argparse.lua

-- The MIT License (MIT)

-- Copyright (c) 2013 - 2018 Peter Melnichenko
--                      2019 Paul Ouellette

-- Permission is hereby granted, free of charge, to any person obtaining a copy of
-- this software and associated documentation files (the "Software"), to deal in
-- the Software without restriction, including without limitation the rights to
-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
-- the Software, and to permit persons to whom the Software is furnished to do so,
-- subject to the following conditions:

-- The above copyright notice and this permission notice shall be included in all
-- copies or substantial portions of the Software.

-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
-- FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
-- COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
-- IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
-- CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

local function deep_update(t1, t2)
    for k, v in pairs(t2) do
        if type(v) == "table" then
            v = deep_update({}, v)
        end

        t1[k] = v
    end

    return t1
end

-- A property is a tuple {name, callback}.
-- properties.args is number of properties that can be set as arguments
-- when calling an object.
local function class(prototype, properties, parent)
    -- Class is the metatable of its instances.
    local cl = {}
    cl.__index = cl

    if parent then
        cl.__prototype = deep_update(deep_update({}, parent.__prototype), prototype)
    else
        cl.__prototype = prototype
    end

    if properties then
        local names = {}

        -- Create setter methods and fill set of property names.
        for _, property in ipairs(properties) do
            local name, callback = property[1], property[2]

            cl[name] = function(self, value)
                if not callback(self, value) then
                    self["_" .. name] = value
                end

                return self
            end

            names[name] = true
        end

        function cl.__call(self, ...)
            -- When calling an object, if the first argument is a table,
            -- interpret keys as property names, else delegate arguments
            -- to corresponding setters in order.
            local first = ...
            if type(first) == "table" then
                for name, value in pairs(first) do
                    if names[name] then
                        self[name](self, value)
                    end
                end
            else
                local nargs = select("#", ...)

                for i, property in ipairs(properties) do
                    if i > nargs or i > properties.args then
                        break
                    end

                    local arg = select(i, ...)

                    if arg ~= nil then
                        self[property[1]](self, arg)
                    end
                end
            end

            return self
        end
    end

    -- If indexing class fails, fallback to its parent.
    local class_metatable = {}
    class_metatable.__index = parent

    function class_metatable.__call(self, ...)
        -- Calling a class returns its instance.
        -- Arguments are delegated to the instance.
        local object = deep_update({}, self.__prototype)
        setmetatable(object, self)
        return object(...)
    end

    return setmetatable(cl, class_metatable)
end

local function typecheck(name, types, value)
    for _, type_ in ipairs(types) do
        if type(value) == type_ then
            return true
        end
    end

    error(("bad property '%s' (%s expected, got %s)"):format(name, table.concat(types, " or "), type(value)))
end

local function typechecked(name, ...)
    local types = {...}
    return {name, function(_, value) typecheck(name, types, value) end}
end

local multiname = {"name", function(self, value)
    typecheck("name", {"string"}, value)

    for alias in value:gmatch("%S+") do
        self._name = self._name or alias
        table.insert(self._aliases, alias)
        table.insert(self._public_aliases, alias)
        -- If alias contains '_', accept '-' also.
        if alias:find("_", 1, true) then
            table.insert(self._aliases, (alias:gsub("_", "-")))
        end
    end

    -- Do not set _name as with other properties.
    return true
end}

local multiname_hidden = {"hidden_name", function(self, value)
    typecheck("hidden_name", {"string"}, value)

    for alias in value:gmatch("%S+") do
        table.insert(self._aliases, alias)
        if alias:find("_", 1, true) then
            table.insert(self._aliases, (alias:gsub("_", "-")))
        end
    end

    return true
end}

local function parse_boundaries(str)
    if tonumber(str) then
        return tonumber(str), tonumber(str)
    end

    if str == "*" then
        return 0, math.huge
    end

    if str == "+" then
        return 1, math.huge
    end

    if str == "?" then
        return 0, 1
    end

    if str:match "^%d+%-%d+$" then
        local min, max = str:match "^(%d+)%-(%d+)$"
        return tonumber(min), tonumber(max)
    end

    if str:match "^%d+%+$" then
        local min = str:match "^(%d+)%+$"
        return tonumber(min), math.huge
    end
end

local function boundaries(name)
    return {name, function(self, value)
        typecheck(name, {"number", "string"}, value)

        local min, max = parse_boundaries(value)

        if not min then
            error(("bad property '%s'"):format(name))
        end

        self["_min" .. name], self["_max" .. name] = min, max
    end}
end

local actions = {}

local option_action = {"action", function(_, value)
    typecheck("action", {"function", "string"}, value)

    if type(value) == "string" and not actions[value] then
        error(("unknown action '%s'"):format(value))
    end
end}

local option_init = {"init", function(self)
    self._has_init = true
end}

local option_default = {"default", function(self, value)
    if type(value) ~= "string" then
        self._init = value
        self._has_init = true
        return true
    end
end}

local add_help = {"add_help", function(self, value)
    typecheck("add_help", {"boolean", "string", "table"}, value)

    if self._help_option_idx then
        table.remove(self._options, self._help_option_idx)
        self._help_option_idx = nil
    end

    if value then
        local help = self:flag()
                         :description "Show this help message and exit."
                         :action(function()
            print(self:get_help())
            os.exit(0)
        end)

        if value ~= true then
            help = help(value)
        end

        if not help._name then
            help "-h" "--help"
        end

        self._help_option_idx = #self._options
    end
end}

local Parser = class({
    _arguments = {},
    _options = {},
    _commands = {},
    _mutexes = {},
    _groups = {},
    _require_command = true,
    _handle_options = true
}, {
    args = 3,
    typechecked("name", "string"),
    typechecked("description", "string"),
    typechecked("epilog", "string"),
    typechecked("usage", "string"),
    typechecked("help", "string"),
    typechecked("require_command", "boolean"),
    typechecked("handle_options", "boolean"),
    typechecked("action", "function"),
    typechecked("command_target", "string"),
    typechecked("help_vertical_space", "number"),
    typechecked("usage_margin", "number"),
    typechecked("usage_max_width", "number"),
    typechecked("help_usage_margin", "number"),
    typechecked("help_description_margin", "number"),
    typechecked("help_max_width", "number"),
    add_help
})

