shflags

# $Id$
# vim:et:ft=sh:sts=2:sw=2
#
# Copyright 2008 Kate Ward. All Rights Reserved.
# Released under the LGPL (GNU Lesser General Public License)
#
# shFlags -- Advanced command-line flag library for Unix shell scripts
#
# Author: kate.ward@forestent.com (Kate Ward)
#
# This module implements something like the google-gflags library available
# from http://code.google.com/p/google-gflags/.
#
# FLAG TYPES: This is a list of the DEFINE_*'s that you can do.  All flags take
# a name, default value, help-string, and optional 'short' name (one-letter
# name).  Some flags have other arguments, which are described with the flag.
#
# DEFINE_string: takes any input, and intreprets it as a string.
#
# DEFINE_boolean: typically does not take any argument: say --myflag to set
#   FLAGS_myflag to true, or --nomyflag to set FLAGS_myflag to false.
#   Alternately, you can say
#     --myflag=true  or --myflag=t or --myflag=0  or
#     --myflag=false or --myflag=f or --myflag=1
#   Passing an option has the same affect as passing the option once.
#
# DEFINE_float: takes an input and intreprets it as a floating point number. As
#   shell does not support floats per-se, the input is merely validated as
#   being a valid floating point value.
#
# DEFINE_integer: takes an input and intreprets it as an integer.
#
# SPECIAL FLAGS: There are a few flags that have special meaning:
#   --help (or -?)  prints a list of all the flags in a human-readable fashion
#   --flagfile=foo  read flags from foo.
#   --              as in getopt(), terminates flag-processing
#
# EXAMPLE USAGE:
#
#   #! /bin/sh
#   . ./shflags
#
#   DEFINE_string name 'world' "somebody's name"
#   FLAGS "$@" || exit $?; shift ${FLAGS_ARGC}
#   echo "Hello, ${FLAGS_name}."
#
# NOTE: Not all systems include a getopt version that supports long flags. On
# these systems, only short flags are recognized.

#==============================================================================
# shFlags
#
# Shared attributes:
#   flags_error: last error message
#   flags_return: last return value
#
#   __flags_longNames: list of long names for all flags
#   __flags_shortNames: list of short names for all flags
#   __flags_boolNames: list of boolean flag names
#
#   __flags_opts: options parsed by getopt
#
# Per-flag attributes:
#   FLAGS_<flag_name>: contains value of flag named 'flag_name'
#   __flags_<flag_name>_default: the default flag value
#   __flags_<flag_name>_help: the flag help string
#   __flags_<flag_name>_short: the flag short name
#   __flags_<flag_name>_type: the flag type
#
# Notes:
# - lists of strings are space separated, and a null value is the '~' char.

# return if FLAGS already loaded
[ -n "${FLAGS_VERSION:-}" ] && return 0
FLAGS_VERSION='1.0.2pre'

FLAGS_TRUE=0
FLAGS_FALSE=1
FLAGS_ERROR=2

_flags_debug() { echo "flags:DEBUG $@" >&2; }
_flags_warn() { echo "flags:WARN $@" >&2; }
_flags_error() { echo "flags:ERROR $@" >&2; }
_flags_fatal() { echo "flags:FATAL $@" >&2; }

# specific shell checks
if [ -n "${ZSH_VERSION:-}" ]; then
  setopt |grep "^shwordsplit$" >/dev/null
  if [ $? -ne ${FLAGS_TRUE} ]; then
    _flags_fatal 'zsh shwordsplit option is required for proper zsh operation'
    exit ${FLAGS_ERROR}
  fi
  if [ -z "${FLAGS_PARENT:-}" ]; then
    _flags_fatal "zsh does not pass \$0 through properly. please declare' \
\"FLAGS_PARENT=\$0\" before calling shFlags"
    exit ${FLAGS_ERROR}
  fi
fi

# shell flags
#  u: treat unset variables as an error when performing parameter expansion
__FLAGS_SHELL_FLAGS='u'

# save the current set of shell flags, and then set some for ourself
__flags_oldShellFlags=$-
for __flags_shellFlag in `echo "${__FLAGS_SHELL_FLAGS}" |sed 's/\(.\)/\1 /g'`
do
  set "-${__flags_shellFlag}"
done

