## lib/trollop.rb -- trollop command-line processing library
## Author::    William Morgan (mailto: wmorgan-trollop@masanjin.net)
## Copyright:: Copyright 2007 William Morgan
## License::   the same terms as ruby itself

require 'date'

module Trollop

# Version of the Trollop library.
VERSION = "2.0"

# Thrown by Parser in the event of a commandline error. Not needed if
# you're using the `Trollop::options` entry.
class CommandlineError < StandardError; end

# Thrown by Parser if the user passes in `-h` or `--help`. Handled
# automatically by `Trollop#options`.
class HelpNeeded < StandardError; end

# Thrown by Parser if the user passes in `-h` or `--version`. Handled
# automatically by `Trollop#options`.
class VersionNeeded < StandardError; end

# Regex for floating point numbers
FLOAT_RE = /^-?((\d+(\.\d+)?)|(\.\d+))([eE][-+]?[\d]+)?$/

# Regex for parameters
PARAM_RE = /^-(-|\.$|[^\d\.])/

# The commandline parser. In typical usage, the methods in this class
# will be handled internally by `Trollop::options`. In this case, only the
# `#opt`, `#banner` and `#version`, `#depends`, and `#conflicts` methods will
# typically be called.
#
# If you want to instantiate this class yourself (for more complicated
# argument-parsing logic), call `#parse` to actually produce the output hash,
# and consider calling it from within `Trollop::with_standard_exception_handling`.
class Parser

  # The set of values that indicate a flag option when passed as the
  # `:type` parameter of #opt.
  FLAG_TYPES = [:flag, :bool, :boolean]

  # The set of values that indicate a single-parameter (normal) option when
  # passed as the `:type` parameter of #opt.
  #
  # A value of `io` corresponds to a readable IO resource, including
  # a filename, URI, or the strings 'stdin' or '-'.
  SINGLE_ARG_TYPES = [:int, :integer, :string, :double, :float, :io, :date]

  # The set of values that indicate a multiple-parameter option (i.e., that
  # takes multiple space-separated values on the commandline) when passed as
  # the `:type` parameter of #opt.
  MULTI_ARG_TYPES = [:ints, :integers, :strings, :doubles, :floats, :ios, :dates]

  # The complete set of legal values for the `:type` parameter of `#opt`.
  TYPES = FLAG_TYPES + SINGLE_ARG_TYPES + MULTI_ARG_TYPES

  INVALID_SHORT_ARG_REGEX = /[\d-]/

  # @return [Array<String>] Values from the commandline that were not interpreted by `#parse`.
  attr_reader :leftovers

  # The complete configuration hashes for each option. (Mainly useful
  # for testing.)
  attr_reader :specs

  # Initializes the parser.
  #
  # @param args [Array] Arguments for the supplied block.
  def initialize(*args, &block)
    @version = nil
    @leftovers = []
    @specs = {}
    @long = {}
    @short = {}
    @order = []
    @constraints = []
    @stop_words = []
    @stop_on_unknown = false