local Command = class({
    _aliases = {},
    _public_aliases = {}
}, {
    args = 3,
    multiname,
    typechecked("description", "string"),
    typechecked("epilog", "string"),
    multiname_hidden,
    typechecked("summary", "string"),
    typechecked("target", "string"),
    typechecked("usage", "string"),
    typechecked("help", "string"),
    typechecked("require_command", "boolean"),
    typechecked("handle_options", "boolean"),
    typechecked("action", "function"),
    typechecked("command_target", "string"),
    typechecked("help_vertical_space", "number"),
    typechecked("usage_margin", "number"),
    typechecked("usage_max_width", "number"),
    typechecked("help_usage_margin", "number"),
    typechecked("help_description_margin", "number"),
    typechecked("help_max_width", "number"),
    typechecked("hidden", "boolean"),
    add_help
}, Parser)

local Argument = class({
    _minargs = 1,
    _maxargs = 1,
    _mincount = 1,
    _maxcount = 1,
    _defmode = "unused",
    _show_default = true
}, {
    args = 5,
    typechecked("name", "string"),
    typechecked("description", "string"),
    option_default,
    typechecked("convert", "function", "table"),
    boundaries("args"),
    typechecked("target", "string"),
    typechecked("defmode", "string"),
    typechecked("show_default", "boolean"),
    typechecked("argname", "string", "table"),
    typechecked("choices", "table"),
    typechecked("hidden", "boolean"),
    option_action,
    option_init
})

local Option = class({
    _aliases = {},
    _public_aliases = {},
    _mincount = 0,
    _overwrite = true
}, {
    args = 6,
    multiname,
    typechecked("description", "string"),
    option_default,
    typechecked("convert", "function", "table"),
    boundaries("args"),
    boundaries("count"),
    multiname_hidden,
    typechecked("target", "string"),
    typechecked("defmode", "string"),
    typechecked("show_default", "boolean"),
    typechecked("overwrite", "boolean"),
    typechecked("argname", "string", "table"),
    typechecked("choices", "table"),
    typechecked("hidden", "boolean"),
    option_action,
    option_init
}, Argument)

function Parser:_inherit_property(name, default)
    local element = self

    while true do
        local value = element["_" .. name]

        if value ~= nil then
            return value
        end

        if not element._parent then
            return default
        end

        element = element._parent
    end
end

function Argument:_get_argument_list()
    local buf = {}
    local i = 1

    while i <= math.min(self._minargs, 3) do
        local argname = self:_get_argname(i)

        if self._default and self._defmode:find "a" then
            argname = "[" .. argname .. "]"
        end

        table.insert(buf, argname)
        i = i+1
    end

    while i <= math.min(self._maxargs, 3) do
        table.insert(buf, "[" .. self:_get_argname(i) .. "]")
        i = i+1

        if self._maxargs == math.huge then
            break
        end
    end

    if i < self._maxargs then
        table.insert(buf, "...")
    end

    return buf
end

function Argument:_get_usage()
    local usage = table.concat(self:_get_argument_list(), " ")

    if self._default and self._defmode:find "u" then
        if self._maxargs > 1 or (self._minargs == 1 and not self._defmode:find "a") then
            usage = "[" .. usage .. "]"
        end
    end

    return usage
end

function actions.store_true(result, target)
    result[target] = true
end

function actions.store_false(result, target)
    result[target] = false
end

function actions.store(result, target, argument)
    result[target] = argument
end

function actions.count(result, target, _, overwrite)
    if not overwrite then
        result[target] = result[target] + 1
    end
end

function actions.append(result, target, argument, overwrite)
    result[target] = result[target] or {}
    table.insert(result[target], argument)

    if overwrite then
        table.remove(result[target], 1)
    end
end

function actions.concat(result, target, arguments, overwrite)
    if overwrite then
        error("'concat' action can't handle too many invocations")
    end

    result[target] = result[target] or {}

    for _, argument in ipairs(arguments) do
        table.insert(result[target], argument)
    end
end

function Argument:_get_action()
    local action, init

    if self._maxcount == 1 then
        if self._maxargs == 0 then
            action, init = "store_true", nil
        else
            action, init = "store", nil
        end
    else
        if self._maxargs == 0 then
            action, init = "count", 0
        else
            action, init = "append", {}
        end
    end

    if self._action then
        action = self._action
    end

    if self._has_init then
        init = self._init
    end

    if type(action) == "string" then
        action = actions[action]
    end

    return action, init
end

-- Returns placeholder for `narg`-th argument.
function Argument:_get_argname(narg)
    local argname = self._argname or self:_get_default_argname()

    if type(argname) == "table" then
        return argname[narg]
    else
        return argname
    end
end

function Argument:_get_choices_list()
    return "{" .. table.concat(self._choices, ",") .. "}"
end

function Argument:_get_default_argname()
    if self._choices then
        return self:_get_choices_list()
    else
        return "<" .. self._name .. ">"
    end
end

function Option:_get_default_argname()
    if self._choices then
        return self:_get_choices_list()
    else
        return "<" .. self:_get_default_target() .. ">"
    end
end

-- Returns labels to be shown in the help message.
function Argument:_get_label_lines()
    if self._choices then
        return {self:_get_choices_list()}
    else
        return {self._name}
    end
end

function Option:_get_label_lines()
    local argument_list = self:_get_argument_list()

    if #argument_list == 0 then
        -- Don't put aliases for simple flags like `-h` on different lines.
        return {table.concat(self._public_aliases, ", ")}
    end

    local longest_alias_length = -1

    for _, alias in ipairs(self._public_aliases) do
        longest_alias_length = math.max(longest_alias_length, #alias)
    end

    local argument_list_repr = table.concat(argument_list, " ")
    local lines = {}

    for i, alias in ipairs(self._public_aliases) do
        local line = (" "):rep(longest_alias_length - #alias) .. alias .. " " .. argument_list_repr

        if i ~= #self._public_aliases then
            line = line .. ","
        end

        table.insert(lines, line)
    end

    return lines
end

function Command:_get_label_lines()
    return {table.concat(self._public_aliases, ", ")}
end

function Argument:_get_description()
    if self._default and self._show_default then
        if self._description then
            return ("%s (default: %s)"):format(self._description, self._default)
        else
            return ("default: %s"):format(self._default)
        end
    else
        return self._description or ""
    end
end

function Command:_get_description()
    return self._summary or self._description or ""
end

function Option:_get_usage()
    local usage = self:_get_argument_list()
    table.insert(usage, 1, self._name)
    usage = table.concat(usage, " ")

    if self._mincount == 0 or self._default then
        usage = "[" .. usage .. "]"
    end

    return usage
end

function Argument:_get_default_target()
    return self._name
end

function Option:_get_default_target()
    local res

    for _, alias in ipairs(self._public_aliases) do
        if alias:sub(1, 1) == alias:sub(2, 2) then
            res = alias:sub(3)
            break
        end
    end

