// Port of python's argparse module, version 3.9.0:
// https://github.com/python/cpython/blob/v3.9.0rc1/Lib/argparse.py

'use strict'

// Copyright (C) 2010-2020 Python Software Foundation.
// Copyright (C) 2020 argparse.js authors

/*
 * Command-line parsing library
 *
 * This module is an optparse-inspired command-line parsing library that:
 *
 *     - handles both optional and positional arguments
 *     - produces highly informative usage messages
 *     - supports parsers that dispatch to sub-parsers
 *
 * The following is a simple usage example that sums integers from the
 * command-line and writes the result to a file::
 *
 *     parser = argparse.ArgumentParser(
 *         description='sum the integers at the command line')
 *     parser.add_argument(
 *         'integers', metavar='int', nargs='+', type=int,
 *         help='an integer to be summed')
 *     parser.add_argument(
 *         '--log', default=sys.stdout, type=argparse.FileType('w'),
 *         help='the file where the sum should be written')
 *     args = parser.parse_args()
 *     args.log.write('%s' % sum(args.integers))
 *     args.log.close()
 *
 * The module contains the following public classes:
 *
 *     - ArgumentParser -- The main entry point for command-line parsing. As the
 *         example above shows, the add_argument() method is used to populate
 *         the parser with actions for optional and positional arguments. Then
 *         the parse_args() method is invoked to convert the args at the
 *         command-line into an object with attributes.
 *
 *     - ArgumentError -- The exception raised by ArgumentParser objects when
 *         there are errors with the parser's actions. Errors raised while
 *         parsing the command-line are caught by ArgumentParser and emitted
 *         as command-line messages.
 *
 *     - FileType -- A factory for defining types of files to be created. As the
 *         example above shows, instances of FileType are typically passed as
 *         the type= argument of add_argument() calls.
 *
 *     - Action -- The base class for parser actions. Typically actions are
 *         selected by passing strings like 'store_true' or 'append_const' to
 *         the action= argument of add_argument(). However, for greater
 *         customization of ArgumentParser actions, subclasses of Action may
 *         be defined and passed as the action= argument.
 *
 *     - HelpFormatter, RawDescriptionHelpFormatter, RawTextHelpFormatter,
 *         ArgumentDefaultsHelpFormatter -- Formatter classes which
 *         may be passed as the formatter_class= argument to the
 *         ArgumentParser constructor. HelpFormatter is the default,
 *         RawDescriptionHelpFormatter and RawTextHelpFormatter tell the parser
 *         not to change the formatting for help text, and
 *         ArgumentDefaultsHelpFormatter adds information about argument defaults
 *         to the help.
 *
 * All other classes in this module are considered implementation details.
 * (Also note that HelpFormatter and RawDescriptionHelpFormatter are only
 * considered public as object names -- the API of the formatter objects is
 * still considered an implementation detail.)
 */

const SUPPRESS = '==SUPPRESS=='

const OPTIONAL = '?'
const ZERO_OR_MORE = '*'
const ONE_OR_MORE = '+'
const PARSER = 'A...'
const REMAINDER = '...'
const _UNRECOGNIZED_ARGS_ATTR = '_unrecognized_args'


// ==================================
// Utility functions used for porting
// ==================================
const assert = require('assert')
const util = require('util')
const fs = require('fs')
const sub = require('./lib/sub')
const path = require('path')
const repr = util.inspect

function get_argv() {
    // omit first argument (which is assumed to be interpreter - `node`, `coffee`, `ts-node`, etc.)
    return process.argv.slice(1)
}

function get_terminal_size() {
    return {
        columns: +process.env.COLUMNS || process.stdout.columns || 80
    }
}

function hasattr(object, name) {
    return Object.prototype.hasOwnProperty.call(object, name)
}

function getattr(object, name, value) {
    return hasattr(object, name) ? object[name] : value
}

function setattr(object, name, value) {
    object[name] = value
}

function setdefault(object, name, value) {
    if (!hasattr(object, name)) object[name] = value
    return object[name]
}

function delattr(object, name) {
    delete object[name]
}

function range(from, to, step=1) {
    // range(10) is equivalent to range(0, 10)
    if (arguments.length === 1) [ to, from ] = [ from, 0 ]
    if (typeof from !== 'number' || typeof to !== 'number' || typeof step !== 'number') {
        throw new TypeError('argument cannot be interpreted as an integer')
    }
    if (step === 0) throw new TypeError('range() arg 3 must not be zero')

    let result = []
    if (step > 0) {
        for (let i = from; i < to; i += step) result.push(i)
    } else {
        for (let i = from; i > to; i += step) result.push(i)
    }
    return result
}

function splitlines(str, keepends = false) {
    let result
    if (!keepends) {
        result = str.split(/\r\n|[\n\r\v\f\x1c\x1d\x1e\x85\u2028\u2029]/)
    } else {
        result = []
        let parts = str.split(/(\r\n|[\n\r\v\f\x1c\x1d\x1e\x85\u2028\u2029])/)
        for (let i = 0; i < parts.length; i += 2) {
            result.push(parts[i] + (i + 1 < parts.length ? parts[i + 1] : ''))
        }
    }
    if (!result[result.length - 1]) result.pop()
    return result
}

function _string_lstrip(string, prefix_chars) {
    let idx = 0
    while (idx < string.length && prefix_chars.includes(string[idx])) idx++
    return idx ? string.slice(idx) : string
}

function _string_split(string, sep, maxsplit) {
    let result = string.split(sep)
    if (result.length > maxsplit) {
        result = result.slice(0, maxsplit).concat([ result.slice(maxsplit).join(sep) ])
    }
    return result
}

function _array_equal(array1, array2) {
    if (array1.length !== array2.length) return false
    for (let i = 0; i < array1.length; i++) {
        if (array1[i] !== array2[i]) return false
    }
    return true
}

function _array_remove(array, item) {
    let idx = array.indexOf(item)
    if (idx === -1) throw new TypeError(sub('%r not in list', item))
    array.splice(idx, 1)
}

