now-cli/lib/build-logger.js

// Native
const EventEmitter = require('events')

// Packages
const ansi = require('ansi-escapes')
const io = require('socket.io-client')
const chalk = require('chalk')

class Lines {
  constructor(maxLines = 100) {
    this.max = maxLines
    this.buf = []
  }

  write(str) {
    const {max, buf} = this

    if (buf.length === max) {
      process.stdout.write(ansi.eraseLines(max + 1))
      buf.shift()
      buf.forEach(line => console.log(line))
    }

    buf.push(str)
    console.log(str)
  }

  reset() {
    this.buf = []
  }
}

module.exports = class Logger extends EventEmitter {
  constructor(host, {debug = false, quiet = false} = {}) {
    super()
    this.host = host
    this.debug = debug
    this.quiet = quiet

    // readyState
    this.building = false

    this.socket = io(`https://io.now.sh?host=${host}`)
    this.socket.once('error', this.onSocketError.bind(this))
    this.socket.on('state', this.onState.bind(this))
    this.socket.on('logs', this.onLog.bind(this))
    this.socket.on('backend', this.onComplete.bind(this))

    this.lines = new Lines(10)
  }

  onState(state) {
    if (!state.id) {
      console.error('> Deployment not found')
      this.emit('error')
      return
    }

    if (state.error) {
      console.error('> Deployment error')
      this.emit('error')
      return
    }

    if (state.backend) {
      this.onComplete()
      return
    }

    if (state.logs) {
      state.logs.forEach(this.onLog, this)
    }
  }

  onLog(log) {
    if (!this.building) {
      if (!this.quiet) {
        console.log('> Building')
      }
      this.building = true
    }

    if (this.quiet) {
      return
    }

    if (log.type === 'command') {
      console.log(`${chalk.gray('>')} ▲ ${log.data}`)
      this.lines.reset()
    } else if (log.type === 'stderr') {
      log.data.split('\n').forEach(v => {
        if (v.length > 0) {
          console.error(chalk.gray(`> ${v}`))
        }
      })
      this.lines.reset()
    } else if (log.type === 'stdout') {
      log.data.split('\n').forEach(v => {
        if (v.length > 0) {
          this.lines.write(`${chalk.gray('>')} ${v}`)
        }
      })
    }
  }

  onComplete() {
    this.socket.disconnect()

    if (this.building) {
      this.building = false
    }

    this.emit('close')
  }

  onSocketError(err) {
    if (this.debug) {
      console.log('> [debug] Socket error', err.stack)
    }
  }
}