    res = res or self._name:sub(2)
    return (res:gsub("-", "_"))
end

function Option:_is_vararg()
    return self._maxargs ~= self._minargs
end

function Parser:_get_fullname(exclude_root)
    local parent = self._parent
    if exclude_root and not parent then
        return ""
    end
    local buf = {self._name}

    while parent do
        if not exclude_root or parent._parent then
            table.insert(buf, 1, parent._name)
        end
        parent = parent._parent
    end

    return table.concat(buf, " ")
end

function Parser:_update_charset(charset)
    charset = charset or {}

    for _, command in ipairs(self._commands) do
        command:_update_charset(charset)
    end

    for _, option in ipairs(self._options) do
        for _, alias in ipairs(option._aliases) do
            charset[alias:sub(1, 1)] = true
        end
    end

    return charset
end

function Parser:argument(...)
    local argument = Argument(...)
    table.insert(self._arguments, argument)
    return argument
end

function Parser:option(...)
    local option = Option(...)
    table.insert(self._options, option)
    return option
end

function Parser:flag(...)
    return self:option():args(0)(...)
end

function Parser:command(...)
    local command = Command():add_help(true)(...)
    command._parent = self
    table.insert(self._commands, command)
    return command
end

function Parser:mutex(...)
    local elements = {...}

    for i, element in ipairs(elements) do
        local mt = getmetatable(element)
        assert(mt == Option or mt == Argument, ("bad argument #%d to 'mutex' (Option or Argument expected)"):format(i))
    end

    table.insert(self._mutexes, elements)
    return self
end

function Parser:group(name, ...)
    assert(type(name) == "string", ("bad argument #1 to 'group' (string expected, got %s)"):format(type(name)))

    local group = {name = name, ...}

    for i, element in ipairs(group) do
        local mt = getmetatable(element)
        assert(mt == Option or mt == Argument or mt == Command,
                ("bad argument #%d to 'group' (Option or Argument or Command expected)"):format(i + 1))
    end

    table.insert(self._groups, group)
    return self
end

local usage_welcome = "Usage: "

function Parser:get_usage()
    if self._usage then
        return self._usage
    end

    local usage_margin = self:_inherit_property("usage_margin", #usage_welcome)
    local max_usage_width = self:_inherit_property("usage_max_width", 70)
    local lines = {usage_welcome .. self:_get_fullname()}

    local function add(s)
        if #lines[#lines]+1+#s <= max_usage_width then
            lines[#lines] = lines[#lines] .. " " .. s
        else
            lines[#lines+1] = (" "):rep(usage_margin) .. s
        end
    end

    -- Normally options are before positional arguments in usage messages.
    -- However, vararg options should be after, because they can't be reliable used
    -- before a positional argument.
    -- Mutexes come into play, too, and are shown as soon as possible.
    -- Overall, output usages in the following order:
    -- 1. Mutexes that don't have positional arguments or vararg options.
    -- 2. Options that are not in any mutexes and are not vararg.
    -- 3. Positional arguments - on their own or as a part of a mutex.
    -- 4. Remaining mutexes.
    -- 5. Remaining options.

    local elements_in_mutexes = {}
    local added_elements = {}
    local added_mutexes = {}
    local argument_to_mutexes = {}

    local function add_mutex(mutex, main_argument)
        if added_mutexes[mutex] then
            return
        end

        added_mutexes[mutex] = true
        local buf = {}

        for _, element in ipairs(mutex) do
            if not element._hidden and not added_elements[element] then
                if getmetatable(element) == Option or element == main_argument then
                    table.insert(buf, element:_get_usage())
                    added_elements[element] = true
                end
            end
        end

        if #buf == 1 then
            add(buf[1])
        elseif #buf > 1 then
            add("(" .. table.concat(buf, " | ") .. ")")
        end
    end

    local function add_element(element)
        if not element._hidden and not added_elements[element] then
            add(element:_get_usage())
            added_elements[element] = true
        end
    end

    for _, mutex in ipairs(self._mutexes) do
        local is_vararg = false
        local has_argument = false

        for _, element in ipairs(mutex) do
            if getmetatable(element) == Option then
                if element:_is_vararg() then
                    is_vararg = true
                end
            else
                has_argument = true
                argument_to_mutexes[element] = argument_to_mutexes[element] or {}
                table.insert(argument_to_mutexes[element], mutex)
            end

            elements_in_mutexes[element] = true
        end

        if not is_vararg and not has_argument then
            add_mutex(mutex)
        end
    end

    for _, option in ipairs(self._options) do
        if not elements_in_mutexes[option] and not option:_is_vararg() then
            add_element(option)
        end
    end

    -- Add usages for positional arguments, together with one mutex containing them, if they are in a mutex.
    for _, argument in ipairs(self._arguments) do
        -- Pick a mutex as a part of which to show this argument, take the first one that's still available.
        local mutex

        if elements_in_mutexes[argument] then
            for _, argument_mutex in ipairs(argument_to_mutexes[argument]) do
                if not added_mutexes[argument_mutex] then
                    mutex = argument_mutex
                end
            end
        end

        if mutex then
            add_mutex(mutex, argument)
        else
            add_element(argument)
        end
    end

    for _, mutex in ipairs(self._mutexes) do
        add_mutex(mutex)
    end

    for _, option in ipairs(self._options) do
        add_element(option)
    end

    if #self._commands > 0 then
        if self._require_command then
            add("<command>")
        else
            add("[<command>]")
        end

        add("...")
    end

    return table.concat(lines, "\n")
end

local function split_lines(s)
    if s == "" then
        return {}
    end

    local lines = {}

    if s:sub(-1) ~= "\n" then
        s = s .. "\n"
    end

    for line in s:gmatch("([^\n]*)\n") do
        table.insert(lines, line)
    end

    return lines
end

local function autowrap_line(line, max_length)
    -- Algorithm for splitting lines is simple and greedy.
    local result_lines = {}

    -- Preserve original indentation of the line, put this at the beginning of each result line.
    -- If the first word looks like a list marker ('*', '+', or '-'), add spaces so that starts
    -- of the second and the following lines vertically align with the start of the second word.
    local indentation = line:match("^ *")

    if line:find("^ *[%*%+%-]") then
        indentation = indentation .. " " .. line:match("^ *[%*%+%-]( *)")
    end