#
# constants
#

# getopt version
__FLAGS_GETOPT_VERS_STD=0
__FLAGS_GETOPT_VERS_ENH=1
__FLAGS_GETOPT_VERS_BSD=2

getopt >/dev/null 2>&1
case $? in
  0) __FLAGS_GETOPT_VERS=${__FLAGS_GETOPT_VERS_STD} ;;  # bsd getopt
  2)
    if [ "`getopt --version`" = '-- ' ]; then
      __FLAGS_GETOPT_VERS=${__FLAGS_GETOPT_VERS_STD}
    else
      __FLAGS_GETOPT_VERS=${__FLAGS_GETOPT_VERS_ENH}
    fi
    ;;
  *)
    _flags_fatal 'unable to determine getopt version'
    exit ${FLAGS_ERROR}
    ;;
esac

# getopt optstring lengths
__FLAGS_OPTSTR_SHORT=0
__FLAGS_OPTSTR_LONG=1

__FLAGS_NULL='~'

# flag info strings
__FLAGS_INFO_DEFAULT_STR='default'
__FLAGS_INFO_HELP_STR='help'
__FLAGS_INFO_SHORT_STR='short'
__FLAGS_INFO_TYPE_STR='type'

# flag lengths
__FLAGS_LEN_SHORT=0
__FLAGS_LEN_LONG=1

# flag types
__FLAGS_TYPE_NONE=0
__FLAGS_TYPE_BOOLEAN=1
__FLAGS_TYPE_FLOAT=2
__FLAGS_TYPE_INTEGER=3
__FLAGS_TYPE_STRING=4

# set the constants readonly
_flags_constants=`set |awk -F= '/^FLAGS_/ || /^__FLAGS_/ {print $1}'`
for _flags_const in ${_flags_constants}; do
  if [ -n "${ZSH_VERSION:-}" ]; then
    case ${ZSH_VERSION} in
      [123].*) readonly ${_flags_const} ;;
      *) readonly -g ${_flags_const} ;;  # declare readonly constants globally
    esac
  else
    readonly ${_flags_const}
  fi
done
unset _flags_const _flags_constants

#
# internal variables
#

__flags_boolNames=' '
__flags_longNames=' '
__flags_shortNames=' '

__flags_opts=''

# restore the previous set of shell flags
for __flags_shellFlag in ${__FLAGS_SHELL_FLAGS}; do
  echo ${__flags_oldShellFlags} \
  |grep ${__flags_shellFlag} >/dev/null || set +${__flags_shellFlag}
done
unset __flags_oldShellFlags __flags_shellFlag

#------------------------------------------------------------------------------
# private functions
#

# Define a flag.
#
# Calling this function will define the following info variables for the
# specified flag:
#   FLAGS_flagname - the name for this flag (based upon the long flag name)
#   __flags_<flag_name>_default - the default value
#   __flags_flagname_help - the help string
#   __flags_flagname_short - the single letter alias
#   __flags_flagname_type - the type of flag (one of __FLAGS_TYPE_*)
#
# Args:
#   _flags__type: integer: internal type of flag (__FLAGS_TYPE_*)
#   _flags__name: string: long flag name
#   _flags__default: default flag value
#   _flags__help: string: help string
#   _flags__short: string: (optional) short flag name
# Returns:
#   integer: success of operation, or error
_flags_define()
{
  if [ $# -lt 4 ]; then
    flags_error='DEFINE error: too few arguments'
    flags_return=${FLAGS_ERROR}
    _flags_error "${flags_error}"
    return ${flags_return}
  fi

  _flags_type_=$1
  _flags_name_=$2
  _flags_default_=$3
  _flags_help_=$4
  _flags_short_=${5:-${__FLAGS_NULL}}

  _flags_return_=${FLAGS_TRUE}

  # TODO(kward): check for validity of the flag name (e.g. dashes)

  # require short option for getopt that don't support long options
  if [ ${_flags_return_} -eq ${FLAGS_TRUE} \
      -a ${__FLAGS_GETOPT_VERS} -ne ${__FLAGS_GETOPT_VERS_ENH} \
      -a "${_flags_short_}" = "${__FLAGS_NULL}" ]
  then
    flags_error="short flag required for (${_flags_name_}) on this platform"
    _flags_return_=${FLAGS_ERROR}
  fi

