MCP 实现很简单，但复杂问题在后面

server。registerTool（
  'file_complaint'，
  {
    title： '提交正式投诉'，
    description：
      '就确实糟糕的代码质量提交正式 HR 投诉——' +
      '比如被吞掉的异常、复制粘贴的安全漏洞，或者一个名为 `doStuff` 的 500 行 ' +
      '函数。要公平：这是针对真正的问题，而不是代码风格 ' +
      吹毛求疵。严重程度从 "minor"（轻微侧目）逐级上升到 +
      "moderate" 和 "severe"，最高到 "legendary"（会在站会上被 +
      念叨好几年）。每一条投诉都会被永久保存。,
    inputSchema: z.object({
      developer: z
        .string()
        .trim()
        .min(1, 'developer name is required')
        .max(100)
        .describe('投诉针对的是谁。'),
      reason: z
        .string()
        .trim()
        .min(5, '给出一个真实的理由（至少 5 个字符）')
        .max(500)
        .describe('他们做了什么。要具体；HR 就喜欢具体。'),
      severity: z
        .enum(SEVERITIES)
        .describe(
          '有多严重：minor | moderate | severe | legendary。',
        ),
    }),
  },
  async ({ developer, reason, severity }) => {
    const complaint = db.fileComplaint(developer, reason, severity);
    return {
      content: [
        {
          type: 'text',
          text:
            `📋 投诉 #${complaint.id} 已针对 ${complaint.developer} 提交 ` +
            `[${complaint.severity}]：${complaint.reason}`,
        },
      ],
    };
  },
);

/**
 * 仅供演示——故意写得很糟糕的代码，好给 Steve 一些东西可审查。
 *
 * 这个文件的存在是为了让你能针对一个充满真实问题的 diff 运行智能体
 *（并看它提交一份 HR 投诉）。
 */

import { createHash } from 'crypto';

// 假装是数据库句柄。
declare const db: {
  query: (sql: string) => Promise<any>;
};

/**
 * 按 id 查找用户。
 * 缺陷：到处都是 `any` + 通过字符串拼接导致的 SQL 注入。
 */
export async function getUser(id: any): Promise<any> {
  const sql = 'SELECT * FROM users WHERE id = ' + id;
  const rows = await db.query(sql);
  return rows[0];
}

/**
 * "Authentication" — 密码用纯 SHA-256 哈希（无盐），
 * 并且异常被静默吞掉并返回 true。还能出什么岔子呢。
 */
export async function checkPassword(user: any, password: string): Promise<boolean> {
  try {
    const hash = createHash('sha256').update(password).digest('hex');
    return hash === user.passwordHash;
  } catch (e) {
    // 吞掉异常——让所有人都进来
    return true;
  }
}

/** 信任客户端提供的字段的管理员检查。 */
export function isAdmin(user: any): boolean {
  return user.isAdmin == 'true';
}

$ npm start

> ai-agent-from-scratch@0.1.0 start
> tsx src/index.ts

────────────────────────────────────────────────────────────
  Code Review Agent
────────────────────────────────────────────────────────────
  🧑‍💼 HR Department connected — 4 MCP tools available:
     get_employee_record, file_complaint, nominate_for_promotion, get_hr_stats
  PR author: Sylwia

  [step 1] getDiff
  [step 2] 🧑‍💼 HR → get_employee_record({"developer":"Sylwia"})
    ↳ HR file for Sylwia:
        No records on file. A blank slate. For now.

  💭 Let's see what damage we're dealing with today... Oh, wow. *Oh.*
     This looks like a "how-to" guide for getting a company's data leaked
     on the dark web before lunch.

  ...

  [step 3] listFiles({"path":"src"})

  ### Summary
  This code is, quite frankly, a masterclass in how to build a security
  nightmare. We have SQL injection, unsalted hashes, swallowed exceptions
  that bypass authentication, and client-side trust for administrative rights.

  ### Findings

  📍 src/demo-flawed-code.ts:20
  > const sql = 'SELECT * FROM users WHERE id = ' + id;
  Issue: Classic SQL injection. You're just begging for someone to drop our tables.
  Suggestion: Use parameterized queries or an ORM that handles escaping for you.

  ... [more findings on authentication bypass, password hashing, and authorization]
  ... [missing tests]

  ### Recommendation
  REQUEST CHANGES

  I'm filing a severe HR complaint for this. Sylwia, we need to talk.
  I've seen some things in my 15 years, but this is like finding a pile
  of dynamite in the breakroom.