    cloaker(&block).bind(self).call(*args) if block
  end

  # Define an option.
  #
  # Note that there are two types of argument multiplicity: an argument
  # can take multiple values, e.g. `--arg 1 2 3`. An argument can also
  # be allowed to occur multiple times, e.g. `--arg 1 --arg 2`.
  #
  # Arguments that take multiple values should have a `:type` parameter
  # drawn from `MULTI_ARG_TYPES` (e.g. `:strings`), or a `:default`
  # value of an array of the correct type (e.g. [`String`]). The
  # value of this argument will be an array of the parameters on the
  # commandline.
  #
  # Arguments that can occur multiple times should be marked with
  # `:multi => true`. The value of this argument will also be an array.
  # In contrast with regular non-multi options, if not specified on
  # the commandline, the default value will be `[]`, not `nil`.
  #
  # These two attributes can be combined (e.g. `:type => :strings`,
  # `:multi => true`), in which case the value of the argument will be
  # an array of arrays.
  #
  # There's one ambiguous case to be aware of: when `:multi` is true and a
  # `:default` is set to an array (of something), it's ambiguous whether this
  # is a multi-value argument as well as a multi-occurrence argument.
  # In thise case, Trollop assumes that it's not a multi-value argument.
  # If you want a multi-value, multi-occurrence argument with a default
  # value, you must specify `:type` as well.
  #
  # @param name [String] Name of the option
  # @param desc [String] Description which will be displayed in help messages
  # @param opts [Hash]   Optional parameters
  # @option opts [String] :long Specify the long form of the argument, i.e. the form with two dashes. If unspecified,
  #   will be automatically derived based on the argument name by turning the `name` option into a
  #   string, and replacing any underscores with hyphens.
  # @option opts [String] :short Specify the short form of the argument, i.e. the form with one dash. If unspecified,
  #   will be automatically derived from `name`.
  # @option opts :type Require that the argument take a parameter or parameters of type `type`. For a single
  #   parameter, the value can be a member of `SINGLE_ARG_TYPES`, or a corresponding Ruby class (e.g.
  #   `Integer` for `:int`). For multiple-argument parameters, the value can be any member of
  #   `MULTI_ARG_TYPES` constant. If unset, the default argument type is `:flag`, meaning that the
  #   argument does not take a parameter. The specification of `:type` is not necessary if a
  #   `:default` is given.
  # @option opts :default Set the default value for an argument. Without a default value, the hash returned
  #   by `#parse` (and thus `Trollop::options`) will have a `nil` value for this key unless the argument
  #   is given on the commandline. The argument type is derived automatically from the class of the
  #   default value given, so specifying a `:type` is not necessary if a `:default` is given. (But
  #   see below for an important caveat when `:multi` is specified too.) If the argument is a flag,
  #   and the default is set to `true`, then if it is specified on the the commandline the value will
  #   be `false`.
  # @option opts [Boolean] :required If set to `true`, the argument must be provided on the commandline.
  # @option opts [Boolean] :multi If set to `true`, allows multiple occurrences of the option on the commandline.
  #   Otherwise, only a single instance of the option is allowed. (Note that this is different from
  #   taking multiple parameters.)
  # @raise [ArgumentError] When an option with the given name has already been specified.
  def opt(name, desc="", opts={})
    raise ArgumentError, "you already have an argument named '#{name}'" if @specs.member? name

    ## fill in :type
    opts[:type] = # normalize
      case opts[:type]
      when :boolean, :bool; :flag
      when :integer; :int
      when :integers; :ints
      when :double; :float
      when :doubles; :floats
      when Class
        case opts[:type].name
        when 'TrueClass', 'FalseClass'; :flag
        when 'String'; :string
        when 'Integer'; :int
        when 'Float'; :float
        when 'IO'; :io
        when 'Date'; :date
        else
          raise ArgumentError, "unsupported argument type '#{opts[:type].class.name}'"
        end
      when nil; nil
      else
        raise ArgumentError, "unsupported argument type '#{opts[:type]}'" unless TYPES.include?(opts[:type])
        opts[:type]
      end

    # for options with `:multi => true`, an array default doesn't imply
    # a multi-valued argument. for that you have to specify a `:type`
    # as well. (this is how we disambiguate an ambiguous situation;
    # see the docs for `Parser#opt` for details.)
    disambiguated_default = if opts[:multi] && opts[:default].is_a?(Array) && !opts[:type]
      opts[:default].first
    else
      opts[:default]
    end

    type_from_default =
      case disambiguated_default
      when Integer; :int
      when Numeric; :float
      when TrueClass, FalseClass; :flag
      when String; :string
      when IO; :io
      when Date; :date
      when Array
        if opts[:default].empty?
          raise ArgumentError, "multiple argument type cannot be deduced from an empty array for '#{opts[:default][0].class.name}'"
        end
        case opts[:default][0]    # the first element determines the types
        when Integer; :ints
        when Numeric; :floats
        when String; :strings
        when IO; :ios
        when Date; :dates
        else
          raise ArgumentError, "unsupported multiple argument type '#{opts[:default][0].class.name}'"
        end
      when nil; nil
      else
        raise ArgumentError, "unsupported argument type '#{opts[:default].class.name}'"
      end

    if opts[:type] && type_from_default && opts[:type] != type_from_default
      raise ArgumentError, ":type specification and default type don't match (default type is #{type_from_default})"
    end

    opts[:type] = opts[:type] || type_from_default || :flag

    # fill in :long
    opts[:long] = opts[:long] ? opts[:long].to_s : name.to_s.gsub("_", "-")
    opts[:long] = case opts[:long]
      when /^--([^-].*)$/; $1
      when /^[^-]/; opts[:long]
      else; raise ArgumentError, "invalid long option name #{opts[:long].inspect}"
    end

    if @long[opts[:long]]
      raise ArgumentError, "long option name #{opts[:long].inspect} is already taken; please specify a (different) :long"
    end

