const net = require('net');
// TODO: must change to read by env
const API_KEY = Buffer.from('AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA');

function frame(msgType, topicStr, bodyBuf) {
  const topic = Buffer.from(topicStr);
  const payloadLen = 1 + 2 + 4 + topic.length + bodyBuf.length;
  const totalBytes = payloadLen + 32;

  const buf = Buffer.alloc(4 + payloadLen + 32);
  buf.writeUInt32BE(totalBytes, 0);
  buf.writeUInt8(msgType, 4);
  buf.writeUInt16BE(topic.length, 5);
  buf.writeUInt32BE(bodyBuf.length, 7);
  topic.copy(buf, 11);
  bodyBuf.copy(buf, 11 + topic.length);
  API_KEY.copy(buf, 4 + payloadLen);
  return buf;
}

class NprocClient {

  MESSAGE_TYPE = {
    SUB: 1,
    UNSUB: 2,
    PUB: 3,
    PING: 4
  };

  constructor(
    addr,
    onConnect,
    onClose
  ){
    let _addr = addr.toString().split(":");

    let host = _addr[0];
    let port = parseInt(_addr[1]);

    this.client = net.createConnection({
      host: host,
      port: port
    }, () => onConnect());
    this.history = [];
    this.acc = Buffer.alloc(0);
    this.client.on('data', chunk => {
      this.acc = Buffer.concat([this.acc, chunk]);
      while(this.acc.length >= 4){
        const total = this.acc.readUInt32BE(0);
        if (this.acc.length < 4 + total) break;
        const frm = this.acc.subarray(0, 4 + total);
        this.acc = this.acc.subarray(4 + total);

        const msgType = frm.readUInt8(4);
        const topicLen = frm.readUInt16BE(5);
        const bodyLen = frm.readUInt32BE(7);
        const topic = frm.subarray(11, 11 + topicLen).toString();
        const body = frm.subarray(11 + topicLen, 11 + topicLen + bodyLen);

        let res = {
          msgType, topic, body: body.toString()
        };
        console.log(`get msg! ${JSON.stringify(res)}`);

        this.history.push(res);
      }
    });
    this.client.on('close', () => onClose());
  }

  subscribe(topic){
    this.client.write(frame(this.MESSAGE_TYPE.SUB, topic, Buffer.alloc(0)));
  }

  publish(topic, payload){
    this.client.write(frame(this.MESSAGE_TYPE.PUB, topic, Buffer.from(JSON.stringify(payload))));
  }

  // TODO: unsub
  // TODO: ping
}

module.exports = {
  NprocClient
};