// .github/scripts/ai-review.js
import { App } from '@octokit/app';
import Anthropic from '@anthropic-ai/sdk';

const REVIEW_RULES = `You are a senior software engineer doing a code review.

Review for:
1. Security vulnerabilities (injection, auth issues, exposed secrets)
2. Logic errors and off-by-one bugs
3. Missing error handling (unhandled promises, missing null checks)
4. Performance issues (N+1 queries, unnecessary re-computation)

Do NOT comment on: code style, formatting, naming, or missing tests.

Respond with JSON:
{
  "comments": [
    {
      "path": "src/api/users.ts",
      "line": 42,
      "severity": "error" | "warning",
      "body": "Explanation and how to fix"
    }
  ],
  "summary": "Brief assessment",
  "decision": "APPROVE" | "REQUEST_CHANGES" | "COMMENT"
}`;

async function main() {
  const app = new App({
    appId: process.env.APP_ID,
    privateKey: process.env.APP_PRIVATE_KEY,
  });

  const octokit = await app.getInstallationOctokit(await getInstallationId(app));
  const anthropic = new Anthropic({ apiKey: process.env.ANTHROPIC_API_KEY });

  const { data: diff } = await octokit.rest.pulls.get({
    owner: process.env.REPO_OWNER,
    repo: process.env.REPO_NAME,
    pull_number: parseInt(process.env.PR_NUMBER),
    mediaType: { format: 'diff' }
  });

  const files = parseDiff(diff);
  if (files.length > 50) { console.log('Skipping: too many files'); return; }

  const reviewableFiles = files.filter(f =>
    !f.path.match(/\.(lock|snap|min\.(js|css)|pb\.go)/)
  );

  const allComments = [];
  let overallDecision = 'APPROVE';
  const batchSize = 10;

  for (let i = 0; i < reviewableFiles.length; i += batchSize) {
    const batch = reviewableFiles.slice(i, i + batchSize);
    const diffText = batch.map(f => `--- ${f.path}\n${f.diff}`).join('\n\n');

    const response = await anthropic.messages.create({
      model: 'claude-haiku-4-5',
      max_tokens: 2048,
      system: REVIEW_RULES,
      messages: [{ role: 'user', content: `Review this PR diff:\n\n${diffText}` }]
    });

    const result = JSON.parse(extractJson(response.content[0].text));
    allComments.push(...result.comments);
    if (result.decision === 'REQUEST_CHANGES') overallDecision = 'REQUEST_CHANGES';
  }

  await octokit.rest.pulls.createReview({
    owner: process.env.REPO_OWNER,
    repo: process.env.REPO_NAME,
    pull_number: parseInt(process.env.PR_NUMBER),
    commit_id: process.env.HEAD_SHA,
    event: overallDecision,
    body: `## AI Code Review\n\nFound ${allComments.length} issue(s).\n\n*Powered by Claude*`,
    comments: allComments.map(c => ({
      path: c.path, line: c.line,
      body: `**${c.severity.toUpperCase()}**: ${c.body}`
    }))
  });
}

function extractJson(text) {
  const match = text.match(/\{[\s\S]*\}/);
  if (!match) throw new Error('No JSON in response');
  return match[0];
}

async function getInstallationId(app) {
  for await (const { installation } of app.eachInstallation.iterator()) {
    return installation.id;
  }
  throw new Error('No installation found');
}

function parseDiff(diffText) {
  const files = [];
  let currentFile = null;
  let currentLine = 0;

  for (const line of diffText.split('\n')) {
    if (line.startsWith('+++ b/')) {
      if (currentFile) files.push(currentFile);
      currentFile = { path: line.slice(6), diff: '', changedLines: [] };
      currentLine = 0;
    } else if (line.startsWith('@@ ')) {
      const match = line.match(/@@ -\d+(?:,\d+)? \+(\d+)/);
      if (match) currentLine = parseInt(match[1]) - 1;
    } else if (currentFile) {
      if (line.startsWith('+')) { currentLine++; currentFile.changedLines.push(currentLine); }
      else if (!line.startsWith('-')) currentLine++;
      currentFile.diff += line + '\n';
    }
  }

  if (currentFile) files.push(currentFile);
  return files;
}

main().catch(console.error);

const CUSTOM_RULES = `
Additional rules for this codebase:
- All database queries must use parameterized statements (no string interpolation with user input)
- API endpoints must validate request body with Zod schemas before processing
- React components must not call hooks conditionally
`;