index.js

const chalk = require('chalk')
const InputPrompt = require('inquirer/lib/prompts/input')
const isFunction = require('lodash.isfunction')
const partialRight = require('lodash.partialright')

const identity = i => i

class MaxLengthInputPrompt extends InputPrompt {
  constructor(...args) {
    super(...args)

    if (!this.opt.maxLength) {
      this.throwParamError('maxLength')
    }

    this.opt.validate = this.createValidator(this.opt.validate)
  }

  measureInput(input) {
    const { filter } = this.opt

    return filter(input, this.answers)
  }

  render(error) {
    const { maxLength, transformer } = this.opt
    const answered = this.status === 'answered'
    const transform = partialRight(
      isFunction(transformer) ? transformer : identity,
      this.answers
    )

    let bottomContent = ''
    let message = this.getQuestion()
    const { length } = this.measureInput(this.rl.line)

    if (answered) {
      message += chalk.cyan(this.answer)
    } else {
      message += transform(this.rl.line)
    }

    if (error) {
      bottomContent = chalk.red('>> ') + error
    } else if (!answered) {
      const percent = length / maxLength * 100
      const color =
        percent < 80 ? chalk.green : percent > 100 ? chalk.red : chalk.yellow

      bottomContent = `(${color(length)}/${this.opt.maxLength} characters)`
    }

    this.screen.render(message, bottomContent)
  }

  createValidator(validate) {
    const { filter, maxLength } = this.opt

    return (...args) => {
      const [input, answers] = args
      const didInput =
        (input && !filter) || (input && filter('', answers) !== input)

      const { length } = input

      if (length > maxLength) {
        this.rl.line = this.rl.history[0]
        this.rl.cursor = this.rl.line.length
        return this.constructor.VALIDATION_ERROR_MESSAGE
      }

      return validate(...args, didInput ? this.rl.history[0] : '')
    }
  }
}

MaxLengthInputPrompt.VALIDATION_ERROR_MESSAGE =
  'Input contains too many characters!'

module.exports = MaxLengthInputPrompt