/* eslint-env worker */
'use strict'

let eventsPath = null
let port = null
let currentVersionId = null
let eventSource = null

addEventListener('connect', (event) => {
  // Only keep one active port, for whichever tab was last loaded.
  if (port) {
    port.close()
  }
  port = event.ports[0]
  port.addEventListener('message', receiveMessage)
  port.start()
})

const receiveMessage = (event) => {
  if (event.data.type === 'initialize') {
    const givenEventsPath = event.data.eventsPath

    if (givenEventsPath !== eventsPath) {
      if (eventSource) {
        eventSource.close()
      }

      resetConnectTimeout()

      setTimeout(connectToEvents, 0)
    }

    eventsPath = event.data.eventsPath
  }
}

let connectAttempts
let connectTimeoutMs

const resetConnectTimeout = () => {
  connectAttempts = 0
  connectTimeoutMs = 100
}
resetConnectTimeout()

const bumpConnectTimeout = () => {
  connectAttempts++

  if (connectTimeoutMs === 100 && connectAttempts === 20) {
    connectAttempts = 0
    connectTimeoutMs = 300
  } else if (connectTimeoutMs === 300 && connectAttempts === 20) {
    connectAttempts = 0
    connectTimeoutMs = 1000
  } else if (connectTimeoutMs === 1000 && connectAttempts === 20) {
    connectAttempts = 0
    connectTimeoutMs = 3000
  } else if (connectAttempts === 100) {
    // Give up after 5 minutes.
    console.debug(
      '😢 django-browser-reload failed to connect after 5 minutes, shutting down.'
    )
    close()
    return
  }
  if (connectAttempts === 0) {
    console.debug(
      '😅 django-browser-reload EventSource error, retrying every ' +
        connectTimeoutMs +
        'ms'
    )
  }
}

const connectToEvents = () => {
  if (!eventsPath) {
    setTimeout(connectToEvents, connectTimeoutMs)
    return
  }

  eventSource = new EventSource(eventsPath)

  eventSource.addEventListener('open', () => {
    console.debug('😎 django-browser-reload connected')
  })

  eventSource.addEventListener('message', (event) => {
    // Reset connection timeout when receiving a message, as it’s proof that
    // we are actually connected.
    resetConnectTimeout()

    const message = JSON.parse(event.data)

    if (message.type === 'ping') {
      if (currentVersionId !== null && currentVersionId !== message.versionId) {
        console.debug('🔁 django-browser-reload triggering reload.')
        port.postMessage('Reload')
      }

      currentVersionId = message.versionId
    } else if (message.type === 'reload') {
      port.postMessage('Reload')
    }
  })

  eventSource.addEventListener('error', () => {
    eventSource.close()
    eventSource = null
    bumpConnectTimeout()
    setTimeout(connectToEvents, connectTimeoutMs)
  })
}