    -- Parts of the last line being assembled.
    local line_parts = {}

    -- Length of the current line.
    local line_length = 0

    -- Index of the next character to consider.
    local index = 1

    while true do
        local word_start, word_finish, word = line:find("([^ ]+)", index)

        if not word_start then
            -- Ignore trailing spaces, if any.
            break
        end

        local preceding_spaces = line:sub(index, word_start - 1)
        index = word_finish + 1

        if (#line_parts == 0) or (line_length + #preceding_spaces + #word <= max_length) then
            -- Either this is the very first word or it fits as an addition to the current line, add it.
            table.insert(line_parts, preceding_spaces) -- For the very first word this adds the indentation.
            table.insert(line_parts, word)
            line_length = line_length + #preceding_spaces + #word
        else
            -- Does not fit, finish current line and put the word into a new one.
            table.insert(result_lines, table.concat(line_parts))
            line_parts = {indentation, word}
            line_length = #indentation + #word
        end
    end

    if #line_parts > 0 then
        table.insert(result_lines, table.concat(line_parts))
    end

    if #result_lines == 0 then
        -- Preserve empty lines.
        result_lines[1] = ""
    end

    return result_lines
end

-- Automatically wraps lines within given array,
-- attempting to limit line length to `max_length`.
-- Existing line splits are preserved.
local function autowrap(lines, max_length)
    local result_lines = {}

    for _, line in ipairs(lines) do
        local autowrapped_lines = autowrap_line(line, max_length)

        for _, autowrapped_line in ipairs(autowrapped_lines) do
            table.insert(result_lines, autowrapped_line)
        end
    end

    return result_lines
end

function Parser:_get_element_help(element)
    local label_lines = element:_get_label_lines()
    local description_lines = split_lines(element:_get_description())

    local result_lines = {}

    -- All label lines should have the same length (except the last one, it has no comma).
    -- If too long, start description after all the label lines.
    -- Otherwise, combine label and description lines.

    local usage_margin_len = self:_inherit_property("help_usage_margin", 3)
    local usage_margin = (" "):rep(usage_margin_len)
    local description_margin_len = self:_inherit_property("help_description_margin", 25)
    local description_margin = (" "):rep(description_margin_len)

    local help_max_width = self:_inherit_property("help_max_width")

    if help_max_width then
        local description_max_width = math.max(help_max_width - description_margin_len, 10)
        description_lines = autowrap(description_lines, description_max_width)
    end

    if #label_lines[1] >= (description_margin_len - usage_margin_len) then
        for _, label_line in ipairs(label_lines) do
            table.insert(result_lines, usage_margin .. label_line)
        end

        for _, description_line in ipairs(description_lines) do
            table.insert(result_lines, description_margin .. description_line)
        end
    else
        for i = 1, math.max(#label_lines, #description_lines) do
            local label_line = label_lines[i]
            local description_line = description_lines[i]

            local line = ""

            if label_line then
                line = usage_margin .. label_line
            end

            if description_line and description_line ~= "" then
                line = line .. (" "):rep(description_margin_len - #line) .. description_line
            end

            table.insert(result_lines, line)
        end
    end

    return table.concat(result_lines, "\n")
end

local function get_group_types(group)
    local types = {}

    for _, element in ipairs(group) do
        types[getmetatable(element)] = true
    end

    return types
end

function Parser:_add_group_help(blocks, added_elements, label, elements)
    local buf = {label}

    for _, element in ipairs(elements) do
        if not element._hidden and not added_elements[element] then
            added_elements[element] = true
            table.insert(buf, self:_get_element_help(element))
        end
    end

    if #buf > 1 then
        table.insert(blocks, table.concat(buf, ("\n"):rep(self:_inherit_property("help_vertical_space", 0) + 1)))
    end
end

function Parser:get_help()
    if self._help then
        return self._help
    end

    local blocks = {self:get_usage()}

    local help_max_width = self:_inherit_property("help_max_width")

    if self._description then
        local description = self._description

        if help_max_width then
            description = table.concat(autowrap(split_lines(description), help_max_width), "\n")
        end

        table.insert(blocks, description)
    end

    -- 1. Put groups containing arguments first, then other arguments.
    -- 2. Put remaining groups containing options, then other options.
    -- 3. Put remaining groups containing commands, then other commands.
    -- Assume that an element can't be in several groups.
    local groups_by_type = {
        [Argument] = {},
        [Option] = {},
        [Command] = {}
    }

    for _, group in ipairs(self._groups) do
        local group_types = get_group_types(group)

        for _, mt in ipairs({Argument, Option, Command}) do
            if group_types[mt] then
                table.insert(groups_by_type[mt], group)
                break
            end
        end
    end

    local default_groups = {
        {name = "Arguments", type = Argument, elements = self._arguments},
        {name = "Options", type = Option, elements = self._options},
        {name = "Commands", type = Command, elements = self._commands}
    }

    local added_elements = {}

    for _, default_group in ipairs(default_groups) do
        local type_groups = groups_by_type[default_group.type]

        for _, group in ipairs(type_groups) do
            self:_add_group_help(blocks, added_elements, group.name .. ":", group)
        end

        local default_label = default_group.name .. ":"

        if #type_groups > 0 then
            default_label = "Other " .. default_label:gsub("^.", string.lower)
        end

        self:_add_group_help(blocks, added_elements, default_label, default_group.elements)
    end

    if self._epilog then
        local epilog = self._epilog

        if help_max_width then
            epilog = table.concat(autowrap(split_lines(epilog), help_max_width), "\n")
        end

        table.insert(blocks, epilog)
    end

    return table.concat(blocks, "\n\n")
end

function Parser:add_help_command(value)
    if value then
        assert(type(value) == "string" or type(value) == "table",
                ("bad argument #1 to 'add_help_command' (string or table expected, got %s)"):format(type(value)))
    end

    local help = self:command()
                     :description "Show help for commands."
    help:argument "command"
        :description "The command to show help for."
        :args "?"
        :action(function(_, _, cmd)
        if not cmd then
            print(self:get_help())
            os.exit(0)
        else
            for _, command in ipairs(self._commands) do
                for _, alias in ipairs(command._aliases) do
                    if alias == cmd then
                        print(command:get_help())
                        os.exit(0)
                    end
                end
            end
        end
        help:error(("unknown command '%s'"):format(cmd))
    end)

    if value then
        help = help(value)
    end

    if not help._name then
        help "help"
    end

    help._is_help_command = true
    return self
end

function Parser:_is_shell_safe()
    if self._basename then
        if self._basename:find("[^%w_%-%+%.]") then
            return false
        end
    else
        for _, alias in ipairs(self._aliases) do
            if alias:find("[^%w_%-%+%.]") then
                return false
            end
        end
    end
    for _, option in ipairs(self._options) do
        for _, alias in ipairs(option._aliases) do
            if alias:find("[^%w_%-%+%.]") then
                return false
            end
        end
        if option._choices then
            for _, choice in ipairs(option._choices) do
                if choice:find("[%s'\"]") then
                    return false
                end
            end
        end
    end
    for _, argument in ipairs(self._arguments) do
        if argument._choices then
            for _, choice in ipairs(argument._choices) do
                if choice:find("[%s'\"]") then
                    return false
                end
            end
        end
    end
    for _, command in ipairs(self._commands) do
        if not command:_is_shell_safe() then
            return false
        end
    end
    return true
end

