async function handleRequest(request, env) {
  const { pathname, search } = new URL(request.url);
  // directly proxy the request if path matches official site's
  if (pathname === '/v1/chat/completions')
    return fetch(`https://api.openai.com/v1/chat/completions`, {
      method: request.method,
      headers: request.headers,
      body: request.body,
    });
  
  const [_, token, action, user, ...params] = pathname.split('/');
  if (!token || !action)
    throw 'Invalid request';

  // register or refresh user's token
  if (action === 'register') {
    // validate against master token
    if (token !== env.ACCESS_TOKEN || !user)
      throw 'Access forbidden';
    
    const text = await registerUser(user, env.OPENAI);
    return new Response(text, {
      headers: { 'Content-Type': 'text/plain' }
    });
  } else if (action !== 'chat' || request.method !== 'POST')
    throw 'Invalid action';

  // validate user
  const users = await env.OPENAI.get("users", {type: 'json'}) || {};
  let name;
  for (let key in users)
    if (users[key].uuid === token)
      name = key;
  if (!name)
    throw 'Invalid token';
  
  console.log(`User ${name} acepted.`);
  
  // proxy the request
  const url = new URL(request.url);

  // 1. force set API key and model
  const headers = new Headers(request.headers);
  headers.set('Authorization', `Bearer ${env.API_KEY}`);
  const payload = await request.json();
  payload.model = 'gpt-3.5-turbo';

  // 2. issue the underlying request
  return fetch(`https://api.openai.com/v1/chat/completions`, {
    method: request.method,
    headers: headers,
    body: JSON.stringify(payload),
  });
}

async function registerUser(user, kv) {
  const users = await kv.get("users", {type: 'json'}) || {};
  const uuid = generateUUID();
  users[user] = {uuid};
  await kv.put("users", JSON.stringify(users));
  return uuid;
}

function generateUUID() {
  var d = new Date().getTime();
  if (typeof performance !== 'undefined' && typeof performance.now === 'function'){
    d += performance.now(); // use high-precision timer if available
  }
  var uuid = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
    var r = (d + Math.random()*16)%16 | 0;
    d = Math.floor(d/16);
    return (c=='x' ? r : (r&0x3|0x8)).toString(16);
  });
  return uuid;
}

export default {
  async fetch(request, env) {
    return handleRequest(request, env).catch( err => new Response(err || 'Unknown reason', { status: 403 }))
  }
};