  # check for existing long name definition
  if [ ${_flags_return_} -eq ${FLAGS_TRUE} ]; then
    if _flags_itemInList "${_flags_name_}" \
        ${__flags_longNames} ${__flags_boolNames}
    then
      flags_error="flag name ([no]${_flags_name_}) already defined"
      _flags_warn "${flags_error}"
      _flags_return_=${FLAGS_FALSE}
    fi
  fi

  # check for existing short name definition
  if [ ${_flags_return_} -eq ${FLAGS_TRUE} \
      -a "${_flags_short_}" != "${__FLAGS_NULL}" ]
  then
    if _flags_itemInList "${_flags_short_}" ${__flags_shortNames}; then
      flags_error="flag short name (${_flags_short_}) already defined"
      _flags_warn "${flags_error}"
      _flags_return_=${FLAGS_FALSE}
    fi
  fi

  # handle default value. note, on several occasions the 'if' portion of an
  # if/then/else contains just a ':' which does nothing. a binary reversal via
  # '!' is not done because it does not work on all shells.
  if [ ${_flags_return_} -eq ${FLAGS_TRUE} ]; then
    case ${_flags_type_} in
      ${__FLAGS_TYPE_BOOLEAN})
        if _flags_validateBoolean "${_flags_default_}"; then
          case ${_flags_default_} in
            true|t|0) _flags_default_=${FLAGS_TRUE} ;;
            false|f|1) _flags_default_=${FLAGS_FALSE} ;;
          esac
        else
          flags_error="invalid default flag value '${_flags_default_}'"
          _flags_return_=${FLAGS_ERROR}
        fi
        ;;

      ${__FLAGS_TYPE_FLOAT})
        if _flags_validateFloat "${_flags_default_}"; then
          :
        else
          flags_error="invalid default flag value '${_flags_default_}'"
          _flags_return_=${FLAGS_ERROR}
        fi
        ;;

      ${__FLAGS_TYPE_INTEGER})
        if _flags_validateInteger "${_flags_default_}"; then
          :
        else
          flags_error="invalid default flag value '${_flags_default_}'"
          _flags_return_=${FLAGS_ERROR}
        fi
        ;;

      ${__FLAGS_TYPE_STRING}) ;;  # everything in shell is a valid string

      *)
        flags_error="unrecognized flag type '${_flags_type_}'"
        _flags_return_=${FLAGS_ERROR}
        ;;
    esac
  fi

  if [ ${_flags_return_} -eq ${FLAGS_TRUE} ]; then
    # store flag information
    eval "FLAGS_${_flags_name_}='${_flags_default_}'"
    eval "__flags_${_flags_name_}_${__FLAGS_INFO_TYPE_STR}=${_flags_type_}"
    eval "__flags_${_flags_name_}_${__FLAGS_INFO_DEFAULT_STR}=\
\"${_flags_default_}\""
    eval "__flags_${_flags_name_}_${__FLAGS_INFO_HELP_STR}=\"${_flags_help_}\""
    eval "__flags_${_flags_name_}_${__FLAGS_INFO_SHORT_STR}='${_flags_short_}'"

    # append flag name(s) to list of names
    __flags_longNames="${__flags_longNames}${_flags_name_} "
    __flags_shortNames="${__flags_shortNames}${_flags_short_} "
    [ ${_flags_type_} -eq ${__FLAGS_TYPE_BOOLEAN} ] && \
        __flags_boolNames="${__flags_boolNames}no${_flags_name_} "
  fi

  flags_return=${_flags_return_}
  unset _flags_default_ _flags_help_ _flags_name_ _flags_return_ _flags_short_ \
      _flags_type_
  [ ${flags_return} -eq ${FLAGS_ERROR} ] && _flags_error "${flags_error}"
  return ${flags_return}
}

# Return valid getopt options using currently defined list of long options.
#
# This function builds a proper getopt option string for short (and long)
# options, using the current list of long options for reference.
#
# Args:
#   _flags_optStr: integer: option string type (__FLAGS_OPTSTR_*)
# Output:
#   string: generated option string for getopt
# Returns:
#   boolean: success of operation (always returns True)
_flags_genOptStr()
{
  _flags_optStrType_=$1

