import { templateParser, templateFormatter, parseDigit } from 'input-format'

// US phone number template
const TEMPLATE = '(xxx) xxx-xxxx'

// `parse` function parses input text characters one-by-one.
//
// `function parse(character, value) { return character }`
//
// Arguments:
//  * `character` is the currently parsed input text character.
//  * `value` is the parsed value so far.
//
// Returns:
//  * If it returns anything (not `undefined`) then it is appended to the `value`
//
// `parseDigit` is an exported helper `parse` function
// that returns `character` if it's a digit
// (a common case, e.g. phone numbers input).
//
// `templateParser` wrapper is a small helper
// which enhances `parse` function to limit `value` max length
// to the number of "x"-es in the template.
//
const parse = templateParser(TEMPLATE, parseDigit)

// `format` function formats parsed value.
//
// function format(value) { return { text: '(800) 555-3535', template: '(xxx) xxx-xxxx' } }
//
// Arguments:
//  * `value` is the parsed value to be formatted.
//
// Returns `{ text, template }`, where:
//  * `text` is the formatted text
//  * `template` is the template used to format the `text`
//    (can be a partial template or a full template)
//
// If the `value` couldn't be formatted then
// `format()` should just return `undefined`.
//
// `templateFormatter` helper creates a formatter based on a template.
//
const format = templateFormatter(TEMPLATE)

import { ReactInput } from 'input-format'

<ReactInput
  value={this.state.phone}
  onChange={phone => this.setState({ phone })}
  parse={parse}
  format={format}/>

import { InputController } from 'input-format'

const input = document.querySelector('input')

const inputController = new InputController(input, parse, format, onChange)

inputController.onCut(event)
inputController.onPaste(event)
inputController.onChange(event)
inputController.onKeyDown(event)

import { parse, format } from 'input-format'

function parse_digit(character, value)
{
  if (value.length < 10)
  {
    if (character >= '0' && character <= '9')
    {
      return character
    }
  }
}

function format_phone(value)
{
  ...

  // Just as an example of a return value
  return {
    text: '(800) 555-3535',
    template: '(xxx) xxx-xxxx'
  }
}

let value
let text = '(800) 555-3535'
let caret = 4 // before the first zero

{ value, caret } = parse(text, caret, parse_digit)

value === '8005553535'
caret === 2

{ text, caret } = format(value, caret, format_phone)

value === '(800) 555-3535'
caret === 4