// normalize choices to array;
// this isn't required in python because `in` and `map` operators work with anything,
// but in js dealing with multiple types here is too clunky
function _choices_to_array(choices) {
    if (choices === undefined) {
        return []
    } else if (Array.isArray(choices)) {
        return choices
    } else if (choices !== null && typeof choices[Symbol.iterator] === 'function') {
        return Array.from(choices)
    } else if (typeof choices === 'object' && choices !== null) {
        return Object.keys(choices)
    } else {
        throw new Error(sub('invalid choices value: %r', choices))
    }
}

// decorator that allows a class to be called without new
function _callable(cls) {
    let result = { // object is needed for inferred class name
        [cls.name]: function (...args) {
            let this_class = new.target === result || !new.target
            return Reflect.construct(cls, args, this_class ? cls : new.target)
        }
    }
    result[cls.name].prototype = cls.prototype
    // fix default tag for toString, e.g. [object Action] instead of [object Object]
    cls.prototype[Symbol.toStringTag] = cls.name
    return result[cls.name]
}

function _alias(object, from, to) {
    try {
        let name = object.constructor.name
        Object.defineProperty(object, from, {
            value: util.deprecate(object[to], sub('%s.%s() is renamed to %s.%s()',
                name, from, name, to)),
            enumerable: false
        })
    } catch {}
}

// decorator that allows snake_case class methods to be called with camelCase and vice versa
function _camelcase_alias(_class) {
    for (let name of Object.getOwnPropertyNames(_class.prototype)) {
        let camelcase = name.replace(/\w_[a-z]/g, s => s[0] + s[2].toUpperCase())
        if (camelcase !== name) _alias(_class.prototype, camelcase, name)
    }
    return _class
}

function _to_legacy_name(key) {
    key = key.replace(/\w_[a-z]/g, s => s[0] + s[2].toUpperCase())
    if (key === 'default') key = 'defaultValue'
    if (key === 'const') key = 'constant'
    return key
}

function _to_new_name(key) {
    if (key === 'defaultValue') key = 'default'
    if (key === 'constant') key = 'const'
    key = key.replace(/[A-Z]/g, c => '_' + c.toLowerCase())
    return key
}

// parse options
let no_default = Symbol('no_default_value')
function _parse_opts(args, descriptor) {
    function get_name() {
        let stack = new Error().stack.split('\n')
            .map(x => x.match(/^    at (.*) \(.*\)$/))
            .filter(Boolean)
            .map(m => m[1])
            .map(fn => fn.match(/[^ .]*$/)[0])

        if (stack.length && stack[0] === get_name.name) stack.shift()
        if (stack.length && stack[0] === _parse_opts.name) stack.shift()
        return stack.length ? stack[0] : ''
    }

    args = Array.from(args)
    let kwargs = {}
    let result = []
    let last_opt = args.length && args[args.length - 1]

    if (typeof last_opt === 'object' && last_opt !== null && !Array.isArray(last_opt) &&
        (!last_opt.constructor || last_opt.constructor.name === 'Object')) {
        kwargs = Object.assign({}, args.pop())
    }

    // LEGACY (v1 compatibility): camelcase
    let renames = []
    for (let key of Object.keys(descriptor)) {
        let old_name = _to_legacy_name(key)
        if (old_name !== key && (old_name in kwargs)) {
            if (key in kwargs) {
                // default and defaultValue specified at the same time, happens often in old tests
                //throw new TypeError(sub('%s() got multiple values for argument %r', get_name(), key))
            } else {
                kwargs[key] = kwargs[old_name]
            }
            renames.push([ old_name, key ])
            delete kwargs[old_name]
        }
    }
    if (renames.length) {
        let name = get_name()
        deprecate('camelcase_' + name, sub('%s(): following options are renamed: %s',
            name, renames.map(([ a, b ]) => sub('%r -> %r', a, b))))
    }
    // end

    let missing_positionals = []
    let positional_count = args.length

    for (let [ key, def ] of Object.entries(descriptor)) {
        if (key[0] === '*') {
            if (key.length > 0 && key[1] === '*') {
                // LEGACY (v1 compatibility): camelcase
                let renames = []
                for (let key of Object.keys(kwargs)) {
                    let new_name = _to_new_name(key)
                    if (new_name !== key && (key in kwargs)) {
                        if (new_name in kwargs) {
                            // default and defaultValue specified at the same time, happens often in old tests
                            //throw new TypeError(sub('%s() got multiple values for argument %r', get_name(), new_name))
                        } else {
                            kwargs[new_name] = kwargs[key]
                        }
                        renames.push([ key, new_name ])
                        delete kwargs[key]
                    }
                }
                if (renames.length) {
                    let name = get_name()
                    deprecate('camelcase_' + name, sub('%s(): following options are renamed: %s',
                        name, renames.map(([ a, b ]) => sub('%r -> %r', a, b))))
                }
                // end
                result.push(kwargs)
                kwargs = {}
            } else {
                result.push(args)
                args = []
            }
        } else if (key in kwargs && args.length > 0) {
            throw new TypeError(sub('%s() got multiple values for argument %r', get_name(), key))
        } else if (key in kwargs) {
            result.push(kwargs[key])
            delete kwargs[key]
        } else if (args.length > 0) {
            result.push(args.shift())
        } else if (def !== no_default) {
            result.push(def)
        } else {
            missing_positionals.push(key)
        }
    }

