/**
 * 故障注入基座自测（v0.8.0 工作流 C-1）
 *
 * 这些测试的作用不是测产品代码，而是**证明测试基座本身是有效的**：
 * 如果故障注入不能稳定复现"崩溃丢数据"，那么后面所有崩溃相关测试都是空头支票。
 */

import { TransactionalFileStore, installOPFSMock, clearRegistry, CrashableStoreBackend } from './storage-harness';
import { FaultyBackend } from './faulty-backend';
import { OPFSBackend } from '../../src/engine/aria/store/opfs_backend';
import { decode as decodeBytes } from './assertions';

describe('[v0.8.0] 测试基座：TransactionalFileStore', () => {
  let store: TransactionalFileStore;

  beforeEach(() => {
    clearRegistry();
    store = new TransactionalFileStore({ dbName: 'unit' });
  });

  test('提交语义：未提交的写入对读不可见（真实 OPFS 是 close 才原子替换）', async () => {
    await store.write('k', new TextEncoder().encode('v1').buffer as ArrayBuffer);
    expect(await store.read('k')).toBeNull(); // 未 commit → 读不到
    store.commitAll();
    expect(decodeBytes(await store.read('k'))).toBe('v1');
  });

  test('崩溃语义：丢弃未提交写入，已提交内容保持', async () => {
    await store.write('k', new TextEncoder().encode('committed').buffer as ArrayBuffer);
    store.commitAll();

    await store.write('k', new TextEncoder().encode('pending').buffer as ArrayBuffer);
    expect(store.hasPending()).toBe(true);
    store.crashPending(); // 崩溃：丢掉 pending

    expect(decodeBytes(await store.read('k'))).toBe('committed');
    expect(store.hasPending()).toBe(false);
  });

  test('读返回副本：调用方原地修改不会污染"磁盘"（旧 mock 的缺陷 1）', async () => {
    await store.write('k', new TextEncoder().encode('original').buffer as ArrayBuffer);
    store.commitAll();

    const first = await store.read('k');
    new Uint8Array(first!)[0] = 0x58; // 'X'

    const second = await store.read('k');
    expect(decodeBytes(second)).toBe('original');
  });

  test('故障注入：failNextWrite / failNextAppend / failNextDelete 精确计数', async () => {
    store.failNextWrite();
    await expect(store.write('k', new ArrayBuffer(4))).rejects.toThrow(/injected write failure/);
    await expect(store.write('k', new ArrayBuffer(4))).resolves.toBeUndefined();

    store.failNextAppend(2);
    await expect(store.append('k', new ArrayBuffer(2))).rejects.toThrow(/injected append failure/);
    await expect(store.append('k', new ArrayBuffer(2))).rejects.toThrow(/injected append failure/);
    await expect(store.append('k', new ArrayBuffer(2))).resolves.toBeUndefined();

    store.failNextDelete();
    await expect(store.delete('k')).rejects.toThrow(/injected delete failure/);
  });

  test('撕裂写：truncateNextAppendTo 只落前 n 字节', async () => {
    const text = new TextEncoder();
    await store.write('log', text.encode('AAAA').buffer as ArrayBuffer);
    store.commitAll();

    store.truncateNextAppendTo(2);
    await store.append('log', text.encode('BBBB').buffer as ArrayBuffer);
    store.commitAll();

    // 已提交的 'AAAA' 保留 + 撕裂后只追加了 'BB' → 'AAAABB'
    expect(decodeBytes(await store.read('log'))).toBe('AAAABB');
  });

  test('篡改已提交字节：corruptCommitted 用于 bit-flip 场景', async () => {
    await store.write('k', new TextEncoder().encode('hello').buffer as ArrayBuffer);
    store.commitAll();

    const ok = store.corruptCommitted('k', (bytes) => { bytes[0] ^= 0xff; });
    expect(ok).toBe(true);
    const after = new Uint8Array((await store.read('k'))!);
    expect(after[0]).not.toBe('h'.charCodeAt(0));
  });

  test('提交原子性：commitAll 一次性生效全部 pending', async () => {
    await store.write('a', new ArrayBuffer(1));
    await store.write('b', new ArrayBuffer(1));
    expect(await store.listKeys()).toEqual(['a', 'b']);
    store.commitAll();
    expect((await store.listKeys()).sort()).toEqual(['a', 'b']);
  });
});

describe('[v0.8.0] 测试基座：installOPFSMock 真实语义', () => {
  beforeEach(() => clearRegistry());

  test('keepExistingData:false 会截断（旧 mock 的缺陷 2）', async () => {
    installOPFSMock('trunc');
    const backend = new OPFSBackend();
    await backend.open('trunc');
    await backend.write('f', new TextEncoder().encode('LONGCONTENT').buffer as ArrayBuffer);