  _flags_opts_=''

  for _flags_flag_ in ${__flags_longNames}; do
    _flags_type_=`_flags_getFlagInfo ${_flags_flag_} ${__FLAGS_INFO_TYPE_STR}`
    case ${_flags_optStrType_} in
      ${__FLAGS_OPTSTR_SHORT})
        _flags_shortName_=`_flags_getFlagInfo \
            ${_flags_flag_} ${__FLAGS_INFO_SHORT_STR}`
        if [ "${_flags_shortName_}" != "${__FLAGS_NULL}" ]; then
          _flags_opts_="${_flags_opts_}${_flags_shortName_}"
          # getopt needs a trailing ':' to indicate a needed option
          [ ${_flags_type_} -ne ${__FLAGS_TYPE_BOOLEAN} ] && \
              _flags_opts_="${_flags_opts_}:"
        fi
        ;;

      ${__FLAGS_OPTSTR_LONG})
        _flags_opts_="${_flags_opts_:+${_flags_opts_},}${_flags_flag_}"
        # getopt needs a trailing ':' to indicate a needed option
        [ ${_flags_type_} -ne ${__FLAGS_TYPE_BOOLEAN} ] && \
            _flags_opts_="${_flags_opts_}:"
        ;;
    esac
  done

  echo "${_flags_opts_}"
  unset _flags_flag_ _flags_opts_ _flags_optStrType_ _flags_shortName_ \
      _flags_type_
  return ${FLAGS_TRUE}
}

# Returns flag details based on a flag name and flag info.
#
# Args:
#   string: long flag name
#   string: flag info (see the _flags_define function for valid info types)
# Output:
#   string: value of dereferenced flag variable
# Returns:
#   integer: one of FLAGS_{TRUE|FALSE|ERROR}
_flags_getFlagInfo()
{
  _flags_name_=$1
  _flags_info_=$2

  _flags_nameVar_="__flags_${_flags_name_}_${_flags_info_}"
  _flags_strToEval_="_flags_value_=\"\${${_flags_nameVar_}:-}\""
  eval "${_flags_strToEval_}"
  if [ -n "${_flags_value_}" ]; then
    flags_return=${FLAGS_TRUE}
  else
    # see if the _flags_name_ variable is a string as strings can be empty...
    # note: the DRY principle would say to have this function call itself for
    # the next three lines, but doing so results in an infinite loop as an
    # invalid _flags_name_ will also not have the associated _type variable.
    # Because it doesn't (it will evaluate to an empty string) the logic will
    # try to find the _type variable of the _type variable, and so on. Not so
    # good ;-)
    _flags_typeVar_="__flags_${_flags_name_}_${__FLAGS_INFO_TYPE_STR}"
    _flags_strToEval_="_flags_type_=\"\${${_flags_typeVar_}:-}\""
    eval "${_flags_strToEval_}"
    if [ "${_flags_type_}" = "${__FLAGS_TYPE_STRING}" ]; then
      flags_return=${FLAGS_TRUE}
    else
      flags_return=${FLAGS_ERROR}
      flags_error="invalid flag name (${_flags_nameVar_})"
    fi
  fi

  echo "${_flags_value_}"
  unset _flags_info_ _flags_name_ _flags_strToEval_ _flags_type_ _flags_value_ \
      _flags_nameVar_ _flags_typeVar_
  [ ${flags_return} -eq ${FLAGS_ERROR} ] && _flags_error "${flags_error}"
  return ${flags_return}
}

# check for presense of item in a list. passed a string (e.g. 'abc'), this
# function will determine if the string is present in the list of strings (e.g.
# ' foo bar abc ').
#
# Args:
#   _flags__str: string: string to search for in a list of strings
#   unnamed: list: list of strings
# Returns:
#   boolean: true if item is in the list
_flags_itemInList()
{
  _flags_str_=$1
  shift

  echo " ${*:-} " |grep " ${_flags_str_} " >/dev/null
  if [ $? -eq 0 ]; then
    flags_return=${FLAGS_TRUE}
  else
    flags_return=${FLAGS_FALSE}
  fi

  unset _flags_str_
  return ${flags_return}
}

# Returns the width of the current screen.
#
# Output:
#   integer: width in columns of the current screen.
_flags_screenColumns()
{
  if _flags_size_=`stty size 2>/dev/null`; then
    # stty size worked :-)
    _flags_cols_=`expr "${_flags_size_}" : '[0-9]* \([0-9]*\)'`
  elif _flags_cols_=`tput cols 2>/dev/null`; then
    # TODO(kward): this doesn't actaully work... tput is executed within a
    # sub-shell which causes the screen width to be lost.
    :  # tput worked :-)
  else
    _flags_cols_=80
  fi
  echo ${_flags_cols_}
  unset _flags_cols_ _flags_size_
}

