import { readFile } from 'node:fs/promises';
import { fileURLToPath } from 'node:url';
import { dirname, extname, join, resolve, sep } from 'node:path';
import type { FastifyInstance, FastifyReply } from 'fastify';

/**
 * Web 看板静态文件服务（零依赖，手写）。
 * web/ 不参与 tsc 构建，直接相对仓库根定位：
 * dev 时本文件在 src/api/，build 后在 dist/api/，两者到仓库根都是 ../..（与 store/db.ts 同思路）。
 */
const HERE = dirname(fileURLToPath(import.meta.url));
const WEB_ROOT = resolve(HERE, '..', '..', 'web');

const MIME: Record<string, string> = {
  '.html': 'text/html; charset=utf-8',
  '.js': 'text/javascript; charset=utf-8',
  '.mjs': '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',
  '.gif': 'image/gif',
  '.ico': 'image/x-icon',
  '.webp': 'image/webp',
  '.woff': 'font/woff',
  '.woff2': 'font/woff2',
  '.map': 'application/json',
  '.txt': 'text/plain; charset=utf-8',
};

async function serveFile(reply: FastifyReply, rawPath: string): Promise<FastifyReply> {
  let rel: string;
  try {
    rel = decodeURIComponent(rawPath);
  } catch {
    return reply.code(400).type('text/plain; charset=utf-8').send('Bad Request');
  }
  if (rel.includes('\0')) {
    return reply.code(400).type('text/plain; charset=utf-8').send('Bad Request');
  }

  // 路径穿越防护：解析后必须仍落在 WEB_ROOT 之内
  const abs = resolve(WEB_ROOT, '.' + sep + rel);
  if (abs !== WEB_ROOT && !abs.startsWith(WEB_ROOT + sep)) {
    return reply.code(403).type('text/plain; charset=utf-8').send('Forbidden');
  }

  const file = abs === WEB_ROOT ? join(WEB_ROOT, 'index.html') : abs;
  try {
    const buf = await readFile(file);
    const type = MIME[extname(file).toLowerCase()] ?? 'application/octet-stream';
    // 本地开发工具：禁启发式缓存，每次重新验证（否则浏览器会吃旧 CSS/JS）
    return reply.header('cache-control', 'no-cache').type(type).send(buf);
  } catch {
    return reply.code(404).type('text/plain; charset=utf-8').send('Not Found');
  }
}

/**
 * 在 Fastify 上注册看板静态路由。
 * `/` → web/index.html；`/*` → web/ 下对应文件（/api/**、/ws 等更具体路由优先匹配，不受影响）。
 */
export function registerStatic(app: FastifyInstance): void {
  app.get('/', (_req, reply) => serveFile(reply, 'index.html'));
  app.get('/*', (req, reply) => {
    const params = req.params as { '*': string };
    return serveFile(reply, params['*'] ?? '');
  });
}