deletions
@@ -0,0 +1,88 @@
+import { describe, expect, it } from "vitest";
+import type { StreamItem } from "@/types/stream";
+import { buildAgentStreamRenderModel } from "./agent-stream-render-model";
+
+function createTimestamp(seed: number): Date {
+  return new Date(`2026-01-01T00:00:${seed.toString().padStart(2, "0")}.000Z`);
+}
+
+function userMessage(id: string, seed: number): StreamItem {
+  return {
+    kind: "user_message",
+    id,
+    text: id,
+    timestamp: createTimestamp(seed),
+  };
+}
+
+function assistantMessage(id: string, seed: number): StreamItem {
+  return {
+    kind: "assistant_message",
+    id,
+    text: id,
+    timestamp: createTimestamp(seed),
+  };
+}
+
+describe("buildAgentStreamRenderModel", () => {
+  it("keeps head separate from committed history on desktop web", () => {
+    const tail: StreamItem[] = [];
+    for (let index = 0; index < 60; index += 1) {
+      const seed = index * 2;
+      tail.push(userMessage(`u${index}`, seed + 1));
+      tail.push(assistantMessage(`a${index}`, seed + 2));
+    }
+    const head = [assistantMessage("live-a", 121)];
+
+    const model = buildAgentStreamRenderModel({
+      tail,
+      head,
+      platform: "web",
+      isMobileBreakpoint: false,
+    });
+
+    expect(model.segments.historyVirtualized.length).toBeGreaterThan(0);
+    expect(model.segments.historyMounted.length).toBeGreaterThan(0);
+    expect(model.segments.liveHead.map((item) => item.id)).toEqual(["live-a"]);
+    expect(model.history).not.toContain(head[0]);
+  });
+
+  it("keeps the full committed tail mounted on mobile web", () => {
+    const tail = [userMessage("u1", 1), assistantMessage("a1", 2)];
+    const head = [assistantMessage("live-a", 3)];
+
+    const model = buildAgentStreamRenderModel({
+      tail,
+      head,
+      platform: "web",
+      isMobileBreakpoint: true,
+    });
+
+    expect(model.segments.historyVirtualized).toHaveLength(0);
+    expect(model.segments.historyMounted).toBe(tail);
+    expect(model.segments.liveHead).toBe(head);
+  });
+
+  it("reuses ordered committed history when only the live head changes", () => {
+    const tail = [userMessage("u1", 1), assistantMessage("a1", 2)];
+    const firstHead = [assistantMessage("live-a", 3)];
+    const secondHead = [assistantMessage("live-b", 4)];
+
+    const first = buildAgentStreamRenderModel({
+      tail,
+      head: firstHead,
+      platform: "native",
+      isMobileBreakpoint: false,
+    });
+    const second = buildAgentStreamRenderModel({
+      tail,
+      head: secondHead,
+      platform: "native",
+      isMobileBreakpoint: false,
+    });
+
+    expect(first.history).toBe(second.history);
+    expect(first.segments.historyMounted).toBe(second.segments.historyMounted);
+    expect(second.segments.liveHead.map((item) => item.id)).toEqual(["live-b"]);
+  });
+});