# Validate a boolean.
#
# Args:
#   _flags__bool: boolean: value to validate
# Returns:
#   bool: true if the value is a valid boolean
_flags_validateBoolean()
{
  _flags_bool_=$1

  flags_return=${FLAGS_TRUE}
  case "${_flags_bool_}" in
    true|t|0) ;;
    false|f|1) ;;
    *) flags_return=${FLAGS_FALSE} ;;
  esac

  unset _flags_bool_
  return ${flags_return}
}

# Validate a float.
#
# Args:
#   _flags__float: float: value to validate
# Returns:
#   bool: true if the value is a valid float
_flags_validateFloat()
{
  _flags_float_=$1

  if _flags_validateInteger ${_flags_float_}; then
    flags_return=${FLAGS_TRUE}
  else
    flags_return=${FLAGS_TRUE}
    case ${_flags_float_} in
      -*)  # negative floats
        _flags_test_=`expr "${_flags_float_}" : '\(-[0-9][0-9]*\.[0-9][0-9]*\)'`
        ;;
      *)  # positive floats
        _flags_test_=`expr "${_flags_float_}" : '\([0-9][0-9]*\.[0-9][0-9]*\)'`
        ;;
    esac
    [ "${_flags_test_}" != "${_flags_float_}" ] && flags_return=${FLAGS_FALSE}
  fi

  unset _flags_float_ _flags_test_
  return ${flags_return}
}

# Validate an integer.
#
# Args:
#   _flags__integer: interger: value to validate
# Returns:
#   bool: true if the value is a valid integer
_flags_validateInteger()
{
  _flags_int_=$1

  flags_return=${FLAGS_TRUE}
  case ${_flags_int_} in
    -*)  # negative ints
      _flags_test_=`expr "${_flags_int_}" : '\(-[0-9][0-9]*\)'`
      ;;
    *)  # positive ints
      _flags_test_=`expr "${_flags_int_}" : '\([0-9][0-9]*\)'`
      ;;
  esac
  [ "${_flags_test_}" != "${_flags_int_}" ] && flags_return=${FLAGS_FALSE}

  unset _flags_int_ _flags_test_
  return ${flags_return}
}

# Parse command-line options using the standard getopt.
#
# Note: the flag options are passed around in the global __flags_opts so that
# the formatting is not lost due to shell parsing and such.
#
# Args:
#   @: varies: command-line options to parse
# Returns:
#   integer: a FLAGS success condition
_flags_standardGetopt()
{
  flags_return=${FLAGS_TRUE}
  _flags_shortOpts_=`_flags_genOptStr ${__FLAGS_OPTSTR_SHORT}`

  # check for spaces in passed options
  for _flags_opt_ in "$@"; do
    _flags_match_=`echo "${_flags_opt_}" |sed 's/ //g'`
    if [ "${_flags_match_}" != "${_flags_opt_}" ]; then
      flags_error='the available getopt does not support spaces in options'
      flags_return=${FLAGS_ERROR}
      break
    fi
  done

  if [ ${flags_return} -eq ${FLAGS_TRUE} ]; then
    __flags_opts=`getopt ${_flags_shortOpts_} $@ 2>&1`
    if [ $? -ne ${FLAGS_TRUE} ]; then
      # TODO(kward): actually output the failed value
      _flags_warn 'getopt on this platform supports only short flags.'
      flags_error='unable to parse provided options with getopt.'
      flags_return=${FLAGS_ERROR}
    fi
  fi