    if (Object.keys(kwargs).length) {
        throw new TypeError(sub('%s() got an unexpected keyword argument %r',
            get_name(), Object.keys(kwargs)[0]))
    }

    if (args.length) {
        let from = Object.entries(descriptor).filter(([ k, v ]) => k[0] !== '*' && v !== no_default).length
        let to = Object.entries(descriptor).filter(([ k ]) => k[0] !== '*').length
        throw new TypeError(sub('%s() takes %s positional argument%s but %s %s given',
            get_name(),
            from === to ? sub('from %s to %s', from, to) : to,
            from === to && to === 1 ? '' : 's',
            positional_count,
            positional_count === 1 ? 'was' : 'were'))
    }

    if (missing_positionals.length) {
        let strs = missing_positionals.map(repr)
        if (strs.length > 1) strs[strs.length - 1] = 'and ' + strs[strs.length - 1]
        let str_joined = strs.join(strs.length === 2 ? '' : ', ')
        throw new TypeError(sub('%s() missing %i required positional argument%s: %s',
            get_name(), strs.length, strs.length === 1 ? '' : 's', str_joined))
    }

    return result
}

let _deprecations = {}
function deprecate(id, string) {
    _deprecations[id] = _deprecations[id] || util.deprecate(() => {}, string)
    _deprecations[id]()
}


// =============================
// Utility functions and classes
// =============================
function _AttributeHolder(cls = Object) {
    /*
     *  Abstract base class that provides __repr__.
     *
     *  The __repr__ method returns a string in the format::
     *      ClassName(attr=name, attr=name, ...)
     *  The attributes are determined either by a class-level attribute,
     *  '_kwarg_names', or by inspecting the instance __dict__.
     */

    return class _AttributeHolder extends cls {
        [util.inspect.custom]() {
            let type_name = this.constructor.name
            let arg_strings = []
            let star_args = {}
            for (let arg of this._get_args()) {
                arg_strings.push(repr(arg))
            }
            for (let [ name, value ] of this._get_kwargs()) {
                if (/^[a-z_][a-z0-9_$]*$/i.test(name)) {
                    arg_strings.push(sub('%s=%r', name, value))
                } else {
                    star_args[name] = value
                }
            }
            if (Object.keys(star_args).length) {
                arg_strings.push(sub('**%s', repr(star_args)))
            }
            return sub('%s(%s)', type_name, arg_strings.join(', '))
        }

        toString() {
            return this[util.inspect.custom]()
        }

        _get_kwargs() {
            return Object.entries(this)
        }

        _get_args() {
            return []
        }
    }
}


function _copy_items(items) {
    if (items === undefined) {
        return []
    }
    return items.slice(0)
}


// ===============
// Formatting Help
// ===============
const HelpFormatter = _camelcase_alias(_callable(class HelpFormatter {
    /*
     *  Formatter for generating usage messages and argument help strings.
     *
     *  Only the name of this class is considered a public API. All the methods
     *  provided by the class are considered an implementation detail.
     */

    constructor() {
        let [
            prog,
            indent_increment,
            max_help_position,
            width
        ] = _parse_opts(arguments, {
            prog: no_default,
            indent_increment: 2,
            max_help_position: 24,
            width: undefined
        })

        // default setting for width
        if (width === undefined) {
            width = get_terminal_size().columns
            width -= 2
        }

        this._prog = prog
        this._indent_increment = indent_increment
        this._max_help_position = Math.min(max_help_position,
                                      Math.max(width - 20, indent_increment * 2))
        this._width = width

        this._current_indent = 0
        this._level = 0
        this._action_max_length = 0

        this._root_section = this._Section(this, undefined)
        this._current_section = this._root_section

        this._whitespace_matcher = /[ \t\n\r\f\v]+/g // equivalent to python /\s+/ with ASCII flag
        this._long_break_matcher = /\n\n\n+/g
    }

    // ===============================
    // Section and indentation methods
    // ===============================
    _indent() {
        this._current_indent += this._indent_increment
        this._level += 1
    }

    _dedent() {
        this._current_indent -= this._indent_increment
        assert(this._current_indent >= 0, 'Indent decreased below 0.')
        this._level -= 1
    }

    _add_item(func, args) {
        this._current_section.items.push([ func, args ])
    }