    # fill in :short
    opts[:short] = opts[:short].to_s if opts[:short] unless opts[:short] == :none
    opts[:short] = case opts[:short]
      when /^-(.)$/; $1
      when nil, :none, /^.$/; opts[:short]
      else raise ArgumentError, "invalid short option name '#{opts[:short].inspect}'"
    end

    if opts[:short]
      if @short[opts[:short]]
        raise ArgumentError, "short option name #{opts[:short].inspect} is already taken; please specify a (different) :short"
      end

      raise ArgumentError, "a short option name can't be a number or a dash" if opts[:short] =~ INVALID_SHORT_ARG_REGEX
    end

    # fill in :default for flags
    opts[:default] = false if opts[:type] == :flag && opts[:default].nil?

    # autobox :default for :multi (multi-occurrence) arguments
    opts[:default] = [opts[:default]] if opts[:default] && opts[:multi] && !opts[:default].is_a?(Array)

    # fill in :multi
    opts[:multi] ||= false

    opts[:desc] ||= desc
    @long[opts[:long]] = name
    @short[opts[:short]] = name if opts[:short] && opts[:short] != :none
    @specs[name] = opts
    @order << [:opt, name]
  end

  # Sets the version string. If set, the user can request the version
  # on the commandline. Should probably be of the form "<program name>
  # <version number>".
  #
  # @param text [String] Version string of the program.
  # @return [String] Version string of the program.
  def version(text = nil)
    @version ||= text
  end

  # Adds text to the help display. Can be interspersed with calls to
  # `#opt` to build a multi-section help page.
  #
  # @param text [String] Additional help text to display for the user.
  # @return [void]
  def banner(text)
    @order << [:text, text]
  end
  alias :text :banner

  # Marks two (or more!) options as requiring each other. Only handles
  # undirected (i.e., mutual) dependencies. Directed dependencies are
  # better modeled with `Trollop::die`.
  #
  # @param symbols [Array<Symbol>] Options that require each other.
  # @return [void]
  def depends(*symbols)
    symbols.each { |sym| raise ArgumentError, "unknown option '#{sym}'" unless @specs[sym] }

    @constraints << [:depends, symbols]
  end

  # Marks two (or more!) options as conflicting.
  #
  # @param symbols [Array<Symbol>] Options that conflict with each other.
  # @return [void]
  def conflicts(*symbols)
    symbols.each { |sym| raise ArgumentError, "unknown option '#{sym}'" unless @specs[sym] }

    @constraints << [:conflicts, symbols]
  end

  # Defines a set of words which cause parsing to terminate when
  # encountered, such that any options to the left of the word are
  # parsed as usual, and options to the right of the word are left
  # intact.
  #
  # A typical use case would be for subcommand support, where these
  # would be set to the list of subcommands. A subsequent Trollop
  # invocation would then be used to parse subcommand options, after
  # shifting the subcommand off of `ARGV`.
  #
  # @param words [Array<String>] Words that will stop argument parsing.
  # @return [void]
  def stop_on(*words)
    @stop_words = [*words].flatten
  end

  # Similar to `#stop_on`, but stops on any unknown word when encountered
  # (unless it is a parameter for an argument). This is useful for
  # cases where you don't know the set of subcommands ahead of time,
  # i.e., without first parsing the global options.
  #
  # @see stop_on
  # @return [void]
  def stop_on_unknown
    @stop_on_unknown = true
  end

