import { createServer } from 'http';
import { appendFile, mkdir, readFile, stat } from 'fs/promises';
import { existsSync, createReadStream } from 'fs';
import { resolve, extname } from 'path';

const PORT = process.env.PORT || 3000;
const HOST = '0.0.0.0';
const PUBLIC_DIR = resolve('./public');
const DATA_DIR = resolve('./data');
const CSV = resolve(DATA_DIR, 'signups.csv');
const emailSet = new Set();

const mime = { '.html':'text/html','.js':'application/javascript','.css':'text/css' };

async function ensureFile() {
  await mkdir(DATA_DIR, { recursive:true });
  if(!existsSync(CSV)) await appendFile(CSV, 'timestamp,email\n');
}

function validEmail(e){return /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(e);}

async function serveFile(path, res){
  try{
    const st=await stat(path);
    res.writeHead(200,{'Content-Type':mime[extname(path)]||'text/plain'});
    createReadStream(path).pipe(res);
  }catch{res.writeHead(404).end('Not found');}
}

createServer(async (req,res)=>{
  if(req.url==='/api/subscribe' && req.method==='POST'){
    let body='';for await(const c of req)body+=c;
    try{
      const {email}=JSON.parse(body);
      if(!validEmail(email)){res.writeHead(400).end('Invalid');return;}
      if(emailSet.has(email)){res.writeHead(200).end('OK');return;}
      const line=`${new Date().toISOString()},${email}\n`;
      await appendFile(CSV,line);emailSet.add(email);
      res.writeHead(200).end('Saved');
    }catch{res.writeHead(500).end('Error');}
    return;
  }
  const path = req.url==='/'?resolve(PUBLIC_DIR,'index.html'):resolve(PUBLIC_DIR,req.url.slice(1));
  serveFile(path,res);
}).listen(PORT,HOST,async()=>{
  await ensureFile();
  console.log(`Running on http://${HOST}:${PORT}`);
});