    // ========================
    // Message building methods
    // ========================
    start_section(heading) {
        this._indent()
        let section = this._Section(this, this._current_section, heading)
        this._add_item(section.format_help.bind(section), [])
        this._current_section = section
    }

    end_section() {
        this._current_section = this._current_section.parent
        this._dedent()
    }

    add_text(text) {
        if (text !== SUPPRESS && text !== undefined) {
            this._add_item(this._format_text.bind(this), [text])
        }
    }

    add_usage(usage, actions, groups, prefix = undefined) {
        if (usage !== SUPPRESS) {
            let args = [ usage, actions, groups, prefix ]
            this._add_item(this._format_usage.bind(this), args)
        }
    }

    add_argument(action) {
        if (action.help !== SUPPRESS) {

            // find all invocations
            let invocations = [this._format_action_invocation(action)]
            for (let subaction of this._iter_indented_subactions(action)) {
                invocations.push(this._format_action_invocation(subaction))
            }

            // update the maximum item length
            let invocation_length = Math.max(...invocations.map(invocation => invocation.length))
            let action_length = invocation_length + this._current_indent
            this._action_max_length = Math.max(this._action_max_length,
                                               action_length)

            // add the item to the list
            this._add_item(this._format_action.bind(this), [action])
        }
    }

    add_arguments(actions) {
        for (let action of actions) {
            this.add_argument(action)
        }
    }

    // =======================
    // Help-formatting methods
    // =======================
    format_help() {
        let help = this._root_section.format_help()
        if (help) {
            help = help.replace(this._long_break_matcher, '\n\n')
            help = help.replace(/^\n+|\n+$/g, '') + '\n'
        }
        return help
    }

    _join_parts(part_strings) {
        return part_strings.filter(part => part && part !== SUPPRESS).join('')
    }

    _format_usage(usage, actions, groups, prefix) {
        if (prefix === undefined) {
            prefix = 'usage: '
        }

        // if usage is specified, use that
        if (usage !== undefined) {
            usage = sub(usage, { prog: this._prog })

        // if no optionals or positionals are available, usage is just prog
        } else if (usage === undefined && !actions.length) {
            usage = sub('%(prog)s', { prog: this._prog })

        // if optionals and positionals are available, calculate usage
        } else if (usage === undefined) {
            let prog = sub('%(prog)s', { prog: this._prog })

            // split optionals from positionals
            let optionals = []
            let positionals = []
            for (let action of actions) {
                if (action.option_strings.length) {
                    optionals.push(action)
                } else {
                    positionals.push(action)
                }
            }

            // build full usage string
            let action_usage = this._format_actions_usage([].concat(optionals).concat(positionals), groups)
            usage = [ prog, action_usage ].map(String).join(' ')

            // wrap the usage parts if it's too long
            let text_width = this._width - this._current_indent
            if (prefix.length + usage.length > text_width) {

                // break usage into wrappable parts
                let part_regexp = /\(.*?\)+(?=\s|$)|\[.*?\]+(?=\s|$)|\S+/g
                let opt_usage = this._format_actions_usage(optionals, groups)
                let pos_usage = this._format_actions_usage(positionals, groups)
                let opt_parts = opt_usage.match(part_regexp) || []
                let pos_parts = pos_usage.match(part_regexp) || []
                assert(opt_parts.join(' ') === opt_usage)
                assert(pos_parts.join(' ') === pos_usage)

                // helper for wrapping lines
                let get_lines = (parts, indent, prefix = undefined) => {
                    let lines = []
                    let line = []
                    let line_len
                    if (prefix !== undefined) {
                        line_len = prefix.length - 1
                    } else {
                        line_len = indent.length - 1
                    }
                    for (let part of parts) {
                        if (line_len + 1 + part.length > text_width && line) {
                            lines.push(indent + line.join(' '))
                            line = []
                            line_len = indent.length - 1
                        }
                        line.push(part)
                        line_len += part.length + 1
                    }
                    if (line.length) {
                        lines.push(indent + line.join(' '))
                    }
                    if (prefix !== undefined) {
                        lines[0] = lines[0].slice(indent.length)
                    }
                    return lines
                }

                let lines

                // if prog is short, follow it with optionals or positionals
                if (prefix.length + prog.length <= 0.75 * text_width) {
                    let indent = ' '.repeat(prefix.length + prog.length + 1)
                    if (opt_parts.length) {
                        lines = get_lines([prog].concat(opt_parts), indent, prefix)
                        lines = lines.concat(get_lines(pos_parts, indent))
                    } else if (pos_parts.length) {
                        lines = get_lines([prog].concat(pos_parts), indent, prefix)
                    } else {
                        lines = [prog]
                    }

                // if prog is long, put it on its own line
                } else {
                    let indent = ' '.repeat(prefix.length)
                    let parts = [].concat(opt_parts).concat(pos_parts)
                    lines = get_lines(parts, indent)
                    if (lines.length > 1) {
                        lines = []
                        lines = lines.concat(get_lines(opt_parts, indent))
                        lines = lines.concat(get_lines(pos_parts, indent))
                    }
                    lines = [prog].concat(lines)
                }

                // join lines into usage
                usage = lines.join('\n')
            }
        }

