/**
 * generate-changelog.js — 从 git log 生成 changelog，按中版本分文件存储
 *
 * 文件结构：
 *   public/CHANGELOG.md           — 索引页，显示最新版本内容 + 链接到所有版本文件
 *   public/CHANGELOG-v{MAJOR}.{MINOR}.md — 每个中版本一个文件
 *
 * 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 PUBLIC_DIR = path.join(rootDir, 'public');
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(PUBLIC_DIR, 'CHANGELOG.md');

const versionParts = version.split('.');
const minorVersion = `${versionParts[0]}.${versionParts[1]}`;
const versionFileName = `CHANGELOG-v${minorVersion}.md`;
const versionFilePath = path.join(PUBLIC_DIR, versionFileName);

// ==================== 1. 获取 commit 日志 ====================

let fromHash = '';
try {
  fromHash = fs.readFileSync(lastBuildFile, 'utf-8').trim();
} catch {
  try {
    fromHash = execSync('git rev-list --max-parents=0 HEAD', { cwd: rootDir, encoding: 'utf-8' }).trim();
  } catch {
    fromHash = '';
  }
}

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

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 = '';
}

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');
  fs.writeFileSync(lastBuildFile, headHash, 'utf-8');
  return;
}

// ==================== 2. 分类 commit ====================

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 hasMeaningful = commits.some(c => categorize(c.subject) !== '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;
}

const grouped = {};
commits.forEach(c => {
  const cat = categorize(c.subject);
  if (!grouped[cat]) grouped[cat] = [];
  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}`);
});

// ==================== 3. 构建版本内容块 ====================

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`;
}

// ==================== 4. 写入版本文件 ====================

let versionContent = '';
try {
  versionContent = fs.readFileSync(versionFilePath, 'utf-8');
} catch {
  versionContent = `# v${minorVersion} 版本历史\n\n[« 返回最新版本](CHANGELOG.md)\n\n---\n`;
}

const versionHeaderEnd = versionContent.indexOf('\n## ');
if (versionHeaderEnd === -1) {
  versionContent = versionContent.trimEnd() + block;
} else {
  versionContent = versionContent.slice(0, versionHeaderEnd) + block + versionContent.slice(versionHeaderEnd);
}
fs.writeFileSync(versionFilePath, versionContent, 'utf-8');

// ==================== 5. 迁移旧版 CHANGELOG.md 内容（首次运行） ====================

// 检查是否已有版本文件（除当前文件外），若没有则从旧版 CHANGELOG.md 迁移
const allFiles = fs.readdirSync(PUBLIC_DIR);
const existingVersionFiles = allFiles.filter(f => /^CHANGELOG-v\d+\.\d+\.md$/.test(f) && f !== versionFileName);

if (existingVersionFiles.length === 0) {
  try {
    const legacyContent = fs.readFileSync(changelogFile, 'utf-8');
    // 判断是否是旧版格式（包含 ## v 条目但没有版本导航链接）
    const hasLegacyEntries = /^## v\d+\.\d+\.\d+/m.test(legacyContent);
    const hasVersionNav = legacyContent.includes('版本历史](');
    if (hasLegacyEntries && !hasVersionNav) {
      // 提取所有版本条目，按中版本分组
      const versionRegex = /(## v(\d+\.\d+)\.\d+ .*?)(?=\n## v\d+\.\d+\.\d+ |\n*$)/gs;
      const entries = {};
      let match;
      while ((match = versionRegex.exec(legacyContent)) !== null) {
        const entry = match[1].trim();
        const ver = match[2];
        if (!entries[ver]) entries[ver] = [];
        entries[ver].push(entry);
      }

      for (const [ver, entryList] of Object.entries(entries)) {
        if (ver === minorVersion) continue; // 当前版本已写入
        const vf = path.join(PUBLIC_DIR, `CHANGELOG-v${ver}.md`);
        let vc = '';
        try {
          vc = fs.readFileSync(vf, 'utf-8');
        } catch {
          vc = `# v${ver} 版本历史\n\n[« 返回最新版本](CHANGELOG.md)\n\n---\n`;
        }
        const vhEnd = vc.indexOf('\n## ');
        const migratedBlock = '\n' + entryList.join('\n') + '\n';
        if (vhEnd === -1) {
          vc = vc.trimEnd() + migratedBlock;
        } else {
          vc = vc.slice(0, vhEnd) + migratedBlock + vc.slice(vhEnd);
        }
        fs.writeFileSync(vf, vc, 'utf-8');
      }
      console.log(`[generate-changelog] 已迁移 ${Object.keys(entries).length} 个中版本的历史记录`);
    }
  } catch {
    // 没有旧版 CHANGELOG.md，忽略
  }
}

// ==================== 6. 重建主 CHANGELOG.md ====================

const allVersionFiles = fs.readdirSync(PUBLIC_DIR)
  .filter(f => /^CHANGELOG-v(\d+)\.(\d+)\.md$/.test(f))
  .sort((a, b) => {
    // 降序排列：1.1 > 1.0
    const ma = a.match(/^CHANGELOG-v(\d+)\.(\d+)\.md$/);
    const mb = b.match(/^CHANGELOG-v(\d+)\.(\d+)\.md$/);
    if (!ma || !mb) return 0;
    const va = parseInt(ma[1]) * 1000 + parseInt(ma[2]);
    const vb = parseInt(mb[1]) * 1000 + parseInt(mb[2]);
    return vb - va;
  });

const links = allVersionFiles.map(f => {
  const v = f.replace('CHANGELOG-v', '').replace('.md', '');
  return `- [v${v} 版本历史](${f})`;
}).join('\n');

// 读取最新版本文件内容作为默认显示
let latestContent = '';
if (allVersionFiles.length > 0) {
  const latestFile = allVersionFiles[0];
  latestContent = fs.readFileSync(path.join(PUBLIC_DIR, latestFile), 'utf-8');
  // 去掉文件头（标题 + 返回链接 + 分隔线）
  latestContent = latestContent.replace(/^# .+?\n\n\[.+?\]\(.+?\)\n\n---\n\n/s, '');
}

const mainContent = `# 更新日志

> 当前版本: v${version}

## 历史版本

${links}

---

${latestContent}
`;

fs.writeFileSync(changelogFile, mainContent, 'utf-8');

// ==================== 7. 更新 LAST_BUILD ====================

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

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