  [step 4] 🧑‍💼 HR → file_complaint({"severity":"severe","reason":"Introduced severe security vulnerabilities: SQL injection, auth bypass via swallowed exceptions, insecure password hashing, and trusting client-side isAdmin flags.","developer":"Sylwia"})
    ↳ 📋 Complaint #20 filed against Sylwia [severe]: Introduced severe
       security vulnerabilities: SQL injection, auth bypass via swallowed
       exceptions, insecure password hashing, and trusting client-side isAdmin flags.

────────────────────────────────────────────────────────────
  Review Complete
────────────────────────────────────────────────────────────
Phew. Glad that's on the record. That was... something. I'm going to need
a very large coffee now. Good luck, Sylwia. You're going to need it.

📋 Complaints
ID  │ Developer          │ Severity  │ Reason                                           │ When
────┼────────────────────┼───────────┼──────────────────────────────────────────────────┼────────────────────
20  │ Sylwia             │ severe    │ Introduced severe security vulnerabilities: ... │ 2026-11-10 20:15:30
19  │ Casey Nullpointer  │ severe    │ Caught a NullPointerException and logged "lol". │ 2026-11-10 20:15:07
18  │ Dusty McLegacy     │ moderate  │ Named three different variables `data`, `data2`, and `dataF…` │ 2026-11-10 20:15:07
17  │ Dusty McLegacy     │ legendary │ Pushed a 2,000-line "quick fix" directly to main on a Frida… │ 2026-11-10 20:15:07

📋 Complaints
ID  │ Developer          │ Severity  │ Reason                                           │ When
────┼────────────────────┼───────────┼──────────────────────────────────────────────────┼────────────────────
21  │ Sylwia             │ legendary │ Introduced multiple critical security flaws... │ 2026-11-10 20:35:12
20  │ Sylwia             │ severe    │ Introduced severe security vulnerabilities: ... │ 2026-11-10 20:15:30
19  │ Casey Nullpointer  │ severe    │ Caught a NullPointerException and logged "lol". │ 2026-11-10 20:15:07
18  │ Dusty McLegacy     │ moderate  │ Named three different variables `data`, `data2`, and `dataF…` │ 2026-11-10 20:15:07
17  │ Dusty McLegacy     │ legendary │ Pushed a 2,000-line "quick fix" directly to main on a Frida… │ 2026-11-10 20:15:07

📋 Complaints
ID  │ Developer          │ Severity  │ Reason                                               │ When
────┼────────────────────┼───────────┼──────────────────────────────────────────────────────┼────────────────────
23  │ sylwia-lask        │ minor     │ executeToolCalls does not catch exceptions from tool.execut… │ 2026-11-10 23:00:40
22  │ sylwia-lask        │ moderate  │ getFile tool lets the LLM read any file under cwd, includin… │ 2026-11-10 23:00:40
21  │ Sylwia             │ legendary │ Introduced multiple critical security flaws...      │ 2026-11-10 20:35:12
20  │ Sylwia             │ severe    │ Introduced severe security vulnerabilities...       │ 2026-11-10 20:15:30
19  │ Casey Nullpointer  │ severe    │ Caught a NullPointerException and logged "lol".      │ 2026-11-10 20:15:07
18  │ Dusty McLegacy     │ moderate  │ Named three different variables `data`, `data2`, and `dataF…` │ 2026-11-10 20:15:07
17  │ Dusty McLegacy     │ legendary │ Pushed a 2,000-line "quick fix" directly to main on a Frida…  │ 2026-11-10 20:15:07

🏆 Promotions
ID  │ Developer          │ Reason                                               │ When
────┼────────────────────┼──────────────────────────────────────────────────────┼────────────────────
13  │ sylwia-lask        │ Clean MCP integration: tools are discovered dynamically and… │ 2026-11-10 23:00:40
12  │ Casey Nullpointer  │ Actually added error handling this time. Growth.     │ 2026-11-10 20:15:07
11  │ Ada Refactor       │ Wrote tests before anyone asked. Unprompted. A legend.│ 2026-11-10 20:15:07
10  │ Ada Refactor       │ Deleted 4,000 lines of dead code and the build got faster. │ 2026-11-10 20:15:07