import { describe, expect, it } from 'vitest';
import { positionDisplay } from '../viewer/position';

// UI-02 §5.2 位置计数形态判定（纯数据层）：三种真实回退 + 前瞻 total 形态。
// 组件侧当前传 total=null（公开端点游标分页无总数）；lightbox.spec 覆盖
// loaded / index / preview 三种模式的端到端渲染。
describe('viewer position display fallbacks (UI-02 §5.2)', () => {
  it('shows i / total only when the API provides an accurate total', () => {
    expect(positionDisplay({ index: 11, loaded: 24, total: 248, atEnd: false, solo: false })).toEqual({
      kind: 'total',
      current: 12,
      total: 248,
    });
  });

  it('shows the loaded count while more pages remain and no total exists', () => {
    expect(positionDisplay({ index: 2, loaded: 24, total: null, atEnd: false, solo: false })).toEqual({
      kind: 'loaded',
      count: 24,
    });
  });

  it('shows i / n of the filtered sequence once all pages are loaded', () => {
    expect(positionDisplay({ index: 4, loaded: 30, total: null, atEnd: true, solo: false })).toEqual({
      kind: 'index',
      current: 5,
      total: 30,
    });
  });

  it('never fabricates a position for unpositioned or solo deep-link entries', () => {
    // solo：即使有准确 total，也不知道目标在筛选序列中的自然位置。
    expect(positionDisplay({ index: 24, loaded: 25, total: 248, atEnd: true, solo: true })).toEqual({
      kind: 'preview',
    });
    // 下标未知（-1，防御分支）。
    expect(positionDisplay({ index: -1, loaded: 3, total: null, atEnd: true, solo: false })).toEqual({
      kind: 'preview',
    });
  });
});