/**
 * generate-changelog.js — 从 git log 生成 CHANGELOG.md
 *
 * 逻辑：
 *   1. 读取 LAST_BUILD 文件（记录上次构建的 commit hash）
 *   2. 从 LAST_BUILD 到 HEAD 收集 commit messages
 *   3. 按 conventional-commit 分类 (Feat/Fix/Refactor/Chore/Docs/…)
 *   4. 追加到 CHANGELOG.md 末尾并更新 LAST_BUILD
 *
 * 用法: node scripts/generate-changelog.js <version>
 */
const fs = require('fs');
const path = require('path');
const { execSync } = require('child_process');

const rootDir = path.resolve(__dirname, '..');
const version = process.argv[2];
if (!version) {
  console.error('[generate-changelog] 用法: node scripts/generate-changelog.js <version>');
  process.exit(1);
}

const lastBuildFile = path.join(rootDir, '.last_build_commit');
const changelogFile = path.join(rootDir, 'public', 'CHANGELOG.md');

// 获取上次构建 commit hash
let fromHash = '';
try {
  fromHash = fs.readFileSync(lastBuildFile, 'utf-8').trim();
} catch {
  // 首次构建：从第一个 commit 开始
  try {
    fromHash = execSync('git rev-list --max-parents=0 HEAD', { cwd: rootDir, encoding: 'utf-8' }).trim();
  } catch {
    fromHash = '';
  }
}

// 获取当前 HEAD
const headHash = execSync('git rev-parse HEAD', { cwd: rootDir, encoding: 'utf-8' }).trim();

// 获取 commit 日志
let log = '';
try {
  const range = fromHash ? `${fromHash}..HEAD` : 'HEAD';
  log = execSync(
    `git log --no-merges --pretty=format:"%s|||%b|||%an|||%ai" ${range}`,
    { cwd: rootDir, encoding: 'utf-8' }
  ).trim();
} catch {
  log = '';
}

// 解析 commit
const commits = log ? log.split('\n').filter(Boolean).map(line => {
  const [subject, body, author, date] = line.split('|||');
  return { subject: subject || '', body: body || '', author: author || '', date: date || '' };
}) : [];

if (commits.length === 0) {
  console.log('[generate-changelog] 没有新 commit，跳过 changelog 生成');
  // 仍然更新 LAST_BUILD
  fs.writeFileSync(lastBuildFile, headHash, 'utf-8');
  return;
}

const hasMeaningful = commits.some(c => {
  const cat = categorize(c.subject);
  return cat !== '工程化';
});
if (!hasMeaningful) {
  console.log('[generate-changelog] 仅有工程化变更，跳过 changelog 生成');
  fs.writeFileSync(lastBuildFile, headHash, 'utf-8');
  return;
}

// 分类
function categorize(subject) {
  const s = subject.toLowerCase();
  if (s.startsWith('feat') || s.startsWith('feature')) return '新功能';
  if (s.startsWith('fix') || s.startsWith('bug')) return 'Bug 修复';
  if (s.startsWith('refactor')) return '重构';
  if (s.startsWith('docs') || s.startsWith('doc')) return '文档';
  if (s.startsWith('chore') || s.startsWith('build') || s.startsWith('ci')) return '工程化';
  if (s.startsWith('perf') || s.startsWith('optimize')) return '性能优化';
  if (s.startsWith('style')) return '样式';
  if (s.startsWith('test')) return '测试';
  return '其他';
}

const grouped = {};
commits.forEach(c => {
  const cat = categorize(c.subject);
  if (!grouped[cat]) grouped[cat] = [];
  // 格式化 subject：去掉 feat/fix: 前缀
  let desc = c.subject.replace(/^(feat|feature|fix|refactor|docs?|chore|build|ci|perf|style|test)(\([^)]*\))?[:\s]*/i, '');
  if (!desc) desc = c.subject;
  grouped[cat].push(`- ${desc}`);
});

// 构建新版本 changelog 块
const now = new Date().toISOString().slice(0, 10);
let block = `\n## v${version} (${now})\n\n`;
for (const [cat, items] of Object.entries(grouped)) {
  if (cat === '工程化') continue;
  block += `### ${cat}\n${items.join('\n')}\n\n`;
}

// 追加或新建 CHANGELOG.md
let existing = '';
try {
  existing = fs.readFileSync(changelogFile, 'utf-8');
} catch {
  existing = '# 更新日志 (Changelog)\n\n此文件记录所有构建版本的变更。\n';
}
// 新版本插入到标题之后、旧内容之前
const headerEnd = existing.indexOf('\n## ');
if (headerEnd === -1) {
  existing = existing.trimEnd() + block;
} else {
  existing = existing.slice(0, headerEnd) + block + existing.slice(headerEnd);
}
fs.writeFileSync(changelogFile, existing, 'utf-8');

// 更新 LAST_BUILD
fs.writeFileSync(lastBuildFile, headHash, 'utf-8');

console.log(`[generate-changelog] CHANGELOG.md 已更新，新增 ${commits.length} 条记录`);