name: Rules Guard

on:
  pull_request_target:
    types:
      - opened
      - synchronize
      - reopened
      - edited

permissions:
  contents: read
  pull-requests: write

concurrency:
  group: rules-${{ github.event.pull_request.number }}
  cancel-in-progress: false

jobs:
  guard:
    runs-on: ubuntu-latest
    timeout-minutes: 5
    steps:
      # 只查询 PR 元数据，禁止检出或执行贡献分支中的代码。
      - name: Check protected files
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
        with:
          script: |
            const { owner, repo } = context.repo;
            const pr = context.payload.pull_request;
            const params = { owner, repo, pull_number: pr.number };
            const files = await github.paginate(github.rest.pulls.listFiles, {
              ...params,
              per_page: 100,
            });
            // 按 PR 作者识别官方机器人，维护者重开或编辑 PR 时仍使用同一判断
            const isDependabot = pr.user.login === 'dependabot[bot]'
              && pr.user.type === 'Bot'
              && pr.head.repo?.full_name === `${owner}/${repo}`;
            const isDependencyUpdate = file => isDependabot
              && file.status === 'modified'
              && (/^\.github\/workflows\/[^/]+\.ya?ml$/.test(file.filename)
                || /^\.github\/actions\/.+\/(?:action\.ya?ml|Dockerfile)$/.test(file.filename));
            const isProtectedRule = path => typeof path === 'string'
              && (path === 'AGENTS.md' || path.endsWith('/AGENTS.md')
                || path === 'CONTRIBUTING.md'
                || path === '.agents/skills' || path.startsWith('.agents/skills/')
                || path === '.github' || path.startsWith('.github/'));

            // 依赖更新只豁免已有文件的修改，重命名前后的受保护路径仍参与检查
            if (!files.some(file => !isDependencyUpdate(file)
              && (isProtectedRule(file.filename) || isProtectedRule(file.previous_filename)))) {
              core.info('No protected contribution rule changes detected.');
              return;
            }

            // 旧事件不处理后续提交，也不重复处理已关闭的 PR。
            const { data: current } = await github.rest.pulls.get(params);
            if (current.state !== 'open' || current.head.sha !== pr.head.sha) {
              core.info('Pull request state has changed; skipping this event.');
              return;
            }

            // 通知标记保持稳定，以便复用机器人已有评论，避免重复提醒
            const marker = '<!-- agents-md-guard -->';
            const body = [
              marker,
              '我看到这个 PR 涉及受保护的协作规则文件，按仓库约定需要先关闭',
              '',
              '保护范围包括根目录或子目录的 `AGENTS.md`、根目录的 `CONTRIBUTING.md`，以及 `.agents/skills/` 和 `.github/` 中的所有文件，涵盖新增、修改、删除和重命名',
              '',
              '麻烦先撤销这些变更，再重新打开 PR；如果希望调整协作规则，可以先提个 Issue 说明原因和建议，交由维护者处理，感谢理解',
            ].join('\n');

            try {
              const comments = await github.paginate(github.rest.issues.listComments, {
                owner, repo, issue_number: pr.number, per_page: 100,
              });
              const notification = comments.find(comment => comment.user?.login === 'github-actions[bot]'
                && comment.body?.includes(marker));
              if (!notification) {
                await github.rest.issues.createComment({ owner, repo, issue_number: pr.number, body });
              } else if (notification.body !== body) {
                await github.rest.issues.updateComment({ owner, repo, comment_id: notification.id, body });
              }
            } catch (error) {
              core.warning(`Unable to post policy explanation: ${error.message}`);
            }

            await github.rest.pulls.update({ ...params, state: 'closed' });
            core.setFailed('Pull requests must not change protected contribution rules (AGENTS.md, CONTRIBUTING.md, .agents/skills/, .github/).');