function Parser:add_complete(value)
    if value then
        assert(type(value) == "string" or type(value) == "table",
                ("bad argument #1 to 'add_complete' (string or table expected, got %s)"):format(type(value)))
    end

    local complete = self:option()
                         :description "Output a shell completion script for the specified shell."
                         :args(1)
                         :choices {"bash", "zsh", "fish"}
                         :action(function(_, _, shell)
        io.write(self["get_" .. shell .. "_complete"](self))
        os.exit(0)
    end)

    if value then
        complete = complete(value)
    end

    if not complete._name then
        complete "--completion"
    end

    return self
end

function Parser:add_complete_command(value)
    if value then
        assert(type(value) == "string" or type(value) == "table",
                ("bad argument #1 to 'add_complete_command' (string or table expected, got %s)"):format(type(value)))
    end

    local complete = self:command()
                         :description "Output a shell completion script."
    complete:argument "shell"
            :description "The shell to output a completion script for."
            :choices {"bash", "zsh", "fish"}
            :action(function(_, _, shell)
        io.write(self["get_" .. shell .. "_complete"](self))
        os.exit(0)
    end)

    if value then
        complete = complete(value)
    end

    if not complete._name then
        complete "completion"
    end

    return self
end

local function base_name(pathname)
    return pathname:gsub("[/\\]*$", ""):match(".*[/\\]([^/\\]*)") or pathname
end

local function get_short_description(element)
    local short = element:_get_description():match("^(.-)%.%s")
    return short or element:_get_description():match("^(.-)%.?$")
end

function Parser:_get_options()
    local options = {}
    for _, option in ipairs(self._options) do
        for _, alias in ipairs(option._aliases) do
            table.insert(options, alias)
        end
    end
    return table.concat(options, " ")
end

function Parser:_get_commands()
    local commands = {}
    for _, command in ipairs(self._commands) do
        for _, alias in ipairs(command._aliases) do
            table.insert(commands, alias)
        end
    end
    return table.concat(commands, " ")
end

function Parser:_bash_option_args(buf, indent)
    local opts = {}
    for _, option in ipairs(self._options) do
        if option._choices or option._minargs > 0 then
            local compreply
            if option._choices then
                compreply = 'COMPREPLY=($(compgen -W "' .. table.concat(option._choices, " ") .. '" -- "$cur"))'
            else
                compreply = 'COMPREPLY=($(compgen -f -- "$cur"))'
            end
            table.insert(opts, (" "):rep(indent + 4) .. table.concat(option._aliases, "|") .. ")")
            table.insert(opts, (" "):rep(indent + 8) .. compreply)
            table.insert(opts, (" "):rep(indent + 8) .. "return 0")
            table.insert(opts, (" "):rep(indent + 8) .. ";;")
        end
    end

    if #opts > 0 then
        table.insert(buf, (" "):rep(indent) .. 'case "$prev" in')
        table.insert(buf, table.concat(opts, "\n"))
        table.insert(buf, (" "):rep(indent) .. "esac\n")
    end
end

function Parser:_bash_get_cmd(buf, indent)
    if #self._commands == 0 then
        return
    end

    table.insert(buf, (" "):rep(indent) .. 'args=("${args[@]:1}")')
    table.insert(buf, (" "):rep(indent) .. 'for arg in "${args[@]}"; do')
    table.insert(buf, (" "):rep(indent + 4) .. 'case "$arg" in')

    for _, command in ipairs(self._commands) do
        table.insert(buf, (" "):rep(indent + 8) .. table.concat(command._aliases, "|") .. ")")
        if self._parent then
            table.insert(buf, (" "):rep(indent + 12) .. 'cmd="$cmd ' .. command._name .. '"')
        else
            table.insert(buf, (" "):rep(indent + 12) .. 'cmd="' .. command._name .. '"')
        end
        table.insert(buf, (" "):rep(indent + 12) .. 'opts="$opts ' .. command:_get_options() .. '"')
        command:_bash_get_cmd(buf, indent + 12)
        table.insert(buf, (" "):rep(indent + 12) .. "break")
        table.insert(buf, (" "):rep(indent + 12) .. ";;")
    end

    table.insert(buf, (" "):rep(indent + 4) .. "esac")
    table.insert(buf, (" "):rep(indent) .. "done")
end

function Parser:_bash_cmd_completions(buf)
    local cmd_buf = {}
    if self._parent then
        self:_bash_option_args(cmd_buf, 12)
    end
    if #self._commands > 0 then
        table.insert(cmd_buf, (" "):rep(12) .. 'COMPREPLY=($(compgen -W "' .. self:_get_commands() .. '" -- "$cur"))')
    elseif self._is_help_command then
        table.insert(cmd_buf, (" "):rep(12)
                .. 'COMPREPLY=($(compgen -W "'
                .. self._parent:_get_commands()
                .. '" -- "$cur"))')
    end
    if #cmd_buf > 0 then
        table.insert(buf, (" "):rep(8) .. "'" .. self:_get_fullname(true) .. "')")
        table.insert(buf, table.concat(cmd_buf, "\n"))
        table.insert(buf, (" "):rep(12) .. ";;")
    end

    for _, command in ipairs(self._commands) do
        command:_bash_cmd_completions(buf)
    end
end

function Parser:get_bash_complete()
    self._basename = base_name(self._name)
    assert(self:_is_shell_safe())
    local buf = {([[
_%s() {
    local IFS=$' \t\n'
    local args cur prev cmd opts arg
    args=("${COMP_WORDS[@]}")
    cur="${COMP_WORDS[COMP_CWORD]}"
    prev="${COMP_WORDS[COMP_CWORD-1]}"
    opts="%s"
]]):format(self._basename, self:_get_options())}

    self:_bash_option_args(buf, 4)
    self:_bash_get_cmd(buf, 4)
    if #self._commands > 0 then
        table.insert(buf, "")
        table.insert(buf, (" "):rep(4) .. 'case "$cmd" in')
        self:_bash_cmd_completions(buf)
        table.insert(buf, (" "):rep(4) .. "esac\n")
    end

    table.insert(buf, ([=[
    if [[ "$cur" = -* ]]; then
        COMPREPLY=($(compgen -W "$opts" -- "$cur"))
    fi
}

complete -F _%s -o bashdefault -o default %s
]=]):format(self._basename, self._basename))