        // prefix with 'usage:'
        return sub('%s%s\n\n', prefix, usage)
    }

    _format_actions_usage(actions, groups) {
        // find group indices and identify actions in groups
        let group_actions = new Set()
        let inserts = {}
        for (let group of groups) {
            let start = actions.indexOf(group._group_actions[0])
            if (start === -1) {
                continue
            } else {
                let end = start + group._group_actions.length
                if (_array_equal(actions.slice(start, end), group._group_actions)) {
                    for (let action of group._group_actions) {
                        group_actions.add(action)
                    }
                    if (!group.required) {
                        if (start in inserts) {
                            inserts[start] += ' ['
                        } else {
                            inserts[start] = '['
                        }
                        if (end in inserts) {
                            inserts[end] += ']'
                        } else {
                            inserts[end] = ']'
                        }
                    } else {
                        if (start in inserts) {
                            inserts[start] += ' ('
                        } else {
                            inserts[start] = '('
                        }
                        if (end in inserts) {
                            inserts[end] += ')'
                        } else {
                            inserts[end] = ')'
                        }
                    }
                    for (let i of range(start + 1, end)) {
                        inserts[i] = '|'
                    }
                }
            }
        }

        // collect all actions format strings
        let parts = []
        for (let [ i, action ] of Object.entries(actions)) {

            // suppressed arguments are marked with None
            // remove | separators for suppressed arguments
            if (action.help === SUPPRESS) {
                parts.push(undefined)
                if (inserts[+i] === '|') {
                    delete inserts[+i]
                } else if (inserts[+i + 1] === '|') {
                    delete inserts[+i + 1]
                }

            // produce all arg strings
            } else if (!action.option_strings.length) {
                let default_value = this._get_default_metavar_for_positional(action)
                let part = this._format_args(action, default_value)

                // if it's in a group, strip the outer []
                if (group_actions.has(action)) {
                    if (part[0] === '[' && part[part.length - 1] === ']') {
                        part = part.slice(1, -1)
                    }
                }

                // add the action string to the list
                parts.push(part)

            // produce the first way to invoke the option in brackets
            } else {
                let option_string = action.option_strings[0]
                let part

                // if the Optional doesn't take a value, format is:
                //    -s or --long
                if (action.nargs === 0) {
                    part = action.format_usage()

                // if the Optional takes a value, format is:
                //    -s ARGS or --long ARGS
                } else {
                    let default_value = this._get_default_metavar_for_optional(action)
                    let args_string = this._format_args(action, default_value)
                    part = sub('%s %s', option_string, args_string)
                }

                // make it look optional if it's not required or in a group
                if (!action.required && !group_actions.has(action)) {
                    part = sub('[%s]', part)
                }

                // add the action string to the list
                parts.push(part)
            }
        }

        // insert things at the necessary indices
        for (let i of Object.keys(inserts).map(Number).sort((a, b) => b - a)) {
            parts.splice(+i, 0, inserts[+i])
        }

        // join all the action items with spaces
        let text = parts.filter(Boolean).join(' ')

        // clean up separators for mutually exclusive groups
        text = text.replace(/([\[(]) /g, '$1')
        text = text.replace(/ ([\])])/g, '$1')
        text = text.replace(/[\[(] *[\])]/g, '')
        text = text.replace(/\(([^|]*)\)/g, '$1', text)
        text = text.trim()

        // return the text
        return text
    }

    _format_text(text) {
        if (text.includes('%(prog)')) {
            text = sub(text, { prog: this._prog })
        }
        let text_width = Math.max(this._width - this._current_indent, 11)
        let indent = ' '.repeat(this._current_indent)
        return this._fill_text(text, text_width, indent) + '\n\n'
    }

    _format_action(action) {
        // determine the required width and the entry label
        let help_position = Math.min(this._action_max_length + 2,
                                     this._max_help_position)
        let help_width = Math.max(this._width - help_position, 11)
        let action_width = help_position - this._current_indent - 2
        let action_header = this._format_action_invocation(action)
        let indent_first

        // no help; start on same line and add a final newline
        if (!action.help) {
            let tup = [ this._current_indent, '', action_header ]
            action_header = sub('%*s%s\n', ...tup)

        // short action name; start on the same line and pad two spaces
        } else if (action_header.length <= action_width) {
            let tup = [ this._current_indent, '', action_width, action_header ]
            action_header = sub('%*s%-*s  ', ...tup)
            indent_first = 0

        // long action name; start on the next line
        } else {
            let tup = [ this._current_indent, '', action_header ]
            action_header = sub('%*s%s\n', ...tup)
            indent_first = help_position
        }

        // collect the pieces of the action help
        let parts = [action_header]

        // if there was help for the action, add lines of help text
        if (action.help) {
            let help_text = this._expand_help(action)
            let help_lines = this._split_lines(help_text, help_width)
            parts.push(sub('%*s%s\n', indent_first, '', help_lines[0]))
            for (let line of help_lines.slice(1)) {
                parts.push(sub('%*s%s\n', help_position, '', line))
            }

        // or add a newline if the description doesn't end with one
        } else if (!action_header.endsWith('\n')) {
            parts.push('\n')
        }

        // if there are any sub-actions, add their help as well
        for (let subaction of this._iter_indented_subactions(action)) {
            parts.push(this._format_action(subaction))
        }

        // return a single string
        return this._join_parts(parts)
    }

    _format_action_invocation(action) {
        if (!action.option_strings.length) {
            let default_value = this._get_default_metavar_for_positional(action)
            let metavar = this._metavar_formatter(action, default_value)(1)[0]
            return metavar

        } else {
            let parts = []

            // if the Optional doesn't take a value, format is:
            //    -s, --long
            if (action.nargs === 0) {
                parts = parts.concat(action.option_strings)

