const cli = {
  width: 80,
  _program: {},
  _options: [],
  program: (information = {}) => {
    cli._program = information
    return cli
  },
  option: (flags, addition = {}) => {
    // name or flags - Either a name or a list of option strings, e.g. foo or -f, --foo.
    // dest - The name of the attribute to be added to the object returned by parse_options().

    // nargs - The number of command-line arguments that should be consumed. // N, ?, *, +, REMAINDER
    // action - The basic type of action to be taken when this argument is encountered at the command line. // store, store_true, store_false, append, append_const, count, help, version

    // const - A constant value required by some action and nargs selections. (supporting store_const and append_const action)

    // metavar - A name for the argument in usage messages.
    // help - A brief description of what the argument does.

    // required - Whether or not the command-line option may be omitted (optionals only).
    // default - The value produced if the argument is absent from the command line.
    // type - The type to which the command-line argument should be converted.
    // choices - A container of the allowable values for the argument.

    flags = Array.isArray(flags) ? flags : [flags]
    addition.dest =
      addition.dest ||
      flags
        .slice(-1)[0]
        .toLowerCase()
        .replace(/^-+/, '')
        .replace(/-[a-z]/g, character => character.slice(1).toUpperCase())
    addition.help =
      addition.help ||
      {
        help: 'output usage information',
        version: 'output the version number'
      }[addition.action]
    cli._options.push(
      Object.assign(addition, {
        flags: flags,
        positional: !flags[0].startsWith('-')
      })
    )
    return cli
  },
  parse: argv => {
    const positionals = cli._options
        .map((option, index) => (option.positional ? index : null))
        .filter(index => index !== null),
      optionals = {}
    cli._options.forEach((option, index) =>
      option.positional
        ? null
        : option.flags.forEach(flag => (optionals[flag] = index))
    )

    cli._program.name = cli._program.name || require('path').parse(argv[1]).base
    const args = argv.slice(2).reduce(
      (result, part) =>
        /^-[^-]/.test(part)
          ? result.concat(
              part
                .slice(1)
                .split('')
                .map(string => '-' + string)
            )
          : result.concat(part),
      []
    )

    let pointer = 0
    while (pointer < args.length) {
      let value = null
      const part = args[pointer]
      const index = part.startsWith('-') ? optionals[part] : positionals.shift()
      if (index == undefined)
        part.startsWith('-')
          ? error(`no such option: ${part}`)
          : error(`extra arguments found: ${part}`)
      if (part.startsWith('-')) pointer += 1
      const { action } = cli._options[index]

      if (['help', 'version'].includes(action)) {
        if (action === 'help') help()
        else if (action === 'version') version()
      } else if (['store_true', 'store_false'].includes(action)) {
        value = action === 'store_true'
      } else {
        const gap = args.slice(pointer).findIndex(part => part in optionals)
        const next = gap === -1 ? args.length : pointer + gap
        value = args.slice(pointer, next)
        if (value.length === 0) {
          if (cli._options[index].positional)
            error(`the following arguments are required: ${part}`)
          else if (cli._options[index].nargs === '+')
            error(`argument ${part}: expected at least one argument`)
          else error(`argument ${part}: expected one argument`)
        }
        if (cli._options[index].nargs !== '+') {
          value = value[0]
          pointer += 1
        } else {
          pointer = next
        }
      }
      cli[cli._options[index].dest] = value
    }
    if (positionals.length)
      error(
        `the following arguments are required: ${positionals
          .map(index => cli._options[index].flags[0])
          .join(', ')}`
      )
    // cli._options.forEach(option => console.log(option.dest, cli[option.dest]))
    return cli
  }
}

const pad = length => new Array(length + 1).join(' ')

const usage = () => {
  const options = cli._options.map(option => {
    const flag = option.flags.sort((a, b) => a.length - b.length)[0]
    const name = option.metavar || option.dest
    if (option.positional) {
      if (option.nargs === '+') return `${name} [${name} ...]`
      else return `${name}`
    } else {
      if (
        ['store_true', 'store_false', 'help', 'version'].includes(option.action)
      )
        return `[${flag}]`
      else if (option.nargs === '+') return `[${flag} ${name} [${name} ...]]`
      else return `[${flag} ${name}]`
    }
  })
  const maximum = cli.width
  const title = `usage: ${cli._program.name}`
  const lines = [title]

  options
    .map(name => ' ' + name)
    .forEach(option => {
      lines[lines.length - 1].length + option.length < maximum
        ? (lines[lines.length - 1] += option)
        : lines.push(pad(title.length) + option)
    })
  console.log(lines.join('\n'))
}

const help = () => {
  usage()
  const positionals = cli._options
    .filter(option => option.positional)
    .map(option => [option.metavar || option.dest, option.help])
  const optionals = cli._options
    .filter(option => !option.positional)
    .map(option => {
      const { flags } = option
      const name = option.metavar || option.dest
      let use = ''
      if (
        ['store_true', 'store_false', 'help', 'version'].includes(option.action)
      )
        use = flags.map(flag => `${flag}`).join(', ')
      else if (option.nargs === '+')
        use = flags.map(flag => `${flag} ${name} [${name} ...]`).join(', ')
      else use = flags.map(flag => `${flag} ${name}`).join(', ')
      return [use, option.help]
    })
  let align = Math.max.apply(
    null,
    positionals.concat(optionals).map(option => option[0].length)
  )
  align = align > 30 ? 30 : align
  const rest = cli.width - align - 4
  const publish = option => {
    const slice = string =>
      Array.from(Array(Math.ceil(string.length / rest)).keys())
        .map(index => string.slice(index * rest, (index + 1) * rest))
        .join('\n' + pad(align + 4))
    option[0].length < align
      ? console.log(
          `  ${option[0]}${pad(align - option[0].length)}  ${slice(option[1])}`
        )
      : console.log(`  ${option[0]}\n${pad(align + 4)}${slice(option[1])}`)
  }
  if (positionals.length) console.log('\npositional arguments:')
  positionals.forEach(publish)
  if (optionals.length) console.log('\noptional arguments:')
  optionals.forEach(publish)
  process.exit()
}

const version = () => {
  console.log(cli._program.version)
  process.exit()
}

const error = message => {
  usage()
  console.log(cli._program.name + ':', 'error:', message)
  process.exit(1)
}

module.exports = cli