    return table.concat(buf, "\n")
end

function Parser:_zsh_arguments(buf, cmd_name, indent)
    if self._parent then
        table.insert(buf, (" "):rep(indent) .. "options=(")
        table.insert(buf, (" "):rep(indent + 2) .. "$options")
    else
        table.insert(buf, (" "):rep(indent) .. "local -a options=(")
    end

    for _, option in ipairs(self._options) do
        local line = {}
        if #option._aliases > 1 then
            if option._maxcount > 1 then
                table.insert(line, '"*"')
            end
            table.insert(line, "{" .. table.concat(option._aliases, ",") .. '}"')
        else
            table.insert(line, '"')
            if option._maxcount > 1 then
                table.insert(line, "*")
            end
            table.insert(line, option._name)
        end
        if option._description then
            local description = get_short_description(option):gsub('["%]:`$]', "\\%0")
            table.insert(line, "[" .. description .. "]")
        end
        if option._maxargs == math.huge then
            table.insert(line, ":*")
        end
        if option._choices then
            table.insert(line, ": :(" .. table.concat(option._choices, " ") .. ")")
        elseif option._maxargs > 0 then
            table.insert(line, ": :_files")
        end
        table.insert(line, '"')
        table.insert(buf, (" "):rep(indent + 2) .. table.concat(line))
    end

    table.insert(buf, (" "):rep(indent) .. ")")
    table.insert(buf, (" "):rep(indent) .. "_arguments -s -S \\")
    table.insert(buf, (" "):rep(indent + 2) .. "$options \\")

    if self._is_help_command then
        table.insert(buf, (" "):rep(indent + 2) .. '": :(' .. self._parent:_get_commands() .. ')" \\')
    else
        for _, argument in ipairs(self._arguments) do
            local spec
            if argument._choices then
                spec = ": :(" .. table.concat(argument._choices, " ") .. ")"
            else
                spec = ": :_files"
            end
            if argument._maxargs == math.huge then
                table.insert(buf, (" "):rep(indent + 2) .. '"*' .. spec .. '" \\')
                break
            end
            for _ = 1, argument._maxargs do
                table.insert(buf, (" "):rep(indent + 2) .. '"' .. spec .. '" \\')
            end
        end

        if #self._commands > 0 then
            table.insert(buf, (" "):rep(indent + 2) .. '": :_' .. cmd_name .. '_cmds" \\')
            table.insert(buf, (" "):rep(indent + 2) .. '"*:: :->args" \\')
        end
    end

    table.insert(buf, (" "):rep(indent + 2) .. "&& return 0")
end

function Parser:_zsh_cmds(buf, cmd_name)
    table.insert(buf, "\n_" .. cmd_name .. "_cmds() {")
    table.insert(buf, "  local -a commands=(")

    for _, command in ipairs(self._commands) do
        local line = {}
        if #command._aliases > 1 then
            table.insert(line, "{" .. table.concat(command._aliases, ",") .. '}"')
        else
            table.insert(line, '"' .. command._name)
        end
        if command._description then
            table.insert(line, ":" .. get_short_description(command):gsub('["`$]', "\\%0"))
        end
        table.insert(buf, "    " .. table.concat(line) .. '"')
    end

    table.insert(buf, '  )\n  _describe "command" commands\n}')
end

function Parser:_zsh_complete_help(buf, cmds_buf, cmd_name, indent)
    if #self._commands == 0 then
        return
    end

    self:_zsh_cmds(cmds_buf, cmd_name)
    table.insert(buf, "\n" .. (" "):rep(indent) .. "case $words[1] in")

    for _, command in ipairs(self._commands) do
        local name = cmd_name .. "_" .. command._name
        table.insert(buf, (" "):rep(indent + 2) .. table.concat(command._aliases, "|") .. ")")
        command:_zsh_arguments(buf, name, indent + 4)
        command:_zsh_complete_help(buf, cmds_buf, name, indent + 4)
        table.insert(buf, (" "):rep(indent + 4) .. ";;\n")
    end

    table.insert(buf, (" "):rep(indent) .. "esac")
end

function Parser:get_zsh_complete()
    self._basename = base_name(self._name)
    assert(self:_is_shell_safe())
    local buf = {("#compdef %s\n"):format(self._basename)}
    local cmds_buf = {}
    table.insert(buf, "_" .. self._basename .. "() {")
    if #self._commands > 0 then
        table.insert(buf, "  local context state state_descr line")
        table.insert(buf, "  typeset -A opt_args\n")
    end
    self:_zsh_arguments(buf, self._basename, 2)
    self:_zsh_complete_help(buf, cmds_buf, self._basename, 2)
    table.insert(buf, "\n  return 1")
    table.insert(buf, "}")

    local result = table.concat(buf, "\n")
    if #cmds_buf > 0 then
        result = result .. "\n" .. table.concat(cmds_buf, "\n")
    end
    return result .. "\n\n_" .. self._basename .. "\n"
end

local function fish_escape(string)
    return string:gsub("[\\']", "\\%0")
end

function Parser:_fish_get_cmd(buf, indent)
    if #self._commands == 0 then
        return
    end

    table.insert(buf, (" "):rep(indent) .. "set -e cmdline[1]")
    table.insert(buf, (" "):rep(indent) .. "for arg in $cmdline")
    table.insert(buf, (" "):rep(indent + 4) .. "switch $arg")

    for _, command in ipairs(self._commands) do
        table.insert(buf, (" "):rep(indent + 8) .. "case " .. table.concat(command._aliases, " "))
        table.insert(buf, (" "):rep(indent + 12) .. "set cmd $cmd " .. command._name)
        command:_fish_get_cmd(buf, indent + 12)
        table.insert(buf, (" "):rep(indent + 12) .. "break")
    end

    table.insert(buf, (" "):rep(indent + 4) .. "end")
    table.insert(buf, (" "):rep(indent) .. "end")
end

function Parser:_fish_complete_help(buf, basename)
    local prefix = "complete -c " .. basename
    table.insert(buf, "")

    for _, command in ipairs(self._commands) do
        local aliases = table.concat(command._aliases, " ")
        local line
        if self._parent then
            line = ("%s -n '__fish_%s_using_command %s' -xa '%s'")
                    :format(prefix, basename, self:_get_fullname(true), aliases)
        else
            line = ("%s -n '__fish_%s_using_command' -xa '%s'"):format(prefix, basename, aliases)
        end
        if command._description then
            line = ("%s -d '%s'"):format(line, fish_escape(get_short_description(command)))
        end
        table.insert(buf, line)
    end

    if self._is_help_command then
        local line = ("%s -n '__fish_%s_using_command %s' -xa '%s'")
                :format(prefix, basename, self:_get_fullname(true), self._parent:_get_commands())
        table.insert(buf, line)
    end