  unset _flags_match_ _flags_opt_ _flags_shortOpts_
  return ${flags_return}
}

# Parse command-line options using the enhanced getopt.
#
# Note: the flag options are passed around in the global __flags_opts so that
# the formatting is not lost due to shell parsing and such.
#
# Args:
#   @: varies: command-line options to parse
# Returns:
#   integer: a FLAGS success condition
_flags_enhancedGetopt()
{
  flags_return=${FLAGS_TRUE}
  _flags_shortOpts_=`_flags_genOptStr ${__FLAGS_OPTSTR_SHORT}`
  _flags_boolOpts_=`echo "${__flags_boolNames}" \
    |sed 's/^ *//;s/ *$//;s/ /,/g'`
  _flags_longOpts_=`_flags_genOptStr ${__FLAGS_OPTSTR_LONG}`

  __flags_opts=`getopt \
      -o ${_flags_shortOpts_} \
      -l "${_flags_longOpts_},${_flags_boolOpts_}" \
      -- "$@" 2>&1`
  if [ $? -ne ${FLAGS_TRUE} ]; then
    # TODO(kward): actually output the failed value
    flags_error='unable to parse provided options with getopt.'
    flags_return=${FLAGS_ERROR}
  fi

  unset _flags_boolOpts_ _flags_longOpts_ _flags_shortOpts_
  return ${flags_return}
}

# Dynamically parse a getopt result and set appropriate variables.
#
# This function does the actual conversion of getopt output and runs it through
# the standard case structure for parsing. The case structure is actually quite
# dynamic to support any number of flags.
#
# Args:
#   @: varies: output from getopt parsing
# Returns:
#   integer: a FLAGS success condition
_flags_parseGetopt()
{
  FLAGS_ARGC=0
  flags_return=${FLAGS_TRUE}

  if [ ${__FLAGS_GETOPT_VERS} -ne ${__FLAGS_GETOPT_VERS_ENH} ]; then
    set -- $@
  else
    # note the quotes around the `$@' -- they are essential!
    eval set -- "$@"
  fi

  # handle options. note options with values must do an additional shift
  while true; do
    _flags_opt_=$1
    _flags_arg_=${2:-}
    _flags_type_=${__FLAGS_TYPE_NONE}

    # determine long flag name
    case "${_flags_opt_}" in
      --) shift; break ;;  # discontinue option parsing

      --*)  # long option
        _flags_opt_=`expr "${_flags_opt_}" : '--\(.*\)'`
        _flags_len_=${__FLAGS_LEN_LONG}
        if _flags_itemInList "${_flags_opt_}" ${__flags_longNames}; then
          _flags_name_=${_flags_opt_}
        else
          # check for negated long boolean version
          if _flags_itemInList "${_flags_opt_}" ${__flags_boolNames}; then
            _flags_name_=`expr "${_flags_opt_}" : 'no\(.*\)'`
            _flags_type_=${__FLAGS_TYPE_BOOLEAN}
            _flags_arg_=${__FLAGS_NULL}
          fi
        fi
        ;;

      -*)  # short option
        _flags_opt_=`expr "${_flags_opt_}" : '-\(.*\)'`
        _flags_len_=${__FLAGS_LEN_SHORT}
        if _flags_itemInList "${_flags_opt_}" ${__flags_shortNames}; then
          # yes. match short name to long name. note purposeful off-by-one
          # (too high) with awk calculations.
          _flags_pos_=`echo "${__flags_shortNames}" \
              |awk 'BEGIN{RS=" ";rn=0}$0==e{rn=NR}END{print rn}' \
                  e=${_flags_opt_}`
          _flags_name_=`echo "${__flags_longNames}" \
              |awk 'BEGIN{RS=" "}rn==NR{print $0}' rn="${_flags_pos_}"`
        fi
        ;;
    esac

    # die if the flag was unrecognized
    if [ -z "${_flags_name_}" ]; then
      flags_error="unrecognized option (${_flags_opt_})"
      flags_return=${FLAGS_ERROR}
      break
    fi

