/**
 * 客户端静态资源托管（任务 A1.5）。
 *
 * 构建后的客户端（client/app/dist）由平台服务托管，这样一个端口就能跑起完整平台——
 * 桌面端与浏览器都指向同一个服务地址。未构建时返回 false，由调用方按 404 处理。
 */
import { existsSync } from 'node:fs';
import { readFile } from 'node:fs/promises';
import type { ServerResponse } from 'node:http';
import { extname, join, normalize, resolve, sep } from 'node:path';
import { fileURLToPath } from 'node:url';

const MIME_TYPES: Record<string, string> = {
  '.html': 'text/html; charset=utf-8',
  '.js': 'text/javascript; charset=utf-8',
  '.css': 'text/css; charset=utf-8',
  '.json': 'application/json; charset=utf-8',
  '.svg': 'image/svg+xml',
  '.png': 'image/png',
  '.jpg': 'image/jpeg',
  '.woff2': 'font/woff2',
};

/** 默认目录：仓库内 client/app/dist；可用 APS_CLIENT_DIST 覆盖 */
export function clientDistDir(): string {
  const override = process.env.APS_CLIENT_DIST;
  if (override && override.trim() !== '') return resolve(override);
  // server/dist/entry/static.js → 仓库根
  return fileURLToPath(new URL('../../../client/app/dist', import.meta.url));
}

export function createStaticHandler(root = clientDistDir()): (urlPath: string, res: ServerResponse) => Promise<boolean> {
  const rootDir = resolve(root);
  const indexFile = join(rootDir, 'index.html');

  return async function serveStatic(urlPath: string, res: ServerResponse): Promise<boolean> {
    if (!existsSync(indexFile)) return false;

    const relativePath = normalize(decodeURIComponent(urlPath)).replace(/^[/\\]+/, '');
    const candidate = resolve(rootDir, relativePath);
    const insideRoot = candidate === rootDir || candidate.startsWith(rootDir + sep);
    if (!insideRoot) return false; // 目录穿越

    const file = relativePath === '' || !existsSync(candidate) || !extname(candidate) ? indexFile : candidate;
    const body = await readFile(file);
    res.writeHead(200, {
      'content-type': MIME_TYPES[extname(file)] ?? 'application/octet-stream',
      'cache-control': file === indexFile ? 'no-store' : 'public, max-age=3600',
    });
    res.end(body);
    return true;
  };
}