  # Parses the commandline. Typically called by `Trollop::options`,
  # but you can call it directly if you need more control.
  #
  # @param cmdline [Array<String>] List of command-line arguments.
  # @return [Hash] Hash containing options and values.
  # @raise [CommandlineError] When the command-line is malformed.
  # @raise [HelpNeeded] When help is requested by the user.
  # @raise [VersionNeeded] When the version information is requested by the user.
  def parse(cmdline = ARGV)
    vals = {}
    required = {}

    opt :version, "Print version and exit" if @version unless @specs[:version] || @long["version"]
    opt :help, "Show this message" unless @specs[:help] || @long["help"]

    @specs.each do |sym, opts|
      required[sym] = true if opts[:required]
      vals[sym] = opts[:default]
      vals[sym] = [] if opts[:multi] && !opts[:default] # multi arguments default to [], not nil
    end

    resolve_default_short_options!

    # resolve symbols
    given_args = {}
    @leftovers = each_arg cmdline do |arg, params|
      # handle --no- forms
      arg, negative_given = if arg =~ /^--no-([^-]\S*)$/
        ["--#{$1}", true]
      else
        [arg, false]
      end

      sym = case arg
        when /^-([^-])$/; @short[$1]
        when /^--([^-]\S*)$/; @long[$1] || @long["no-#{$1}"]
        else; raise CommandlineError, "invalid argument syntax: '#{arg}'"
      end

      sym = nil if arg =~ /--no-/ # explicitly invalidate --no-no- arguments

      raise CommandlineError, "unknown argument '#{arg}'" unless sym

      if given_args.include?(sym) && !@specs[sym][:multi]
        raise CommandlineError, "option '#{arg}' specified multiple times"
      end

      given_args[sym] ||= {}
      given_args[sym][:arg] = arg
      given_args[sym][:negative_given] = negative_given
      given_args[sym][:params] ||= []

      # The block returns the number of parameters taken.
      num_params_taken = 0

      unless params.nil?
        if SINGLE_ARG_TYPES.include?(@specs[sym][:type])
          given_args[sym][:params] << params[0, 1]  # take the first parameter
          num_params_taken = 1
        elsif MULTI_ARG_TYPES.include?(@specs[sym][:type])
          given_args[sym][:params] << params        # take all the parameters
          num_params_taken = params.size
        end
      end

      num_params_taken
    end

    # check for version and help args
    raise VersionNeeded if given_args.include? :version
    raise HelpNeeded if given_args.include? :help

    # check constraint satisfaction
    @constraints.each do |type, syms|
      constraint_sym = syms.find { |sym| given_args[sym] }
      next unless constraint_sym

      case type
      when :depends
        syms.each do |sym|
          unless given_args.include? sym
            raise CommandlineError, "--#{@specs[constraint_sym][:long]} requires --#{@specs[sym][:long]}"
          end
        end
      when :conflicts
        syms.each do |sym|
          if given_args.include?(sym) && (sym != constraint_sym)
            raise CommandlineError, "--#{@specs[constraint_sym][:long]} conflicts with --#{@specs[sym][:long]}"
          end
        end
      end
    end

    required.each do |sym, val|
      raise CommandlineError, "option --#{@specs[sym][:long]} must be specified" unless given_args.include? sym
    end

    # parse parameters
    given_args.each do |sym, given_data|
      arg, params, negative_given = given_data.values_at :arg, :params, :negative_given

      opts = @specs[sym]
      raise CommandlineError, "option '#{arg}' needs a parameter" if params.empty? && opts[:type] != :flag

      vals["#{sym}_given".intern] = true # mark argument as specified on the commandline

      case opts[:type]
      when :flag
        vals[sym] = (sym.to_s =~ /^no_/ ? negative_given : !negative_given)
      when :int, :ints
        vals[sym] = params.map { |pg| pg.map { |p| parse_integer_parameter p, arg } }
      when :float, :floats
        vals[sym] = params.map { |pg| pg.map { |p| parse_float_parameter p, arg } }
      when :string, :strings
        vals[sym] = params.map { |pg| pg.map { |p| p.to_s } }
      when :io, :ios
        vals[sym] = params.map { |pg| pg.map { |p| parse_io_parameter p, arg } }
      when :date, :dates
        vals[sym] = params.map { |pg| pg.map { |p| parse_date_parameter p, arg } }
      end

      if SINGLE_ARG_TYPES.include?(opts[:type])
        unless opts[:multi]       # single parameter
          vals[sym] = vals[sym][0][0]
        else                      # multiple options, each with a single parameter
          vals[sym] = vals[sym].map { |p| p[0] }
        end
      elsif MULTI_ARG_TYPES.include?(opts[:type]) && !opts[:multi]
        vals[sym] = vals[sym][0]  # single option, with multiple parameters
      end
      # else: multiple options, with multiple parameters
    end