    // 覆盖写更短内容 → 真实 OPFS 应截断为 5 字节
    await backend.write('f', new TextEncoder().encode('short').buffer as ArrayBuffer);
    const read = await backend.read('f');
    expect(decodeBytes(read)).toBe('short');
  });

  test('append 是真追加且不破坏已有内容', async () => {
    installOPFSMock('app');
    const backend = new OPFSBackend();
    await backend.open('app');
    await backend.write('log', new TextEncoder().encode('AAA').buffer as ArrayBuffer);
    await backend.append('log', new TextEncoder().encode('BBB').buffer as ArrayBuffer);
    expect(decodeBytes(await backend.read('log'))).toBe('AAABBB');
  });

  test('读返回副本，跨 backend 实例隔离', async () => {
    installOPFSMock('iso');
    const b1 = new OPFSBackend();
    await b1.open('iso');
    await b1.write('k', new TextEncoder().encode('v').buffer as ArrayBuffer);

    const b2 = new OPFSBackend();
    await b2.open('iso');
    const buf = await b2.read('k');
    new Uint8Array(buf!)[0] = 0x5a;

    expect(decodeBytes(await b1.read('k'))).toBe('v');
  });

  test('崩溃后重开：已提交数据在，未提交的不在', async () => {
    const installed = installOPFSMock('crash');
    const store = installed.store;
    store.restoreCommitted(new Map()); // 清空

    await store.write('committed', new TextEncoder().encode('yes').buffer as ArrayBuffer);
    store.commitAll();
    await store.write('pending', new TextEncoder().encode('no').buffer as ArrayBuffer);
    store.crashPending();

    expect(decodeBytes(await store.read('committed'))).toBe('yes');
    expect(await store.read('pending')).toBeNull();
  });
});

describe('[v0.8.0] 测试基座：FaultyBackend', () => {
  beforeEach(() => clearRegistry());

  test('注入的写失败必须真的让调用方拿到 rejection', async () => {
    installOPFSMock('faulty');
    const faulty = new FaultyBackend(new OPFSBackend());
    await faulty.open('faulty');

    faulty.failNextWrite();
    await expect(faulty.write('k', new ArrayBuffer(4))).rejects.toThrow(/injected write failure/);
    expect(faulty.injected.write).toBe(1);

    faulty.clearFaults();
    await expect(faulty.write('k', new ArrayBuffer(4))).resolves.toBeUndefined();
  });

  test('静默丢弃写：调用方看到成功，但介质上没有（掉电场景）', async () => {
    installOPFSMock('drop');
    const faulty = new FaultyBackend(new OPFSBackend());
    await faulty.open('drop');

    faulty.dropNextWrite();
    await expect(faulty.write('k', new ArrayBuffer(4))).resolves.toBeUndefined();
    expect(await faulty.read('k')).toBeNull(); // 静默丢失
    expect(faulty.injected.dropped).toBe(1);
  });

  test('撕裂追加：写到一半的 WAL 记录可被构造', async () => {
    installOPFSMock('torn');
    const faulty = new FaultyBackend(new OPFSBackend());
    await faulty.open('torn');

    const record = new Uint8Array(100).fill(7);
    faulty.truncateNextAppendTo(37);
    await faulty.append('__wal_000000.bin', record.buffer as ArrayBuffer);

    const stored = await faulty.read('__wal_000000.bin');
    expect(stored!.byteLength).toBe(37);
    expect(faulty.injected.truncated).toBe(1);
  });

  test('crash() 丢弃未提交写（这才是崩溃，不是 close 优雅停机）', async () => {
    const store = new TransactionalFileStore({ dbName: 'crash2' });
    const backend = new CrashableStoreBackend(store);
    const faulty = new FaultyBackend(backend);

    const text = new TextEncoder();
    await faulty.write('saved', text.encode('KEEP').buffer as ArrayBuffer);
    backend.commit(); // 模拟 createWritable.close() 完成

    await faulty.write('unsaved', text.encode('LOST').buffer as ArrayBuffer);
    expect(store.hasPending()).toBe(true); // 存在真实的"提交前崩溃窗口"

    expect(faulty.crash()).toBe(true);

    expect(store.hasPending()).toBe(false);
    expect(await store.read('unsaved')).toBeNull();
    expect(decodeBytes(await store.read('saved'))).toBe('KEEP');
  });

  test('对照组：close() 是优雅停机，会把未提交写刷完 —— 因此不能用来模拟崩溃', async () => {
    const store = new TransactionalFileStore({ dbName: 'graceful' });
    const backend = new CrashableStoreBackend(store);

    await backend.write('k', new TextEncoder().encode('PENDING').buffer as ArrayBuffer);
    expect(store.hasPending()).toBe(true);

    // close() 不丢弃 pending（真实 OPFSBackend.close 还会等写队列排空）
    await backend.close();
    expect(store.hasPending()).toBe(true);

    // 提交后才可见 —— 证明"用 close 当崩溃"会掩盖崩溃窗口
    backend.commit();
    expect(decodeBytes(await store.read('k'))).toBe('PENDING');
  });
});