import { Channel, Connection, connect as amqpConnect } from "amqplib/callback_api";
import { EventEmitter } from "events";
import util = require('util');

const MAX_LISTENERS = 10000;

var debug = util.debuglog("amqptools");

export class ChannelManager extends EventEmitter {
  connectionURI: string;
  channel: Channel;
  channelPromise: Promise<Channel>;
  connection: Connection;
  maxReconnectionAttempts = 100;
  randomReconnectionInterval = true;

  eventListeners: Event

  private connectCallbacks: ((err: Error, channel: Channel) => void)[] = [];
  private connectInProgress: boolean;

  constructor() {
    super();
    this.setMaxListeners(MAX_LISTENERS);
  }

  onConnectionClose = (error) => {
    debug("amqp connection has been closed");
    this.channel = null;
    this.connection = null;
    this.channelPromise = null;
    var reconnections = 0;
    var tryReconnect = () => {
      debug("Reconnection attempt...");
      this.connect((err) => {
        reconnections++;
        if (!err) {
          this.emit("reconnect");
          return debug("Connection has been restored");
        }
        if (reconnections >= this.maxReconnectionAttempts) {
          throw new Error("Fail to establish a connection with rabbitmq");
        }
        var timeout = this.randomReconnectionInterval ? Math.floor(Math.random()*(10-1)) + 1 : 1;
        debug("Next reconnect in %d seconds", timeout);
        setTimeout(tryReconnect, timeout * 1000);
      });
    };
    tryReconnect();
  }

  connect(cb) {
    debug("Connecting to the rabbitmq server")
    if (this.channel) {
      return cb(null, this.channel);
    }

    this.connectCallbacks.push(cb);
    if (this.connectInProgress) return;
    this.connectInProgress = true;

    amqpConnect(this.connectionURI, (err, connection) => {
      if (err) {
        return this.connectRespond(err, null);
      }
      this.connection = connection;
      this.connection.on("close", this.onConnectionClose);
      this.connection.on("error", err => {
        console.error("Received an error with connection to rabbitmq", err)
      });
      this.connection.createChannel((err, channel) => {
        if (err) {
          return this.connectRespond(err, null);
        }
        this.channel = channel;

        this.channel.on('error', err => {
          debug("Got error on channel: ", err.message, " trying to reconnect")
          this.reconnect()
        });

        this.connectRespond(null, this.channel)
      });
    });
  }

  connectRespond(err, channel) {
    this.connectInProgress = false;
    if (err) {
      debug("Fail to connect...", err);
    }
    else {
      debug("Connected");
    }
    this.connectCallbacks.forEach((extraCb) => {
      if (!extraCb) return;
      extraCb(err, channel);
    });
    this.connectCallbacks = [];
  }

  getChannel(): Promise<Channel> {
    return new Promise<Channel>((resolve, reject) => {
      if (this.channel) {
        return resolve(this.channel);
      }
      this.connect((err, channel) => {
        if (err) return reject(err);
        resolve(channel);
      })
    });
  }

  setConnectionURI(uri) {
    this.connectionURI = uri;
  }

  disconnect(final, cb) {
    if (typeof final === 'function') {
      cb = final
      final = false
    }
    debug("Disconnecting from the rabbitmq server")
    if (!this.connection) {
      return cb();
    }
    this.connection.removeListener("close", this.onConnectionClose);
    this.connection.close(() => {
      this.connection = null;
      this.channel = null;
      this.channelPromise = null;

      cb();
    });
  }

  finalize() {
    this.emit("finalize");
  }

  reconnect(cb?) {
    this.disconnect(() => {
      this.connect(cb);
    });
  }
}

export var channelManager = new ChannelManager();