/**
 * Минимальный HTTP-сервер без Express: node:http / node:http2
 */
import fs from 'node:fs';
import path from 'node:path';
import http from 'node:http';
import http2 from 'node:http2';
import crypto from 'node:crypto';
import { fileURLToPath } from 'node:url';

const MIME = {
  '.html': 'text/html; charset=utf-8',
  '.css': 'text/css; charset=utf-8',
  '.js': 'application/javascript; charset=utf-8',
  '.json': 'application/json; charset=utf-8',
  '.ico': 'image/x-icon',
  '.svg': 'image/svg+xml',
  '.png': 'image/png',
};

export function loadEnv(envPath) {
  if (!fs.existsSync(envPath)) return;
  for (const line of fs.readFileSync(envPath, 'utf8').split('\n')) {
    const t = line.trim();
    if (!t || t.startsWith('#')) continue;
    const i = t.indexOf('=');
    if (i < 0) continue;
    const key = t.slice(0, i).trim();
    let val = t.slice(i + 1).trim();
    if ((val.startsWith('"') && val.endsWith('"')) || (val.startsWith("'") && val.endsWith("'"))) {
      val = val.slice(1, -1);
    }
    if (!(key in process.env)) process.env[key] = val;
  }
}

export function sendJson(res, status, data) {
  const body = JSON.stringify(data);
  res.writeHead(status, {
    'Content-Type': 'application/json; charset=utf-8',
    'Content-Length': Buffer.byteLength(body),
  });
  res.end(body);
}

export function readJsonBody(req) {
  return new Promise((resolve, reject) => {
    const chunks = [];
    req.on('data', (c) => chunks.push(c));
    req.on('end', () => {
      if (!chunks.length) return resolve({});
      try {
        resolve(JSON.parse(Buffer.concat(chunks).toString('utf8')));
      } catch {
        reject(new Error('Invalid JSON'));
      }
    });
    req.on('error', reject);
  });
}

export function parseCookies(req) {
  const raw = req.headers.cookie || '';
  const out = {};
  for (const part of raw.split(';')) {
    const [k, ...v] = part.trim().split('=');
    if (k) out[k] = decodeURIComponent(v.join('='));
  }
  return out;
}

export function setCookie(res, name, value, opts = {}) {
  const parts = [`${name}=${encodeURIComponent(value)}`, 'Path=/', 'HttpOnly', 'SameSite=Lax'];
  if (opts.maxAge) parts.push(`Max-Age=${opts.maxAge}`);
  if (opts.clear) parts.push('Max-Age=0');
  const prev = res.getHeader('Set-Cookie');
  const next = Array.isArray(prev) ? [...prev, parts.join('; ')] : prev ? [prev, parts.join('; ')] : [parts.join('; ')];
  res.setHeader('Set-Cookie', next);
}

export function signSession(data, secret) {
  const payload = Buffer.from(JSON.stringify(data)).toString('base64url');
  const sig = crypto.createHmac('sha256', secret).update(payload).digest('base64url');
  return `${payload}.${sig}`;
}

export function verifySession(token, secret) {
  if (!token) return null;
  const dot = token.lastIndexOf('.');
  if (dot < 0) return null;
  const payload = token.slice(0, dot);
  const sig = token.slice(dot + 1);
  const expected = crypto.createHmac('sha256', secret).update(payload).digest('base64url');
  if (sig !== expected) return null;
  try {
    return JSON.parse(Buffer.from(payload, 'base64url').toString('utf8'));
  } catch {
    return null;
  }
}

export function clientIp(req) {
  return (req.socket?.remoteAddress || '').replace('::ffff:', '');
}

export function matchRoute(method, pathname, routes) {
  for (const r of routes) {
    if (r.method !== method) continue;
    const pattern = r.path.replace(/:([^/]+)/g, '([^/]+)');
    const re = new RegExp(`^${pattern}$`);
    const m = pathname.match(re);
    if (!m) continue;
    const keys = [...r.path.matchAll(/:([^/]+)/g)].map((x) => x[1]);
    const params = {};
    keys.forEach((k, i) => { params[k] = decodeURIComponent(m[i + 1]); });
    return { handler: r.handler, params };
  }
  return null;
}

export async function serveStatic(publicDir, pathname) {
  const base = path.resolve(publicDir);
  const rel = pathname === '/' ? 'index.html' : pathname.replace(/^\//, '');
  const filePath = path.resolve(base, rel);
  if (!filePath.startsWith(base + path.sep) && filePath !== base) return null;
  try {
    const stat = fs.statSync(filePath);
    if (!stat.isFile()) return null;
    const ext = path.extname(filePath);
    return {
      body: fs.readFileSync(filePath),
      type: MIME[ext] || 'application/octet-stream',
    };
  } catch {
    return null;
  }
}

/** Rate limit: max запросов за windowMs на IP */
export function createRateLimiter({ windowMs, max }) {
  const hits = new Map();
  return (ip) => {
    const now = Date.now();
    let entry = hits.get(ip);
    if (!entry || now - entry.start > windowMs) {
      entry = { start: now, count: 0 };
      hits.set(ip, entry);
    }
    entry.count += 1;
    return entry.count <= max;
  };
}

/**
 * @param {function} onRequest async (req, res, ctx) => void
 * @param {{ http2?: boolean, tls?: { key, cert }, host, port }} opts
 */
export function listen(onRequest, opts) {
  const handler = async (req, res) => {
    try {
      await onRequest(req, res);
    } catch (e) {
      if (!res.headersSent) sendJson(res, 500, { error: e.message || 'Internal error' });
    }
  };

  let server;
  if (opts.tls?.key && opts.tls?.cert) {
    server = http2.createSecureServer(
      { key: fs.readFileSync(opts.tls.key), cert: fs.readFileSync(opts.tls.cert) },
      handler
    );
  } else if (opts.http2) {
    server = http2.createServer(handler);
  } else {
    server = http.createServer(handler);
  }

  server.listen(opts.port, opts.host, () => {
    const proto = opts.tls ? 'https' : 'http';
    const h2 = opts.http2 || opts.tls ? ' HTTP/2' : '';
    console.log(`Listening → ${proto}://${opts.host}:${opts.port}${h2}`);
  });
  return server;
}

export function dirFromMeta(metaUrl) {
  return path.dirname(fileURLToPath(metaUrl));
}