    # modify input in place with only those
    # arguments we didn't process
    cmdline.clear
    @leftovers.each { |l| cmdline << l }

    # allow openstruct-style accessors
    class << vals
      def method_missing(m, *args)
        self[m] || self[m.to_s]
      end
    end
    vals
  end

  # Parses a date parameter.
  #
  # @note Will use the [Chronic](https://github.com/mojombo/chronic) gem if it is installed
  #       and loaded.
  #
  # @param param [String] Value to be parsed.
  # @param arg [Symbol] Name of the option.
  # @return [Date] Parsed date information.
  # @raise [CommandLineError] When no value is supplied or is not recognizable as a date.
  def parse_date_parameter(param, arg)
    begin
      begin
        time = Chronic.parse(param)
      rescue NameError
        # chronic is not available
      end
      time ? Date.new(time.year, time.month, time.day) : Date.parse(param)
    rescue ArgumentError
      raise CommandlineError, "option '#{arg}' needs a date"
    end
  end

  # Print the help message to `stream`.
  #
  # @param stream [IO] Stream to use for output of the help message.
  # @return [void]
  def educate(stream = $stdout)
    width # hack: calculate it now; otherwise we have to be careful not to
          # call this unless the cursor's at the beginning of a line.
    left = {}
    @specs.each do |name, spec|
      left[name] = "--#{spec[:long]}" +
        (spec[:type] == :flag && spec[:default] ? ", --no-#{spec[:long]}" : "") +
        (spec[:short] && spec[:short] != :none ? ", -#{spec[:short]}" : "") +
        case spec[:type]
        when :flag; ""
        when :int; " <i>"
        when :ints; " <i+>"
        when :string; " <s>"
        when :strings; " <s+>"
        when :float; " <f>"
        when :floats; " <f+>"
        when :io; " <filename/uri>"
        when :ios; " <filename/uri+>"
        when :date; " <date>"
        when :dates; " <date+>"
        end
    end

    leftcol_width = left.values.map { |s| s.length }.max || 0
    rightcol_start = leftcol_width + 6 # spaces

    unless @order.size > 0 && @order.first.first == :text
      stream.puts "#@version\n" if @version
      stream.puts "Options:"
    end

    @order.each do |what, opt|
      if what == :text
        stream.puts wrap(opt)
        next
      end

      spec = @specs[opt]
      stream.printf "  %#{leftcol_width}s:   ", left[opt]
      desc = spec[:desc] + begin
        default_s = case spec[:default]
        when $stdout; "<stdout>"
        when $stdin; "<stdin>"
        when $stderr; "<stderr>"
        when Array
          spec[:default].join(", ")
        else
          spec[:default].to_s
        end

        if spec[:default]
          if spec[:desc] =~ /\.$/
            " (Default: #{default_s})"
          else
            " (default: #{default_s})"
          end
        else
          ""
        end
      end
      stream.puts wrap(desc, :width => width - rightcol_start - 1, :prefix => rightcol_start)
    end
  end

  # Calculates the screen width for proper wrapping of output.
  #
  # @return [Integer] Screen width in characters.
  def width
    @width ||= if $stdout.tty?
      begin
        require 'curses'
        Curses::init_screen
        x = Curses::cols
        Curses::close_screen
        x
      rescue Exception
        80
      end
    else
      80
    end
  end

  # Splits the text into chunks that will fit the output width.
  #
  # @param [String] str Text to wrap.
  # @param [Hash] opts Options for the wrapping.
  # @return [Array<String>] Chunks of text equal to or shorter than the output width.
  def wrap(str, opts = {})
    if str == ""
      [""]
    else
      str.split("\n").map { |s| wrap_line s, opts }.flatten
    end
  end