    for _, option in ipairs(self._options) do
        local parts = {prefix}

        if self._parent then
            table.insert(parts, "-n '__fish_" .. basename .. "_seen_command " .. self:_get_fullname(true) .. "'")
        end

        for _, alias in ipairs(option._aliases) do
            if alias:match("^%-.$") then
                table.insert(parts, "-s " .. alias:sub(2))
            elseif alias:match("^%-%-.+") then
                table.insert(parts, "-l " .. alias:sub(3))
            end
        end

        if option._choices then
            table.insert(parts, "-xa '" .. table.concat(option._choices, " ") .. "'")
        elseif option._minargs > 0 then
            table.insert(parts, "-r")
        end

        if option._description then
            table.insert(parts, "-d '" .. fish_escape(get_short_description(option)) .. "'")
        end

        table.insert(buf, table.concat(parts, " "))
    end

    for _, command in ipairs(self._commands) do
        command:_fish_complete_help(buf, basename)
    end
end

function Parser:get_fish_complete()
    self._basename = base_name(self._name)
    assert(self:_is_shell_safe())
    local buf = {}

    if #self._commands > 0 then
        table.insert(buf, ([[
function __fish_%s_print_command
    set -l cmdline (commandline -poc)
    set -l cmd]]):format(self._basename))
        self:_fish_get_cmd(buf, 4)
        table.insert(buf, ([[
    echo "$cmd"
end

function __fish_%s_using_command
    test (__fish_%s_print_command) = "$argv"
    and return 0
    or return 1
end

function __fish_%s_seen_command
    string match -q "$argv*" (__fish_%s_print_command)
    and return 0
    or return 1
end]]):format(self._basename, self._basename, self._basename, self._basename))
    end

    self:_fish_complete_help(buf, self._basename)
    return table.concat(buf, "\n") .. "\n"
end

local function get_tip(context, wrong_name)
    local context_pool = {}
    local possible_name
    local possible_names = {}

    for name in pairs(context) do
        if type(name) == "string" then
            for i = 1, #name do
                possible_name = name:sub(1, i - 1) .. name:sub(i + 1)

                if not context_pool[possible_name] then
                    context_pool[possible_name] = {}
                end

                table.insert(context_pool[possible_name], name)
            end
        end
    end

    for i = 1, #wrong_name + 1 do
        possible_name = wrong_name:sub(1, i - 1) .. wrong_name:sub(i + 1)

        if context[possible_name] then
            possible_names[possible_name] = true
        elseif context_pool[possible_name] then
            for _, name in ipairs(context_pool[possible_name]) do
                possible_names[name] = true
            end
        end
    end

    local first = next(possible_names)

    if first then
        if next(possible_names, first) then
            local possible_names_arr = {}

            for name in pairs(possible_names) do
                table.insert(possible_names_arr, "'" .. name .. "'")
            end

            table.sort(possible_names_arr)
            return "\nDid you mean one of these: " .. table.concat(possible_names_arr, " ") .. "?"
        else
            return "\nDid you mean '" .. first .. "'?"
        end
    else
        return ""
    end
end

local ElementState = class({
    invocations = 0
})

function ElementState:__call(state, element)
    self.state = state
    self.result = state.result
    self.element = element
    self.target = element._target or element:_get_default_target()
    self.action, self.result[self.target] = element:_get_action()
    return self
end

function ElementState:error(fmt, ...)
    self.state:error(fmt, ...)
end

function ElementState:convert(argument, index)
    local converter = self.element._convert

    if converter then
        local ok, err

        if type(converter) == "function" then
            ok, err = converter(argument)
        elseif type(converter[index]) == "function" then
            ok, err = converter[index](argument)
        else
            ok = converter[argument]
        end

        if ok == nil then
            self:error(err and "%s" or "malformed argument '%s'", err or argument)
        end

        argument = ok
    end

    return argument
end

function ElementState:default(mode)
    return self.element._defmode:find(mode) and self.element._default
end

local function bound(noun, min, max, is_max)
    local res = ""

    if min ~= max then
        res = "at " .. (is_max and "most" or "least") .. " "
    end

    local number = is_max and max or min
    return res .. tostring(number) .. " " .. noun ..  (number == 1 and "" or "s")
end

function ElementState:set_name(alias)
    self.name = ("%s '%s'"):format(alias and "option" or "argument", alias or self.element._name)
end

function ElementState:invoke()
    self.open = true
    self.overwrite = false

    if self.invocations >= self.element._maxcount then
        if self.element._overwrite then
            self.overwrite = true
        else
            local num_times_repr = bound("time", self.element._mincount, self.element._maxcount, true)
            self:error("%s must be used %s", self.name, num_times_repr)
        end
    else
        self.invocations = self.invocations + 1
    end

    self.args = {}

    if self.element._maxargs <= 0 then
        self:close()
    end

    return self.open
end

function ElementState:check_choices(argument)
    if self.element._choices then
        for _, choice in ipairs(self.element._choices) do
            if argument == choice then
                return
            end
        end
        local choices_list = "'" .. table.concat(self.element._choices, "', '") .. "'"
        local is_option = getmetatable(self.element) == Option
        self:error("%s%s must be one of %s", is_option and "argument for " or "", self.name, choices_list)
    end
end

function ElementState:pass(argument)
    self:check_choices(argument)
    argument = self:convert(argument, #self.args + 1)
    table.insert(self.args, argument)

    if #self.args >= self.element._maxargs then
        self:close()
    end

    return self.open
end

function ElementState:complete_invocation()
    while #self.args < self.element._minargs do
        self:pass(self.element._default)
    end
end

function ElementState:close()
    if self.open then
        self.open = false

        if #self.args < self.element._minargs then
            if self:default("a") then
                self:complete_invocation()
            else
                if #self.args == 0 then
                    if getmetatable(self.element) == Argument then
                        self:error("missing %s", self.name)
                    elseif self.element._maxargs == 1 then
                        self:error("%s requires an argument", self.name)
                    end
                end

                self:error("%s requires %s", self.name, bound("argument", self.element._minargs, self.element._maxargs))
            end
        end

        local args

        if self.element._maxargs == 0 then
            args = self.args[1]
        elseif self.element._maxargs == 1 then
            if self.element._minargs == 0 and self.element._mincount ~= self.element._maxcount then
                args = self.args
            else
                args = self.args[1]
            end
        else
            args = self.args
        end

        self.action(self.result, self.target, args, self.overwrite)
    end
end

local ParseState = class({
    result = {},
    options = {},
    arguments = {},
    argument_i = 1,
    element_to_mutexes = {},
    mutex_to_element_state = {},
    command_actions = {}
})

