espterm-front-end/jssrc/term_conn.js

/** Handle connections */
window.Conn = function (screen) {
  let ws
  let heartbeatTout
  let pingIv
  let xoff = false
  let autoXoffTout
  let reconTout

  let pageShown = false

  function onOpen (evt) {
    console.log('CONNECTED')
    heartbeat()
    doSend('i')
  }

  function onClose (evt) {
    console.warn('SOCKET CLOSED, code ' + evt.code + '. Reconnecting...')
    clearTimeout(reconTout)
    reconTout = setTimeout(function () {
      init()
    }, 2000)
    // this happens when the buffer gets fucked up via invalid unicode.
    // we basically use polling instead of socket then
  }

  function onMessage (evt) {
    try {
      // . = heartbeat
      switch (evt.data.charAt(0)) {
        case '.':
          // heartbeat, no-op message
          break

        case '-':
          // console.log('xoff');
          xoff = true
          autoXoffTout = setTimeout(function () {
            xoff = false
          }, 250)
          break

        case '+':
          // console.log('xon');
          xoff = false
          clearTimeout(autoXoffTout)
          break

        default:
          screen.load(evt.data)
          if (!pageShown) {
            showPage()
            pageShown = true
          }
          break
      }
      heartbeat()
    } catch (e) {
      console.error(e)
    }
  }

  function canSend () {
    return !xoff
  }

  function doSend (message) {
    if (_demo) {
      console.log('TX: ', message)
      return true // Simulate success
    }
    if (xoff) {
      // TODO queue
      console.log("Can't send, flood control.")
      return false
    }

    if (!ws) return false // for dry testing
    if (ws.readyState !== 1) {
      console.error('Socket not ready')
      return false
    }
    if (typeof message != 'string') {
      message = JSON.stringify(message)
    }
    ws.send(message)
    return true
  }

  function init () {
    if (window._demo) {
      console.log('Demo mode!')
      screen.load(_demo_screen)
      showPage()
      return
    }

    clearTimeout(reconTout)
    clearTimeout(heartbeatTout)

    ws = new WebSocket('ws://' + _root + '/term/update.ws')
    ws.onopen = onOpen
    ws.onclose = onClose
    ws.onmessage = onMessage
    console.log('Opening socket.')
    heartbeat()
  }

  function heartbeat () {
    clearTimeout(heartbeatTout)
    heartbeatTout = setTimeout(heartbeatFail, 2000)
  }

  function heartbeatFail () {
    console.error('Heartbeat lost, probing server...')
    pingIv = setInterval(function () {
      console.log('> ping')
      $.get('http://' + _root + '/system/ping', function (resp, status) {
        if (status === 200) {
          clearInterval(pingIv)
          console.info('Server ready, reloading page...')
          location.reload()
        }
      }, {
        timeout: 100
      })
    }, 1000)
  }

  return {
    ws: null,
    init: init,
    send: doSend,
    canSend: canSend // check flood control
  }
}