'use strict';

// 迷你路由（零依赖）：
//   const app = createRouter();
//   app.get('/api/job/:id', handler);   // :段 提取参数
//   app.any('/api/reports/status', h);  // 不限方法（保持旧行为）
//   app.fallback(serveStatic);          // 未命中路由时兜底
//   http.createServer((req, res) => app.dispatch(req, res));
// 处理器签名：async ({ req, res, pathname, query, params })，异常由错误边界统一响应。

const { errorBoundary } = require('./middleware.js');
const { sendJson } = require('./util.js');

function toSegments(pattern) {
  return pattern.split('/').filter(Boolean)
    .map((seg) => (seg.startsWith(':') ? { name: seg.slice(1) } : seg));
}

function createRouter() {
  const routes = [];
  let fallbackHandler = null;

  function add(method, pattern, handler) {
    routes.push({ method, segments: toSegments(pattern), handler: errorBoundary(handler) });
  }

  return {
    get: (p, h) => add('GET', p, h),
    post: (p, h) => add('POST', p, h),
    del: (p, h) => add('DELETE', p, h),
    any: (p, h) => add('*', p, h),
    fallback: (fn) => { fallbackHandler = fn; },

    async dispatch(req, res) {
      let pathname;
      let searchParams;
      try {
        const parsedUrl = new URL(req.url, `http://${req.headers.host}`);
        pathname = parsedUrl.pathname;
        searchParams = parsedUrl.searchParams;
      } catch {
        res.writeHead(400);
        return res.end('bad url');
      }
      const query = Object.fromEntries(searchParams);
      const parts = pathname.split('/').filter(Boolean);

      let pathMatched = false;
      for (const route of routes) {
        if (route.segments.length !== parts.length) continue;
        const params = {};
        let ok = true;
        for (let i = 0; i < parts.length; i++) {
          const seg = route.segments[i];
          if (typeof seg === 'string') {
            if (seg !== parts[i]) { ok = false; break; }
          } else {
            params[seg.name] = parts[i];
          }
        }
        if (!ok) continue;
        pathMatched = true;
        if (route.method !== '*' && route.method !== req.method) continue;
        return route.handler({ req, res, pathname, query, params });
      }

      if (pathMatched) return sendJson(res, 405, { error: 'Method Not Allowed' });
      if (fallbackHandler) return fallbackHandler(pathname, res);
      res.writeHead(404);
      res.end('Not found');
    },
  };
}

module.exports = { createRouter };