const http = require('http')
const url = require('url')
const fs = require('fs')
const ws = require('ws')
const redis = require('redis')
const mime = require('mime')
const XMLHttpRequest = require("xmlhttprequest").XMLHttpRequest
const host = 'http://127.0.0.1:8080/'

//redis client
const redis_cli = redis.createClient()
redis_cli.on("error", function (error) {
  console.error(error)
})

const outpath = ['sym', '', 'manifest.json']

//HTTP server
http.createServer(function (req, res) {
  const q = url.parse(req.url, true);
  let filename = "./public" + q.pathname;
  if (filename === "./public/") filename = "./public/index.html";
  let file_type = mime.getType(filename)
  //q.pathname.split("/", 2)[1] === "sym" || )
  if (function valid_path(){//
    for (let i = 0; i < outpath.length; i++) if (q.pathname.split("/", 2)[1] === outpath[i]) return true
    return false
  }() === true){
    fs.readFile(filename, function(err, data) {
      if (err) {
        res.writeHead(404, {'Content-Type': file_type});
        return res.end("404 Not Found");
      }
      res.writeHead(200, {'Content-Type': file_type});
      res.write(data);
      return res.end();
    })
  }else{
    redis_cli.hget("surl;"+q.pathname.split("/", 2)[1], "url", function(err, obj) {
      if(err) console.log(err);
      if(obj){
        res.writeHead(302, {'Location': obj});
        return res.end();
      }else{
        res.writeHead(404, {'Content-Type': file_type});
        return res.end("404 this short-url does not exist :/");
      }
    });
  }
}).listen(8080);

//WS server
const wss = new ws.Server({
  port: 8081,
  perMessageDeflate: {
    zlibDeflateOptions: {
      // See zlib defaults.
      chunkSize: 1024,
      memLevel: 7,
      level: 3
    },
    zlibInflateOptions: {
      chunkSize: 10 * 1024
    },
    // Other options settable:
    clientNoContextTakeover: true, // Defaults to negotiated value.
    serverNoContextTakeover: true, // Defaults to negotiated value.
    serverMaxWindowBits: 10, // Defaults to negotiated value.
    // Below options specified as default values.
    concurrencyLimit: 10, // Limits zlib concurrency for perf.
    threshold: 1024 // Size (in bytes) below which messages
    // should not be compressed.
  }
});

//WS handler
wss.on('connection', ws => {
  ws.on('message', message => {
    console.log(`Received message => ${message}`)
    let msg = `${message}`.split(";", 2)
    if (msg[0] === 'long_url') {
      if (msg[1] === '') ws.send('error;url is empty')
      else if (msg[1].length > 2000) ws.send('error;your url is too long')
      else{
        let xhr = new XMLHttpRequest();
        xhr.onreadystatechange = function() {
          if (xhr.readyState === 4) {
            switch(xhr.status) {
              case 200:
                let ran_key = get_key(4)
                //write to redis
                redis_cli.hmset("surl;"+ran_key, "url", msg[1], "time", Date.now())
                ws.send('surl;'+host+ran_key)
                console.log(ran_key+' --> '+msg[1])
                break;
              case 404: ws.send('error;site does not exist (404)');break;
              case 502: ws.send('error;remote server error (502)');break;
              case 500: ws.send('error;remote server error (500)');break;
              case 503: ws.send('error;remote server error (503)');break;
              default: ws.send('error;no valid url');break;
            }
          }
        }
        xhr.open('GET', msg[1], true);
        xhr.timeout = 1000;
        xhr.ontimeout = function(e) {ws.send('error;url is to slow')}
        xhr.send();
        setTimeout(to => {if (xhr.readyState !== 4) ws.send('error;url timed out');xhr.abort()}, 1500)
      }
    }
  })
  ws.send('websocket connected')
})

//random key
const forbidden_array = ['sym', 'admin', 'stats']
function get_key(length) {
  let forbidden = false; let output = ''
  let characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'
  do{
    for (let i = 0; i < length; i++ )
      output += characters.charAt(Math.floor(Math.random() * characters.length))
    for (let i = 0; i < forbidden_array.length; i++) if (output === forbidden_array[i]) forbidden = true
    redis_cli.hget("surl;"+output, "url", function(err, obj) {
      if(err) console.log(err)
      if(obj) forbidden = true
    })
  } while (forbidden)
  return output
}