neko/src/component/utils/reconnector.ts

import EventEmitter from 'eventemitter3'
import { ReconnectorConfig } from '../types/reconnector'

export interface ReconnectorAbstractEvents {
  connect: () => void
  disconnect: (error?: Error) => void
}

export abstract class ReconnectorAbstract extends EventEmitter<ReconnectorAbstractEvents> {
  constructor() {
    super()

    if (this.constructor == ReconnectorAbstract) {
      throw new Error("Abstract classes can't be instantiated.")
    }
  }

  public abstract get connected(): boolean

  public abstract connect(): void
  public abstract disconnect(): void
  public abstract destroy(): void
}

export interface ReconnectorEvents {
  open: () => void
  connect: () => void
  disconnect: () => void
  close: (error?: Error) => void
}

export class Reconnector extends EventEmitter<ReconnectorEvents> {
  private _conn: ReconnectorAbstract
  private _config: ReconnectorConfig
  private _timeout?: number

  private _open = false
  private _total_reconnects = 0
  private _last_connected?: Date

  private _onConnectHandle: () => void
  private _onDisconnectHandle: (error?: Error) => void

  constructor(conn: ReconnectorAbstract, config?: ReconnectorConfig) {
    super()

    this._conn = conn
    this._config = {
      maxReconnects: 10,
      timeoutMs: 1500,
      backoffMs: 750,
      ...config,
    }

    this._onConnectHandle = this.onConnect.bind(this)
    this._conn.on('connect', this._onConnectHandle)

    this._onDisconnectHandle = this.onDisconnect.bind(this)
    this._conn.on('disconnect', this._onDisconnectHandle)
  }

  private onConnect() {
    if (this._timeout) {
      window.clearTimeout(this._timeout)
      this._timeout = undefined
    }

    if (this._open) {
      this._last_connected = new Date()
      this.emit('connect')
    } else {
      this._conn.disconnect()
    }
  }

  private onDisconnect() {
    if (this._timeout) {
      window.clearTimeout(this._timeout)
      this._timeout = undefined
    }

    if (this._open) {
      this.emit('disconnect')
      this.reconnect()
    }
  }

  public get isOpen(): boolean {
    return this._open
  }

  public get isConnected(): boolean {
    return this._conn.connected
  }

  public get totalReconnects(): number {
    return this._total_reconnects
  }

  public get lastConnected(): Date | undefined {
    return this._last_connected
  }

  public get config(): ReconnectorConfig {
    return { ...this._config }
  }

  public set config(conf: ReconnectorConfig) {
    this._config = { ...conf }

    if (this._config.maxReconnects > this._total_reconnects) {
      this.close(new Error('reconnection config changed'))
    }
  }

  public open(deferredConnection = false): void {
    if (this._timeout) {
      window.clearTimeout(this._timeout)
      this._timeout = undefined
    }

    if (!this._open) {
      this._open = true
      this.emit('open')
    }

    if (!deferredConnection && !this._conn.connected) {
      this.connect()
    }
  }

  public close(error?: Error): void {
    if (this._timeout) {
      window.clearTimeout(this._timeout)
      this._timeout = undefined
    }

    if (this._open) {
      this._open = false
      this._last_connected = undefined
      this.emit('close', error)
    }

    if (this._conn.connected) {
      this._conn.disconnect()
    }
  }

  public connect(): void {
    if (this._timeout) {
      window.clearTimeout(this._timeout)
      this._timeout = undefined
    }

    this._conn.connect()
    this._timeout = window.setTimeout(this.onDisconnect.bind(this), this._config.timeoutMs)
  }

  public reconnect(): void {
    if (this._timeout) {
      window.clearTimeout(this._timeout)
      this._timeout = undefined
    }

    this._total_reconnects++

    if (this._config.maxReconnects > this._total_reconnects || this._total_reconnects < 0) {
      this._timeout = window.setTimeout(this.connect.bind(this), this._config.backoffMs)
    } else {
      this.close(new Error('reconnection failed'))
    }
  }

  public destroy() {
    if (this._timeout) {
      window.clearTimeout(this._timeout)
      this._timeout = undefined
    }

    this._conn.off('connect', this._onConnectHandle)
    this._conn.off('disconnect', this._onDisconnectHandle)
    this._conn.destroy()
  }
}