import { writeFileSync } from "node:fs";
import { stat } from "node:fs/promises";
import { tmpdir } from "node:os";
import { join } from "node:path";
import { afterEach, beforeAll, describe, expect, it, vi } from "vitest";
import type { SessionHeader } from "../src/core/session-manager.js";
import { SessionManager } from "../src/core/session-manager.js";
import { initTheme } from "../src/modes/interactive/theme/theme.js";

function createSessionFile(path: string): void {
  const header: SessionHeader = {
    type: "session",
    id: "test-session",
    version: 3,
    timestamp: new Date(0).toISOString(),
    cwd: "/tmp",
  };
  writeFileSync(path, `${JSON.stringify(header)}\n`, "utf8");

  // SessionManager only persists once it has seen at least one assistant message.
  // Add a minimal assistant entry so subsequent appends are persisted.
  const mgr = SessionManager.open(path);
  mgr.appendMessage({
    role: "assistant",
    content: [{ type: "text", text: "hi" }],
    api: "openai-completions",
    provider: "openai",
    model: "test",
    usage: {
      input: 1,
      output: 1,
      cacheRead: 0,
      cacheWrite: 0,
      totalTokens: 2,
      cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
    },
    stopReason: "stop",
    timestamp: Date.now(),
  });
}

describe("SessionInfo.modified", () => {
  beforeAll(() => initTheme("dark"));

  afterEach(() => {
    vi.restoreAllMocks();
  });

  it("uses last user/assistant message timestamp instead of file mtime", async () => {
    const filePath = join(tmpdir(), `companion-session-${Date.now()}-modified.jsonl`);
    createSessionFile(filePath);

    const before = await stat(filePath);
    // Ensure the file mtime can differ from our message timestamp even on coarse filesystems.
    await new Promise((r) => setTimeout(r, 10));

    const mgr = SessionManager.open(filePath);
    const msgTime = Date.now();
    mgr.appendMessage({
      role: "assistant",
      content: [{ type: "text", text: "later" }],
      api: "openai-completions",
      provider: "openai",
      model: "test",
      usage: {
        input: 1,
        output: 1,
        cacheRead: 0,
        cacheWrite: 0,
        totalTokens: 2,
        cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
      },
      stopReason: "stop",
      timestamp: msgTime,
    });

    const sessions = await SessionManager.list(
      "/tmp",
      filePath.replace(/\/[^/]+$/, ""),
    );
    const s = sessions.find((x) => x.path === filePath);
    expect(s).toBeDefined();
    expect(s!.modified.getTime()).toBe(msgTime);
    expect(s!.modified.getTime()).not.toBe(before.mtime.getTime());
  });
});