            // if the Optional takes a value, format is:
            //    -s ARGS, --long ARGS
            } else {
                let default_value = this._get_default_metavar_for_optional(action)
                let args_string = this._format_args(action, default_value)
                for (let option_string of action.option_strings) {
                    parts.push(sub('%s %s', option_string, args_string))
                }
            }

            return parts.join(', ')
        }
    }

    _metavar_formatter(action, default_metavar) {
        let result
        if (action.metavar !== undefined) {
            result = action.metavar
        } else if (action.choices !== undefined) {
            let choice_strs = _choices_to_array(action.choices).map(String)
            result = sub('{%s}', choice_strs.join(','))
        } else {
            result = default_metavar
        }

        function format(tuple_size) {
            if (Array.isArray(result)) {
                return result
            } else {
                return Array(tuple_size).fill(result)
            }
        }
        return format
    }

    _format_args(action, default_metavar) {
        let get_metavar = this._metavar_formatter(action, default_metavar)
        let result
        if (action.nargs === undefined) {
            result = sub('%s', ...get_metavar(1))
        } else if (action.nargs === OPTIONAL) {
            result = sub('[%s]', ...get_metavar(1))
        } else if (action.nargs === ZERO_OR_MORE) {
            let metavar = get_metavar(1)
            if (metavar.length === 2) {
                result = sub('[%s [%s ...]]', ...metavar)
            } else {
                result = sub('[%s ...]', ...metavar)
            }
        } else if (action.nargs === ONE_OR_MORE) {
            result = sub('%s [%s ...]', ...get_metavar(2))
        } else if (action.nargs === REMAINDER) {
            result = '...'
        } else if (action.nargs === PARSER) {
            result = sub('%s ...', ...get_metavar(1))
        } else if (action.nargs === SUPPRESS) {
            result = ''
        } else {
            let formats
            try {
                formats = range(action.nargs).map(() => '%s')
            } catch (err) {
                throw new TypeError('invalid nargs value')
            }
            result = sub(formats.join(' '), ...get_metavar(action.nargs))
        }
        return result
    }

    _expand_help(action) {
        let params = Object.assign({ prog: this._prog }, action)
        for (let name of Object.keys(params)) {
            if (params[name] === SUPPRESS) {
                delete params[name]
            }
        }
        for (let name of Object.keys(params)) {
            if (params[name] && params[name].name) {
                params[name] = params[name].name
            }
        }
        if (params.choices !== undefined) {
            let choices_str = _choices_to_array(params.choices).map(String).join(', ')
            params.choices = choices_str
        }
        // LEGACY (v1 compatibility): camelcase
        for (let key of Object.keys(params)) {
            let old_name = _to_legacy_name(key)
            if (old_name !== key) {
                params[old_name] = params[key]
            }
        }
        // end
        return sub(this._get_help_string(action), params)
    }

    * _iter_indented_subactions(action) {
        if (typeof action._get_subactions === 'function') {
            this._indent()
            yield* action._get_subactions()
            this._dedent()
        }
    }

    _split_lines(text, width) {
        text = text.replace(this._whitespace_matcher, ' ').trim()
        // The textwrap module is used only for formatting help.
        // Delay its import for speeding up the common usage of argparse.
        let textwrap = require('./lib/textwrap')
        return textwrap.wrap(text, { width })
    }

    _fill_text(text, width, indent) {
        text = text.replace(this._whitespace_matcher, ' ').trim()
        let textwrap = require('./lib/textwrap')
        return textwrap.fill(text, { width,
                                     initial_indent: indent,
                                     subsequent_indent: indent })
    }

    _get_help_string(action) {
        return action.help
    }

    _get_default_metavar_for_optional(action) {
        return action.dest.toUpperCase()
    }

    _get_default_metavar_for_positional(action) {
        return action.dest
    }
}))

HelpFormatter.prototype._Section = _callable(class _Section {

    constructor(formatter, parent, heading = undefined) {
        this.formatter = formatter
        this.parent = parent
        this.heading = heading
        this.items = []
    }

    format_help() {
        // format the indented section
        if (this.parent !== undefined) {
            this.formatter._indent()
        }
        let item_help = this.formatter._join_parts(this.items.map(([ func, args ]) => func.apply(null, args)))
        if (this.parent !== undefined) {
            this.formatter._dedent()
        }

        // return nothing if the section was empty
        if (!item_help) {
            return ''
        }

        // add the heading if the section was non-empty
        let heading
        if (this.heading !== SUPPRESS && this.heading !== undefined) {
            let current_indent = this.formatter._current_indent
            heading = sub('%*s%s:\n', current_indent, '', this.heading)
        } else {
            heading = ''
        }

        // join the section-initial newline, the heading and the help
        return this.formatter._join_parts(['\n', heading, item_help, '\n'])
    }
})


const RawDescriptionHelpFormatter = _camelcase_alias(_callable(class RawDescriptionHelpFormatter extends HelpFormatter {
    /*
     *  Help message formatter which retains any formatting in descriptions.
     *
     *  Only the name of this class is considered a public API. All the methods
     *  provided by the class are considered an implementation detail.
     */

    _fill_text(text, width, indent) {
        return splitlines(text, true).map(line => indent + line).join('')
    }
}))


const RawTextHelpFormatter = _camelcase_alias(_callable(class RawTextHelpFormatter extends RawDescriptionHelpFormatter {
    /*
     *  Help message formatter which retains formatting of all help text.
     *
     *  Only the name of this class is considered a public API. All the methods
     *  provided by the class are considered an implementation detail.
     */

