import type { IncomingMessage, ServerResponse } from 'node:http';

export const MAX_BODY_SIZE = 1024 * 1024; // 1 MB

export function sendJSON(res: ServerResponse, status: number, data: unknown): void {
  res.writeHead(status, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify(data));
}

export function sendText(res: ServerResponse, status: number, text: string, contentType = 'text/plain'): void {
  res.writeHead(status, { 'Content-Type': contentType });
  res.end(text);
}

export function parseBody(req: IncomingMessage): Promise<string> {
  return new Promise((resolveP, reject) => {
    const chunks: Buffer[] = [];
    let size = 0;
    req.on('data', (c: Buffer) => {
      size += c.length;
      if (size > MAX_BODY_SIZE) {
        req.destroy();
        reject(new Error('Request body too large'));
        return;
      }
      chunks.push(c);
    });
    req.on('end', () => resolveP(Buffer.concat(chunks).toString()));
    req.on('error', reject);
  });
}

export async function parseJSONBody<T = unknown>(req: IncomingMessage): Promise<T> {
  const body = await parseBody(req);
  return JSON.parse(body) as T;
}

export function parseCookies(req: IncomingMessage): Record<string, string> {
  const cookies: Record<string, string> = {};
  const header = req.headers.cookie || '';
  for (const pair of header.split(';')) {
    const eq = pair.indexOf('=');
    if (eq === -1) continue;
    cookies[pair.slice(0, eq).trim()] = pair.slice(eq + 1).trim();
  }
  return cookies;
}

export function clientIp(req: IncomingMessage): string {
  const xff = (req.headers['x-forwarded-for'] as string | undefined)?.split(',')[0]?.trim();
  return xff || req.socket.remoteAddress || 'unknown';
}