  # The per-parser version of `Trollop::die`.
  #
  # @param arg [Symbol] Argument that caused the error.
  # @param msg [String] Message describing the error.
  # @return [void]
  # @see Trollop.die
  def die(arg, msg)
    if msg
      $stderr.puts "Error: argument --#{@specs[arg][:long]} #{msg}."
    else
      $stderr.puts "Error: #{arg}."
    end
    $stderr.puts "Try --help for help."
    exit(-1)
  end

private

  # yield successive arg, parameter pairs
  def each_arg(args)
    remains = []
    i = 0

    until i >= args.length
      if @stop_words.member? args[i]
        remains += args[i .. -1]
        return remains
      end
      case args[i]
      when /^--$/ # arg terminator
        remains += args[(i + 1) .. -1]
        return remains
      when /^--(\S+?)=(.*)$/ # long argument with equals
        yield "--#{$1}", [$2]
        i += 1
      when /^--(\S+)$/ # long argument
        params = collect_argument_parameters(args, i + 1)
        unless params.empty?
          num_params_taken = yield args[i], params
          unless num_params_taken
            if @stop_on_unknown
              remains += args[i + 1 .. -1]
              return remains
            else
              remains += params
            end
          end
          i += 1 + num_params_taken
        else # long argument no parameter
          yield args[i], nil
          i += 1
        end
      when /^-(\S+)$/ # one or more short arguments
        shortargs = $1.split(//)
        shortargs.each_with_index do |a, j|
          if j == (shortargs.length - 1)
            params = collect_argument_parameters(args, i + 1)
            unless params.empty?
              num_params_taken = yield "-#{a}", params
              unless num_params_taken
                if @stop_on_unknown
                  remains += args[i + 1 .. -1]
                  return remains
                else
                  remains += params
                end
              end
              i += 1 + num_params_taken
            else # argument no parameter
              yield "-#{a}", nil
              i += 1
            end
          else
            yield "-#{a}", nil
          end
        end
      else
        if @stop_on_unknown
          remains += args[i .. -1]
          return remains
        else
          remains << args[i]
          i += 1
        end
      end
    end

    remains
  end

  def parse_integer_parameter(param, arg)
    raise CommandlineError, "option '#{arg}' needs an integer" unless param =~ /^\d+$/
    param.to_i
  end

  def parse_float_parameter(param, arg)
    raise CommandlineError, "option '#{arg}' needs a floating-point number" unless param =~ FLOAT_RE
    param.to_f
  end

  def parse_io_parameter(param, arg)
    case param
    when /^(stdin|-)$/i; $stdin
    else
      require 'open-uri'
      begin
        open param
      rescue SystemCallError => e
        raise CommandlineError, "file or url for option '#{arg}' cannot be opened: #{e.message}"
      end
    end
  end

  def collect_argument_parameters(args, start_at)
    params = []
    pos = start_at
    while args[pos] && args[pos] !~ PARAM_RE && !@stop_words.member?(args[pos]) do
      params << args[pos]
      pos += 1
    end
    params
  end

  def resolve_default_short_options!
    @order.each do |type, name|
      next unless type == :opt
      opts = @specs[name]
      next if opts[:short]

      c = opts[:long].split(//).find { |d| d !~ INVALID_SHORT_ARG_REGEX && !@short.member?(d) }
      if c # found a character to use
        opts[:short] = c
        @short[c] = name
      end
    end
  end

  def wrap_line(str, opts = {})
    prefix = opts[:prefix] || 0
    width = opts[:width] || (self.width - 1)
    start = 0
    ret = []
    until start > str.length
      nextt =
        if start + width >= str.length
          str.length
        else
          x = str.rindex(/\s/, start + width)
          x = str.index(/\s/, start) if x && x < start
          x || str.length
        end
      ret << (ret.empty? ? "" : " " * prefix) + str[start ... nextt]
      start = nextt + 1
    end
    ret
  end

  # instance_eval but with ability to handle block arguments
  # thanks to _why: http://redhanded.hobix.com/inspect/aBlockCostume.html
  def cloaker(&b)
    (class << self; self; end).class_eval do
      define_method :cloaker_, &b
      meth = instance_method :cloaker_
      remove_method :cloaker_
      meth
    end
  end
end

