AI 코드 리뷰: GitHub PR 자동 리뷰

// 1. GitHub App 생성
// https://github.com/settings/apps/new
// Permissions: pull_requests (read+write), contents (read)
// Events: pull_request, pull_request_review

// 2. webhook URL 등록
// https://yourservice.com/webhooks/github

// 3. App 설치 (각 repo에)

// app/api/webhooks/github/route.ts
import { Webhooks } from '@octokit/webhooks';

const webhooks = new Webhooks({ secret: process.env.GITHUB_WEBHOOK_SECRET! });

webhooks.on('pull_request.opened', async ({ payload }) => {
  await reviewPR(payload);
});

webhooks.on('pull_request.synchronize', async ({ payload }) => {
  await reviewPR(payload);
});


export async function POST(req: Request) {
  const body = await req.text();
  const signature = req.headers.get('x-hub-signature-256')!;

  await webhooks.verifyAndReceive({
    id: req.headers.get('x-github-delivery')!,
    name: req.headers.get('x-github-event')! as any,
    payload: body,
    signature,
  });

  return new Response('OK');
}

import { Octokit } from '@octokit/rest';

async function reviewPR(payload: any) {
  const { pull_request: pr, repository: repo, installation } = payload;

  const octokit = await getInstallationOctokit(installation.id);

  // diff 가져오기
  const { data: diff } = await octokit.pulls.get({
    owner: repo.owner.login,
    repo: repo.name,
    pull_number: pr.number,
    mediaType: { format: 'diff' },
  });


  // 변경된 파일들
  const { data: files } = await octokit.pulls.listFiles({
    owner: repo.owner.login,
    repo: repo.name,
    pull_number: pr.number,
  });

  return analyzeAndComment(octokit, repo, pr, files, diff as unknown as string);
}

async function analyzeFile(file: any, octokit: any, owner: string, repo: string, prNumber: number) {
  const result = await generateObject({
    model: anthropic('claude-sonnet-4-6'),
    schema: z.object({
      summary: z.string(),
      comments: z.array(z.object({
        line: z.number(),
        severity: z.enum(['nit', 'suggestion', 'issue', 'critical']),
        message: z.string(),
      })),
      overallAssessment: z.enum(['approve', 'request_changes', 'comment']),
    }),
    system: `You are a senior engineer doing code review.

Focus on:
- Bugs and edge cases
- Security issues
- Performance problems
- Type safety
- Error handling
- Test coverage

Don't comment on:
- Pure formatting (if linter exists)
- Personal style preferences
- Things already mentioned by other tools`,
    prompt: `Review this file:

File: ${file.filename}
Language: ${file.filename.split('.').pop()}

Diff:
${file.patch}

Provide line-specific comments. Use line numbers from the new file.`,
  });

  // PR에 review 코멘트 작성
  for (const comment of result.object.comments) {
    await octokit.pulls.createReviewComment({
      owner, repo, pull_number: prNumber,
      body: `**${comment.severity.toUpperCase()}**: ${comment.message}`,
      commit_id: pr.head.sha,
      path: file.filename,
      line: comment.line,
      side: 'RIGHT',
    });
  }

  return result.object;
}

async function postSummary(octokit: any, owner: string, repo: string, prNumber: number, fileReviews: any[]) {
  const result = await generateText({
    model: anthropic('claude-sonnet-4-6'),
    prompt: `Synthesize these file reviews into a PR-level summary:

${fileReviews.map(r => `## ${r.file}\n${r.summary}`).join('\n\n')}

Provide:
1. Top 3 concerns
2. Estimated review priority (low/medium/high)
3. Test recommendations
4. Overall: approve / changes requested`,
  });

  await octokit.issues.createComment({
    owner, repo, issue_number: prNumber,
    body: `## 🤖 AI Review\n\n${result.text}`,
  });
}

PR당 비용:
- 평균 500 lines 변경
- ~10K input tokens + 5K output tokens
- Claude Sonnet: $0.10 per PR


비교:
- 사람 시니어 리뷰: 30분 × $100/시간 = $50

→ AI 리뷰 = 1/500 비용
→ 보조 도구 (사람 검토 전 1차)

[CodeRabbit] (유료 SaaS)
- 즉시 사용
- 무료 plan 있음

[Aider] (오픈소스)
- 자체 구현
- 자유도 높음

[자체 — 본 챕터 코드]
- 완전 커스텀
- 도메인 특화 룰