/**
 * chapter-nav 单元测试
 *
 * 覆盖：
 *   1. 第一个章节：无 prev，next 为第二节
 *   2. 中间章节：prev/next 都有
 *   3. 最后一章：有 prev，无 next
 *   4. 章节不在列表中：返 0/nav 全部 null
 *   5. bookId=0 边界
 *   6. DB 异常：返回零值 nav，不抛
 */
import { describe, it, expect, vi, beforeEach } from 'vitest';

const mocks = vi.hoisted(() => ({
  findMany: vi.fn(),
}));

vi.mock('@/models', () => ({
  prisma: {
    bookChapter: {
      findMany: mocks.findMany,
    },
  },
}));

import { getChapterNav } from '@/modules/book-generator/chapter-nav';

describe('chapter-nav', () => {
  beforeEach(() => {
    vi.clearAllMocks();
  });

  it('第一章：prev=null, next=2', async () => {
    mocks.findMany.mockResolvedValue([{ id: 100 }, { id: 101 }, { id: 102 }]);
    const nav = await getChapterNav(1, 100);
    expect(nav.chapter_index).toBe(1);
    expect(nav.total_chapters).toBe(3);
    expect(nav.prev_chapter_id).toBeNull();
    expect(nav.next_chapter_id).toBe(101);
  });

  it('中间章：prev/next 都有', async () => {
    mocks.findMany.mockResolvedValue([{ id: 100 }, { id: 101 }, { id: 102 }]);
    const nav = await getChapterNav(1, 101);
    expect(nav.chapter_index).toBe(2);
    expect(nav.prev_chapter_id).toBe(100);
    expect(nav.next_chapter_id).toBe(102);
  });

  it('最后一章：next=null', async () => {
    mocks.findMany.mockResolvedValue([{ id: 100 }, { id: 101 }, { id: 102 }]);
    const nav = await getChapterNav(1, 102);
    expect(nav.chapter_index).toBe(3);
    expect(nav.prev_chapter_id).toBe(101);
    expect(nav.next_chapter_id).toBeNull();
  });

  it('章节不在列表中：全部 nav null', async () => {
    mocks.findMany.mockResolvedValue([{ id: 100 }, { id: 101 }]);
    const nav = await getChapterNav(1, 999);
    expect(nav.chapter_index).toBe(0);
    expect(nav.total_chapters).toBe(2);
    expect(nav.prev_chapter_id).toBeNull();
    expect(nav.next_chapter_id).toBeNull();
  });

  it('bookId/chapterId 非法：返零值', async () => {
    const nav1 = await getChapterNav(0, 100);
    expect(nav1).toEqual({ chapter_index: 0, total_chapters: 0, prev_chapter_id: null, next_chapter_id: null });
    const nav2 = await getChapterNav(1, 0);
    expect(nav2).toEqual({ chapter_index: 0, total_chapters: 0, prev_chapter_id: null, next_chapter_id: null });
  });

  it('DB 异常：返回零值 nav，不抛', async () => {
    mocks.findMany.mockRejectedValue(new Error('DB down'));
    const nav = await getChapterNav(1, 100);
    expect(nav).toEqual({ chapter_index: 0, total_chapters: 0, prev_chapter_id: null, next_chapter_id: null });
  });
});