/**
 * AriaEngine MVCC 事务隔离 + Savepoint 测试
 * 全部 MemoryBackend，零卡死
 */
import { AriaEngine } from '../../src/engine/aria/index';
import { createSchema } from '../../src/table/schema';

import { resetOPFSMock } from '../helpers/storage-harness';

beforeEach(() => { resetOPFSMock(); });

describe('AriaEngine — MVCC 事务 + Savepoint', () => {
  let engine: AriaEngine;

  beforeEach(async () => {
    engine = new AriaEngine({ storageBackend: 'memory' });
    await engine.open('mvcc-test', 1);
    await engine.createTable(createSchema('users', {
      id: { type: 'string', primaryKey: true },
      name: { type: 'string', required: true },
      balance: { type: 'number', default: 0 },
    }));
  });

  afterEach(async () => { await engine.close(); });

  // ---- MVCC 事务 ----
  it('beginTransaction 分配唯一事务ID', () => {
    const id1 = (engine as any).mvcc.beginTransaction();
    const id2 = (engine as any).mvcc.beginTransaction();
    expect(id1).not.toBe(id2);
  });

  it('commit 后清理本事务版本（undo 记录不保留，v0.6.3）', () => {
    const txnId = (engine as any).mvcc.beginTransaction();
    (engine as any).mvcc.writeVersion('users', '1', { name: 'Alice' }, txnId);
    (engine as any).mvcc.commitTransaction(txnId);
    const store = (engine as any).mvcc.versionStore;
    // v0.6.3: 已提交版本随 commit 清理（快照读取已移除，版本链仅作事务内 undo）
    expect(store.has('users.1')).toBe(false);
  });

  it('rollback 移除本事务版本', () => {
    const txnId = (engine as any).mvcc.beginTransaction();
    (engine as any).mvcc.writeVersion('users', '1', { name: 'Alice' }, txnId);
    (engine as any).mvcc.rollbackTransaction(txnId);
    const store = (engine as any).mvcc.versionStore;
    expect(store.has('users.1')).toBe(false);
  });

  it('引擎层事务 commit 后数据可见', async () => {
    await engine.beginTransaction();
    await engine.insert('users', [{ id: '1', name: 'Alice', balance: 100 }]);
    await engine.commitTransaction();
    expect(await engine.count('users')).toBe(1);
  });

  it('引擎层事务 rollback 后数据消失', async () => {
    await engine.insert('users', [{ id: '1', name: 'Alice' }]);
    await engine.beginTransaction();
    await engine.insert('users', [{ id: '2', name: 'Bob' }]);
    await engine.rollbackTransaction();
    expect(await engine.count('users')).toBe(1);
  });

  it('GC 清理过旧版本（未提交版本链保留最新 N 个）', () => {
    for (let i = 0; i < 200; i++) {
      const txnId = (engine as any).mvcc.beginTransaction();
      (engine as any).mvcc.writeVersion('users', '1', { ver: i }, txnId);
      // 不 commit：未提交版本保留在链上（活跃事务 undo）
    }
    (engine as any).mvcc.gc(50);
    expect((engine as any).mvcc.versionStore.get('users.1').length).toBe(50);
  });

  it('多事务并发未提交 + 部分提交：commit 版本清理、未提交保留', () => {
    const mvcc = (engine as any).mvcc;
    const txnA = mvcc.beginTransaction();
    mvcc.writeVersion('users', '1', { name: 'A1' }, txnA);
    const txnB = mvcc.beginTransaction();
    mvcc.writeVersion('users', '1', { name: 'B1' }, txnB);
    mvcc.commitTransaction(txnA);
    // txnA 版本已清理；txnB 未提交版本保留
    const versions = mvcc.versionStore.get('users.1') as { txnId: number }[];
    expect(versions.map((v) => v.txnId)).toEqual([txnB]);
    mvcc.rollbackTransaction(txnB);
    expect(mvcc.versionStore.has('users.1')).toBe(false);
  });

  // ---- Savepoint ----
  it('savepoint 创建成功', async () => {
    await engine.beginTransaction();
    await (engine as any).savepoint('sp1');
    expect((engine as any).savepoints.has('sp1')).toBe(true);
    await engine.rollbackTransaction();
  });

  it('rollbackToSavepoint 恢复快照', async () => {
    await engine.insert('users', [{ id: '1', name: 'Alice' }]);
    await engine.beginTransaction();
    await engine.insert('users', [{ id: '2', name: 'Bob' }]);
    await (engine as any).savepoint('sp1');
    await engine.insert('users', [{ id: '3', name: 'Charlie' }]);
    await (engine as any).rollbackToSavepoint('sp1');
    await engine.commitTransaction();
    expect(await engine.count('users')).toBe(2);
  });

  it('releaseSavepoint 释放后不可回滚', async () => {
    await engine.beginTransaction();
    await (engine as any).savepoint('sp1');
    await (engine as any).releaseSavepoint('sp1');
    expect((engine as any).savepoints.has('sp1')).toBe(false);
    await engine.rollbackTransaction();
  });

  it('重复 savepoint 名称抛出错误', async () => {
    await engine.beginTransaction();
    await (engine as any).savepoint('sp1');
    await expect((engine as any).savepoint('sp1')).rejects.toThrow('already exists');
    await engine.rollbackTransaction();
  });
});