/**
 * utils.js 单元测试
 * 覆盖所有工具函数
 */

import {
  generateId,
  escapeHTML,
  prefersDark,
  debounce,
  throttle,
  deepMerge,
  isBrowser,
  formatFileSize,
  sleep,
} from '../src/utils.js';

describe('generateId', () => {
  test('返回字符串', () => {
    expect(typeof generateId()).toBe('string');
  });

  test('以 me- 前缀开头', () => {
    expect(generateId()).toMatch(/^me-/);
  });

  test('多次调用产生不同值', () => {
    const ids = new Set();
    for (let i = 0; i < 100; i++) ids.add(generateId());
    expect(ids.size).toBe(100);
  });
});

describe('escapeHTML', () => {
  test('转义 < > &', () => {
    const out = escapeHTML('<a>&b</a>');
    expect(out).toContain('&lt;');
    expect(out).toContain('&gt;');
    expect(out).toContain('&amp;');
    expect(out).not.toContain('<a>');
  });

  test('null/undefined 转空字符串', () => {
    expect(escapeHTML(null)).toBe('');
    expect(escapeHTML(undefined)).toBe('');
  });

  test('数字被转为字符串', () => {
    expect(escapeHTML(123)).toBe('123');
  });

  test('无特殊字符原样返回', () => {
    expect(escapeHTML('hello world')).toBe('hello world');
  });
});

describe('prefersDark', () => {
  test('返回布尔值', () => {
    expect(typeof prefersDark()).toBe('boolean');
  });
});

describe('debounce', () => {
  test('延迟执行', (done) => {
    let called = 0;
    const fn = debounce(() => { called++; }, 50);
    fn();
    expect(called).toBe(0);
    setTimeout(() => {
      expect(called).toBe(1);
      done();
    }, 100);
  });

  test('多次调用只执行最后一次', (done) => {
    let result = 0;
    const fn = debounce((v) => { result = v; }, 50);
    fn(1);
    fn(2);
    fn(3);
    setTimeout(() => {
      expect(result).toBe(3);
      done();
    }, 100);
  });

  test('immediate 模式立即执行', () => {
    let called = 0;
    const fn = debounce(() => { called++; }, 50, true);
    fn();
    expect(called).toBe(1);
  });

  test('保留 this 上下文', (done) => {
    const obj = {
      val: 42,
      getVal: debounce(function () { return this.val; }, 30),
    };
    const p = obj.getVal();
    // immediate=false 时首次不返回，但 this 应正确
    setTimeout(() => {
      expect(typeof p).toBe('undefined'); // debounce 返回的是 undefined（异步执行）
      done();
    }, 60);
  });

  test('传递参数', (done) => {
    let captured = null;
    const fn = debounce((a, b) => { captured = a + b; }, 30);
    fn(1, 2);
    setTimeout(() => {
      expect(captured).toBe(3);
      done();
    }, 60);
  });
});

describe('throttle', () => {
  test('首次立即执行', () => {
    let called = 0;
    const fn = throttle(() => { called++; }, 50);
    fn();
    expect(called).toBe(1);
  });

  test('限流期内不重复执行', () => {
    let called = 0;
    const fn = throttle(() => { called++; }, 50);
    fn();
    fn();
    fn();
    expect(called).toBe(1);
  });

  test('限流期后可再次执行', (done) => {
    let called = 0;
    const fn = throttle(() => { called++; }, 40);
    fn();
    setTimeout(() => {
      fn();
      expect(called).toBe(2);
      done();
    }, 60);
  });

  test('保留 this 与参数', (done) => {
    const obj = {
      n: 10,
      run: throttle(function (x) { this.result = this.n + x; }, 30),
    };
    obj.run(5);
    expect(obj.result).toBe(15);
    done();
  });
});

describe('deepMerge', () => {
  test('浅层合并', () => {
    const out = deepMerge({ a: 1, b: 2 }, { b: 3, c: 4 });
    expect(out).toEqual({ a: 1, b: 3, c: 4 });
  });

  test('深层对象合并', () => {
    const out = deepMerge({ obj: { x: 1, y: 2 } }, { obj: { y: 3, z: 4 } });
    expect(out).toEqual({ obj: { x: 1, y: 3, z: 4 } });
  });

  test('source 覆盖 target 非对象值', () => {
    const out = deepMerge({ a: { x: 1 } }, { a: 'str' });
    expect(out.a).toBe('str');
  });

  test('不修改原始 target', () => {
    const target = { a: { x: 1 } };
    const source = { a: { y: 2 } };
    deepMerge(target, source);
    expect(target.a).toEqual({ x: 1 });
  });

  test('多层嵌套合并', () => {
    const out = deepMerge(
      { a: { b: { c: 1, d: 2 } } },
      { a: { b: { d: 3, e: 4 } } }
    );
    expect(out).toEqual({ a: { b: { c: 1, d: 3, e: 4 } } });
  });
});

describe('isBrowser', () => {
  test('jsdom 环境下返回 true', () => {
    expect(isBrowser()).toBe(true);
  });
});

describe('formatFileSize', () => {
  test('0 返回 0 Bytes', () => {
    expect(formatFileSize(0)).toBe('0 Bytes');
  });

  test('Bytes 档位', () => {
    expect(formatFileSize(512)).toBe('512 Bytes');
  });

  test('KB 档位', () => {
    expect(formatFileSize(1024)).toBe('1 KB');
    expect(formatFileSize(1536)).toBe('1.5 KB');
  });

  test('MB 档位', () => {
    expect(formatFileSize(1048576)).toBe('1 MB');
  });

  test('GB 档位', () => {
    expect(formatFileSize(1073741824)).toBe('1 GB');
  });

  test('小数位数控制', () => {
    expect(formatFileSize(1536, 0)).toBe('2 KB');
    expect(formatFileSize(1536, 3)).toBe('1.5 KB');
  });

  test('负 decimals 当作 0', () => {
    expect(formatFileSize(1536, -1)).toBe('2 KB');
  });
});

describe('sleep', () => {
  test('返回 Promise', () => {
    expect(sleep(10)).toBeInstanceOf(Promise);
  });

  test('延迟后 resolve', (done) => {
    const start = Date.now();
    sleep(50).then(() => {
      const elapsed = Date.now() - start;
      expect(elapsed).toBeGreaterThanOrEqual(40);
      done();
    });
  });

  test('async/await 用法', async () => {
    const start = Date.now();
    await sleep(30);
    expect(Date.now() - start).toBeGreaterThanOrEqual(20);
  });
});