Codex批量修改Markdown：解析标题、预演清单与副本验证

npm init -y
npm install --save-exact --ignore-scripts [email protected] [email protected]

---
title: "旧标题"
updated: "2026-10-01"
---
## 旧标题

正文里提到旧标题，不应该被替换。

```markdown
## 旧标题
```

[旧标题](https://example.com)

import fs from 'node:fs';
import path from 'node:path';
import crypto from 'node:crypto';
import MarkdownIt from 'markdown-it';
import matter from 'gray-matter';

const mode = process.argv[2] || 'plan';
if (!['plan', 'apply'].includes(mode)) throw new Error('用法: node rename-heading.mjs plan|apply');
const inputDir = path.resolve('input');
const outputDir = path.resolve('converted');
const planFile = path.resolve('markdown-plan.json');
const md = new MarkdownIt();
const hash = value => crypto.createHash('sha256').update(value).digest('hex');
const names = fs.readdirSync(inputDir).filter(n => n.endsWith('.md')).sort();
const rows = [];
for (const name of names) {
  const file = path.join(inputDir, name);
  if (!fs.lstatSync(file).isFile()) throw new Error('仅处理普通文件: ' + name);
  const buffer = fs.readFileSync(file);
  const raw = buffer.toString('utf8');
  if (!Buffer.from(raw).equals(buffer)) throw new Error('不是有效 UTF-8: ' + name);
  const parsed = matter(raw);
  const body = parsed.content;
  if (!raw.endsWith(body)) throw new Error('无法保留原始头部: ' + name);
  const prefix = raw.slice(0, raw.length - body.length);
  const lines = body.match(/[^\n]*\n|[^\n]+$/g) || [];
  const tokens = md.parse(body, {});
  const changes = [];
  for (let i = 0; i < tokens.length; i++) {
    const t = tokens[i];
    if (t.type !== 'heading_open' || t.tag !== 'h2' || t.level !== 0) continue;
    const inline = tokens[i + 1];
    if (inline.content !== '旧标题') continue;
    const [start, end] = t.map;
    const line = lines[start];
    if (end !== start + 1 || !/^## 旧标题(?:\r?\n)?$/.test(line) ||
        inline.children.length !== 1 || inline.children[0].type !== 'text') {
      throw new Error('标题格式需人工处理: ' + name + ':' + (start + 1));
    }
    lines[start] = line.replace('旧标题', '新标题');
    changes.push({ bodyLine: start + 1, before: '## 旧标题', after: '## 新标题' });
  }
  const after = prefix + lines.join('');
  if (JSON.stringify(matter(after).data) !== JSON.stringify(parsed.data)) {
    throw new Error('元数据变化: ' + name);
  }
  rows.push({ name, sourceHash: hash(buffer), changes, after });
}
const manifest = {
  inputDir, rule: 'top-level plain ATX h2: 旧标题 -> 新标题',
  files: rows.map(({ name, sourceHash, changes }) => ({ name, sourceHash, changes }))
};
if (mode === 'plan') {
  fs.writeFileSync(planFile, JSON.stringify(manifest, null, 2) + '\n');
  console.log(JSON.stringify(manifest, null, 2));
} else {
  const saved = JSON.parse(fs.readFileSync(planFile, 'utf8'));
  if (JSON.stringify(saved) !== JSON.stringify(manifest)) {
    throw new Error('输入或规则已变化，请重新预演并检查');
  }
  // Existing output is deliberately refused; the input is never overwritten.
  fs.mkdirSync(outputDir);
  for (const row of rows) fs.writeFileSync(path.join(outputDir, row.name), row.after, { flag: 'wx' });
  console.log('副本写入 converted；原 input 未改动');
}

node rename-heading.mjs plan
Get-Content -LiteralPath markdown-plan.json
node rename-heading.mjs apply
git diff --no-index -- input converted