function ParseState:__call(parser, error_handler)
    self.parser = parser
    self.error_handler = error_handler
    self.charset = parser:_update_charset()
    self:switch(parser)
    return self
end

function ParseState:error(fmt, ...)
    self.error_handler(self.parser, fmt:format(...))
end

function ParseState:switch(parser)
    self.parser = parser

    if parser._action then
        table.insert(self.command_actions, {action = parser._action, name = parser._name})
    end

    for _, option in ipairs(parser._options) do
        option = ElementState(self, option)
        table.insert(self.options, option)

        for _, alias in ipairs(option.element._aliases) do
            self.options[alias] = option
        end
    end

    for _, mutex in ipairs(parser._mutexes) do
        for _, element in ipairs(mutex) do
            if not self.element_to_mutexes[element] then
                self.element_to_mutexes[element] = {}
            end

            table.insert(self.element_to_mutexes[element], mutex)
        end
    end

    for _, argument in ipairs(parser._arguments) do
        argument = ElementState(self, argument)
        table.insert(self.arguments, argument)
        argument:set_name()
        argument:invoke()
    end

    self.handle_options = parser._handle_options
    self.argument = self.arguments[self.argument_i]
    self.commands = parser._commands

    for _, command in ipairs(self.commands) do
        for _, alias in ipairs(command._aliases) do
            self.commands[alias] = command
        end
    end
end

function ParseState:get_option(name)
    local option = self.options[name]

    if not option then
        self:error("unknown option '%s'%s", name, get_tip(self.options, name))
    else
        return option
    end
end

function ParseState:get_command(name)
    local command = self.commands[name]

    if not command then
        if #self.commands > 0 then
            self:error("unknown command '%s'%s", name, get_tip(self.commands, name))
        else
            self:error("too many arguments")
        end
    else
        return command
    end
end

function ParseState:check_mutexes(element_state)
    if self.element_to_mutexes[element_state.element] then
        for _, mutex in ipairs(self.element_to_mutexes[element_state.element]) do
            local used_element_state = self.mutex_to_element_state[mutex]

            if used_element_state and used_element_state ~= element_state then
                self:error("%s can not be used together with %s", element_state.name, used_element_state.name)
            else
                self.mutex_to_element_state[mutex] = element_state
            end
        end
    end
end

function ParseState:invoke(option, name)
    self:close()
    option:set_name(name)
    self:check_mutexes(option, name)

    if option:invoke() then
        self.option = option
    end
end

function ParseState:pass(arg)
    if self.option then
        if not self.option:pass(arg) then
            self.option = nil
        end
    elseif self.argument then
        self:check_mutexes(self.argument)

        if not self.argument:pass(arg) then
            self.argument_i = self.argument_i + 1
            self.argument = self.arguments[self.argument_i]
        end
    else
        local command = self:get_command(arg)
        self.result[command._target or command._name] = true

        if self.parser._command_target then
            self.result[self.parser._command_target] = command._name
        end

        self:switch(command)
    end
end

function ParseState:close()
    if self.option then
        self.option:close()
        self.option = nil
    end
end

function ParseState:finalize()
    self:close()

    for i = self.argument_i, #self.arguments do
        local argument = self.arguments[i]
        if #argument.args == 0 and argument:default("u") then
            argument:complete_invocation()
        else
            argument:close()
        end
    end

    if self.parser._require_command and #self.commands > 0 then
        self:error("a command is required")
    end

    for _, option in ipairs(self.options) do
        option.name = option.name or ("option '%s'"):format(option.element._name)

        if option.invocations == 0 then
            if option:default("u") then
                option:invoke()
                option:complete_invocation()
                option:close()
            end
        end

        local mincount = option.element._mincount

        if option.invocations < mincount then
            if option:default("a") then
                while option.invocations < mincount do
                    option:invoke()
                    option:close()
                end
            elseif option.invocations == 0 then
                self:error("missing %s", option.name)
            else
                self:error("%s must be used %s", option.name, bound("time", mincount, option.element._maxcount))
            end
        end
    end

    for i = #self.command_actions, 1, -1 do
        self.command_actions[i].action(self.result, self.command_actions[i].name)
    end
end

function ParseState:parse(args)
    for _, arg in ipairs(args) do
        local plain = true

        if self.handle_options then
            local first = arg:sub(1, 1)

            if self.charset[first] then
                if #arg > 1 then
                    plain = false

                    if arg:sub(2, 2) == first then
                        if #arg == 2 then
                            if self.options[arg] then
                                local option = self:get_option(arg)
                                self:invoke(option, arg)
                            else
                                self:close()
                            end

                            self.handle_options = false
                        else
                            local equals = arg:find "="
                            if equals then
                                local name = arg:sub(1, equals - 1)
                                local option = self:get_option(name)

                                if option.element._maxargs <= 0 then
                                    self:error("option '%s' does not take arguments", name)
                                end

                                self:invoke(option, name)
                                self:pass(arg:sub(equals + 1))
                            else
                                local option = self:get_option(arg)
                                self:invoke(option, arg)
                            end
                        end
                    else
                        for i = 2, #arg do
                            local name = first .. arg:sub(i, i)
                            local option = self:get_option(name)
                            self:invoke(option, name)

                            if i ~= #arg and option.element._maxargs > 0 then
                                self:pass(arg:sub(i + 1))
                                break
                            end
                        end
                    end
                end
            end
        end

        if plain then
            self:pass(arg)
        end
    end

    self:finalize()
    return self.result
end

function Parser:error(msg)
    io.stderr:write(("%s\n\nError: %s\n"):format(self:get_usage(), msg))
    os.exit(1)
end

-- Compatibility with strict.lua and other checkers:
local default_cmdline = rawget(_G, "arg") or {}

function Parser:_parse(args, error_handler)
    return ParseState(self, error_handler):parse(args or default_cmdline)
end

function Parser:parse(args)
    return self:_parse(args, self.error)
end

local function xpcall_error_handler(err)
    return tostring(err) .. "\noriginal " .. debug.traceback("", 2):sub(2)
end

function Parser:pparse(args)
    local parse_error

    local ok, result = xpcall(function()
        return self:_parse(args, function(_, err)
            parse_error = err
            error(err, 0)
        end)
    end, xpcall_error_handler)

    if ok then
        return true, result
    elseif not parse_error then
        error(result, 0)
    else
        return false, parse_error
    end
end

local argparse = {}

argparse.version = "0.7.1"

setmetatable(argparse, {__call = function(_, ...)
    return Parser(default_cmdline[0]):add_help(true)(...)
end})

return argparse