    _split_lines(text/*, width*/) {
        return splitlines(text)
    }
}))


const ArgumentDefaultsHelpFormatter = _camelcase_alias(_callable(class ArgumentDefaultsHelpFormatter extends HelpFormatter {
    /*
     *  Help message formatter which adds default values to argument help.
     *
     *  Only the name of this class is considered a public API. All the methods
     *  provided by the class are considered an implementation detail.
     */

    _get_help_string(action) {
        let help = action.help
        // LEGACY (v1 compatibility): additional check for defaultValue needed
        if (!action.help.includes('%(default)') && !action.help.includes('%(defaultValue)')) {
            if (action.default !== SUPPRESS) {
                let defaulting_nargs = [OPTIONAL, ZERO_OR_MORE]
                if (action.option_strings.length || defaulting_nargs.includes(action.nargs)) {
                    help += ' (default: %(default)s)'
                }
            }
        }
        return help
    }
}))


const MetavarTypeHelpFormatter = _camelcase_alias(_callable(class MetavarTypeHelpFormatter extends HelpFormatter {
    /*
     *  Help message formatter which uses the argument 'type' as the default
     *  metavar value (instead of the argument 'dest')
     *
     *  Only the name of this class is considered a public API. All the methods
     *  provided by the class are considered an implementation detail.
     */

    _get_default_metavar_for_optional(action) {
        return typeof action.type === 'function' ? action.type.name : action.type
    }

    _get_default_metavar_for_positional(action) {
        return typeof action.type === 'function' ? action.type.name : action.type
    }
}))


// =====================
// Options and Arguments
// =====================
function _get_action_name(argument) {
    if (argument === undefined) {
        return undefined
    } else if (argument.option_strings.length) {
        return argument.option_strings.join('/')
    } else if (![ undefined, SUPPRESS ].includes(argument.metavar)) {
        return argument.metavar
    } else if (![ undefined, SUPPRESS ].includes(argument.dest)) {
        return argument.dest
    } else {
        return undefined
    }
}


const ArgumentError = _callable(class ArgumentError extends Error {
    /*
     *  An error from creating or using an argument (optional or positional).
     *
     *  The string value of this exception is the message, augmented with
     *  information about the argument that caused it.
     */

    constructor(argument, message) {
        super()
        this.name = 'ArgumentError'
        this._argument_name = _get_action_name(argument)
        this._message = message
        this.message = this.str()
    }

    str() {
        let format
        if (this._argument_name === undefined) {
            format = '%(message)s'
        } else {
            format = 'argument %(argument_name)s: %(message)s'
        }
        return sub(format, { message: this._message,
                             argument_name: this._argument_name })
    }
})


const ArgumentTypeError = _callable(class ArgumentTypeError extends Error {
    /*
     * An error from trying to convert a command line string to a type.
     */

    constructor(message) {
        super(message)
        this.name = 'ArgumentTypeError'
    }
})


// ==============
// Action classes
// ==============
const Action = _camelcase_alias(_callable(class Action extends _AttributeHolder(Function) {
    /*
     *  Information about how to convert command line strings to Python objects.
     *
     *  Action objects are used by an ArgumentParser to represent the information
     *  needed to parse a single argument from one or more strings from the
     *  command line. The keyword arguments to the Action constructor are also
     *  all attributes of Action instances.
     *
     *  Keyword Arguments:
     *
     *      - option_strings -- A list of command-line option strings which
     *          should be associated with this action.
     *
     *      - dest -- The name of the attribute to hold the created object(s)
     *
     *      - nargs -- The number of command-line arguments that should be
     *          consumed. By default, one argument will be consumed and a single
     *          value will be produced.  Other values include:
     *              - N (an integer) consumes N arguments (and produces a list)
     *              - '?' consumes zero or one arguments
     *              - '*' consumes zero or more arguments (and produces a list)
     *              - '+' consumes one or more arguments (and produces a list)
     *          Note that the difference between the default and nargs=1 is that
     *          with the default, a single value will be produced, while with
     *          nargs=1, a list containing a single value will be produced.
     *
     *      - const -- The value to be produced if the option is specified and the
     *          option uses an action that takes no values.
     *
     *      - default -- The value to be produced if the option is not specified.
     *
     *      - type -- A callable that accepts a single string argument, and
     *          returns the converted value.  The standard Python types str, int,
     *          float, and complex are useful examples of such callables.  If None,
     *          str is used.
     *
     *      - choices -- A container of values that should be allowed. If not None,
     *          after a command-line argument has been converted to the appropriate
     *          type, an exception will be raised if it is not a member of this
     *          collection.
     *
     *      - required -- True if the action must always be specified at the
     *          command line. This is only meaningful for optional command-line
     *          arguments.
     *
     *      - help -- The help string describing the argument.
     *
     *      - metavar -- The name to be used for the option's argument with the
     *          help string. If None, the 'dest' value will be used as the name.
     */

    constructor() {
        let [
            option_strings,
            dest,
            nargs,
            const_value,
            default_value,
            type,
            choices,
            required,
            help,
            metavar
        ] = _parse_opts(arguments, {
            option_strings: no_default,
            dest: no_default,
            nargs: undefined,
            const: undefined,
            default: undefined,
            type: undefined,
            choices: undefined,
            required: false,
            help: undefined,
            metavar: undefined
        })