# The easy, syntactic-sugary entry method into Trollop. Creates a Parser,
# passes the block to it, then parses `args` with it, handling any errors or
# requests for help or version information appropriately (and then exiting).
# Modifies `args` in place. Returns a hash of option values.
#
# The block passed in should contain zero or more calls to `opt`
# (`Parser#opt`), zero or more calls to `text` (`Parser#text`), and
# probably a call to `version` (`Parser#version`).
#
# The returned block contains a value for every option specified with
# `opt`.  The value will be the value given on the commandline, or the
# default value if the option was not specified on the commandline. For
# every option specified on the commandline, a key `<option
# name>_given` will also be set in the hash.
#
# @example
#
#   require 'trollop'
#   opts = Trollop::options do
#     opt :monkey, "Use monkey mode"                    # a flag --monkey, defaulting to false
#     opt :name, "Monkey name", :type => :string        # a string --name <s>, defaulting to nil
#     opt :num_limbs, "Number of limbs", :default => 4  # an integer --num-limbs <i>, defaulting to 4
#   end
#
#   # if called with no arguments
#   p opts # => {:monkey=>false, :name=>nil, :num_limbs=>4, :help=>false}
#
#   # if called with --monkey
#   p opts # => {:monkey=>true, :name=>nil, :num_limbs=>4, :help=>false, :monkey_given=>true}
#
# @param [Array<String>] args Command-line arguments.
# @param [Array] a Arguments to pass to the block.
# @return [Hash] Hash containing options and values.
# @see http://trollop.rubyforge.org More examples
def options(args = ARGV, *a, &b)
  @last_parser = Parser.new(*a, &b)
  with_standard_exception_handling(@last_parser) { @last_parser.parse args }
end

# If `Trollop::options` doesn't do quite what you want, you can create a `Parser`
# object and call `Parser#parse` on it. That method will throw `CommandlineError`,
# `HelpNeeded` and `VersionNeeded` exceptions when necessary; if you want to
# have these handled for you in the standard manner (e.g. show the help
# and then exit upon an `HelpNeeded` exception), call your code from within
# a block passed to this method.
#
# Note that this method will call `System#exit` after handling an exception!
#
# @example
#
#   require 'trollop'
#   p = Trollop::Parser.new do
#     opt :monkey, "Use monkey mode"                     # a flag --monkey, defaulting to false
#     opt :goat, "Use goat mode", :default => true       # a flag --goat, defaulting to true
#   end
#
#   opts = Trollop::with_standard_exception_handling p do
#     o = p.parse ARGV
#     raise Trollop::HelpNeeded if ARGV.empty? # show help screen
#     o
#   end
#
# Requires passing in the parser object.
# @param [Parser] parser Parser to use to handle the command-line arguments.
# @return [Hash] Hash containing options and values.
def with_standard_exception_handling(parser)
  begin
    yield
  rescue CommandlineError => e
    $stderr.puts "Error: #{e.message}."
    $stderr.puts "Try --help for help."
    exit(-1)
  rescue HelpNeeded
    parser.educate
    exit
  rescue VersionNeeded
    puts parser.version
    exit
  end
end

# Notifies the user of a problem with argument parsing and exits the application.
#
# @example Supply both argument and message
#
#   options do
#     opt :volume, :default => 0.0
#   end
#
#   die :volume, "too loud" if opts[:volume] > 10.0
#   die :volume, "too soft" if opts[:volume] < 0.1
#
# @example Or supply just the message
#
#   options do
#     opt :whatever # ...
#   end
#
#   Trollop::die "need at least one filename" if ARGV.empty?
#
# @overload die(arg, msg)
# @overload die(msg)
# @param [Symbol] arg Argument that is at issue.
# @param [String] msg Message describing the problem.
# @return [void]
# @raise [ArgumentError] When `Trollop::die` is called before calling `Trollop::options`.
def die(arg, msg = nil)
  if @last_parser
    @last_parser.die arg, msg
  else
    raise ArgumentError, "Trollop::die can only be called after Trollop::options"
  end
end

module_function :options, :die, :with_standard_exception_handling

end # module
