example-log-transport.js

import * as Rx from 'rxjs'
import * as ops from 'rxjs/operators'
import fs from 'fs'
import VError from 'verror'
/**
 * for now, there can only be one transport at a time
 * the cli will have to handle an option to directly log to terminal while also including a
 * "terminal ui" output default (progress bars, queued, in progress, completed, etc)
 * this can be accomplished by log options being done directly as command line args
 */
abstract class LogTransport {
  abstract transport: (data: string) => void
}
class StdoutTransport extends LogTransport {
  transport = console.log
}
class FileTransport extends LogTransport {
  writeStream: fs.WriteStream
  constructor(filename: string) {
    super()
    this.writeStream = fs.createWriteStream(filename)
    this.writeStream.on('error', error => {
      throw new VError(error, 'logger file transport')
    })
  }
  transport = (data: string) => {
    this.writeStream.write(data)
  }
}