        // when this class is called as a function, redirect it to .call() method of itself
        super('return arguments.callee.call.apply(arguments.callee, arguments)')

        this.option_strings = option_strings
        this.dest = dest
        this.nargs = nargs
        this.const = const_value
        this.default = default_value
        this.type = type
        this.choices = choices
        this.required = required
        this.help = help
        this.metavar = metavar
    }

    _get_kwargs() {
        let names = [
            'option_strings',
            'dest',
            'nargs',
            'const',
            'default',
            'type',
            'choices',
            'help',
            'metavar'
        ]
        return names.map(name => [ name, getattr(this, name) ])
    }

    format_usage() {
        return this.option_strings[0]
    }

    call(/*parser, namespace, values, option_string = undefined*/) {
        throw new Error('.call() not defined')
    }
}))


const BooleanOptionalAction = _camelcase_alias(_callable(class BooleanOptionalAction extends Action {

    constructor() {
        let [
            option_strings,
            dest,
            default_value,
            type,
            choices,
            required,
            help,
            metavar
        ] = _parse_opts(arguments, {
            option_strings: no_default,
            dest: no_default,
            default: undefined,
            type: undefined,
            choices: undefined,
            required: false,
            help: undefined,
            metavar: undefined
        })

        let _option_strings = []
        for (let option_string of option_strings) {
            _option_strings.push(option_string)

            if (option_string.startsWith('--')) {
                option_string = '--no-' + option_string.slice(2)
                _option_strings.push(option_string)
            }
        }

        if (help !== undefined && default_value !== undefined) {
            help += ` (default: ${default_value})`
        }

        super({
            option_strings: _option_strings,
            dest,
            nargs: 0,
            default: default_value,
            type,
            choices,
            required,
            help,
            metavar
        })
    }

    call(parser, namespace, values, option_string = undefined) {
        if (this.option_strings.includes(option_string)) {
            setattr(namespace, this.dest, !option_string.startsWith('--no-'))
        }
    }

    format_usage() {
        return this.option_strings.join(' | ')
    }
}))


const _StoreAction = _callable(class _StoreAction extends Action {

    constructor() {
        let [
            option_strings,
            dest,
            nargs,
            const_value,
            default_value,
            type,
            choices,
            required,
            help,
            metavar
        ] = _parse_opts(arguments, {
            option_strings: no_default,
            dest: no_default,
            nargs: undefined,
            const: undefined,
            default: undefined,
            type: undefined,
            choices: undefined,
            required: false,
            help: undefined,
            metavar: undefined
        })

        if (nargs === 0) {
            throw new TypeError('nargs for store actions must be != 0; if you ' +
                        'have nothing to store, actions such as store ' +
                        'true or store const may be more appropriate')
        }
        if (const_value !== undefined && nargs !== OPTIONAL) {
            throw new TypeError(sub('nargs must be %r to supply const', OPTIONAL))
        }
        super({
            option_strings,
            dest,
            nargs,
            const: const_value,
            default: default_value,
            type,
            choices,
            required,
            help,
            metavar
        })
    }

    call(parser, namespace, values/*, option_string = undefined*/) {
        setattr(namespace, this.dest, values)
    }
})


const _StoreConstAction = _callable(class _StoreConstAction extends Action {

    constructor() {
        let [
            option_strings,
            dest,
            const_value,
            default_value,
            required,
            help
            //, metavar
        ] = _parse_opts(arguments, {
            option_strings: no_default,
            dest: no_default,
            const: no_default,
            default: undefined,
            required: false,
            help: undefined,
            metavar: undefined
        })

        super({
            option_strings,
            dest,
            nargs: 0,
            const: const_value,
            default: default_value,
            required,
            help
        })
    }

    call(parser, namespace/*, values, option_string = undefined*/) {
        setattr(namespace, this.dest, this.const)
    }
})


const _StoreTrueAction = _callable(class _StoreTrueAction extends _StoreConstAction {

    constructor() {
        let [
            option_strings,
            dest,
            default_value,
            required,
            help
        ] = _parse_opts(arguments, {
            option_strings: no_default,
            dest: no_default,
            default: false,
            required: false,
            help: undefined
        })

        super({
            option_strings,
            dest,
            const: true,
            default: default_value,
            required,
            help
        })
    }
})


const _StoreFalseAction = _callable(class _StoreFalseAction extends _StoreConstAction {

    constructor() {
        let [
            option_strings,
            dest,
            default_value,
            required,
            help
        ] = _parse_opts(arguments, {
            option_strings: no_default,
            dest: no_default,
            default: true,
            required: false,
            help: undefined
        })

        super({
            option_strings,
            dest,
            const: false,
            default: default_value,
            required,
            help
        })
    }
})


const _AppendAction = _callable(class _AppendAction extends Action {

    constructor() {
        let [
            option_strings,
            dest,
            nargs,
            const_value,
            default_value,
            type,
            choices,
            required,
            help,
            metavar
        ] = _parse_opts(arguments, {
            option_strings: no_default,
            dest: no_default,
            nargs: undefined,
            const: undefined,
            default: undefined,
            type: undefined,
            choices: undefined,
            required: false,
            help: undefined,
            metavar: undefined
        })

        if (nargs === 0) {
            throw new TypeError('nargs f