    # set new flag value
    [ ${_flags_type_} -eq ${__FLAGS_TYPE_NONE} ] && \
      _flags_type_=`_flags_getFlagInfo \
          "${_flags_name_}" ${__FLAGS_INFO_TYPE_STR}`
    case ${_flags_type_} in
      ${__FLAGS_TYPE_BOOLEAN})
        if [ ${_flags_len_} -eq ${__FLAGS_LEN_LONG} ]; then
          if [ "${_flags_arg_}" != "${__FLAGS_NULL}" ]; then
            eval "FLAGS_${_flags_name_}=${FLAGS_TRUE}"
          else
            eval "FLAGS_${_flags_name_}=${FLAGS_FALSE}"
          fi
        else
          _flags_strToEval_="_flags_val_=\
\${__flags_${_flags_name_}_${__FLAGS_INFO_DEFAULT_STR}}"
          eval "${_flags_strToEval_}"
          if [ ${_flags_val_} -eq ${FLAGS_FALSE} ]; then
            eval "FLAGS_${_flags_name_}=${FLAGS_TRUE}"
          else
            eval "FLAGS_${_flags_name_}=${FLAGS_FALSE}"
          fi
        fi
        ;;

      ${__FLAGS_TYPE_FLOAT})
        if _flags_validateFloat "${_flags_arg_}"; then
          eval "FLAGS_${_flags_name_}='${_flags_arg_}'"
        else
          flags_error="invalid float value (${_flags_arg_})"
          flags_return=${FLAGS_ERROR}
          break
        fi
        ;;

      ${__FLAGS_TYPE_INTEGER})
        if _flags_validateInteger "${_flags_arg_}"; then
          eval "FLAGS_${_flags_name_}='${_flags_arg_}'"
        else
          flags_error="invalid integer value (${_flags_arg_})"
          flags_return=${FLAGS_ERROR}
          break
        fi
        ;;

      ${__FLAGS_TYPE_STRING})
        eval "FLAGS_${_flags_name_}='${_flags_arg_}'"
        ;;
    esac

    # handle special case help flag
    if [ "${_flags_name_}" = 'help' ]; then
      if [ ${FLAGS_help} -eq ${FLAGS_TRUE} ]; then
        flags_help
        flags_error='help requested'
        flags_return=${FLAGS_FALSE}
        break
      fi
    fi

    # shift the option out
    shift
    FLAGS_ARGC=`expr ${FLAGS_ARGC} + 1`

    # additional shift for the argument
    if [ ${_flags_type_} != ${__FLAGS_TYPE_BOOLEAN} ]; then
      shift
      FLAGS_ARGC=`expr ${FLAGS_ARGC} + 1`
    fi
  done

  unset _flags_arg_ _flags_len_ _flags_name_ _flags_opt_ _flags_pos_ \
      _flags_strToEval_ _flags_type_ _flags_val_
  return ${flags_return}
}

#------------------------------------------------------------------------------
# public functions
#

# A basic boolean flag. Boolean flags do not take any arguments, and their
# value is either 1 (false) or 0 (true). For long flags, the false value is
# specified on the command line by prepending the word 'no'. With short flags,
# the presense of the flag toggles the current value between true and false.
# Specifying a short boolean flag twice on the command results in returning the
# value back to the default value.
#
# A default value is required for boolean flags.
#
# For example, lets say a Boolean flag was created whose long name was 'update'
# and whose short name was 'x', and the default value was 'false'. This flag
# could be explicitly set to 'true' with '--update' or by '-x', and it could be
# explicitly set to 'false' with '--noupdate'.
DEFINE_boolean() { _flags_define ${__FLAGS_TYPE_BOOLEAN} "$@"; }

# Other basic flags.
DEFINE_float()   { _flags_define ${__FLAGS_TYPE_FLOAT} "$@"; }
DEFINE_integer() { _flags_define ${__FLAGS_TYPE_INTEGER} "$@"; }
DEFINE_string()  { _flags_define ${__FLAGS_TYPE_STRING} "$@"; }

# Parse the flags.
#
# Args:
#   unnamed: list: command-line flags to parse
# Returns:
#   integer: success of operation, or error
FLAGS()
{
  # define a standard 'help' flag if one isn't already defined
  [ -z "${__flags_help_type:-}" ] && \
      DEFINE_boolean 'help' false 'show this help' 'h'

  # parse options
  # TODO(kward): look into '-T' option to test the internal getopt() version
  if [ ${__FLAGS_GETOPT_VERS} -ne ${__FLAGS_GETOPT_VERS_ENH} ]; then
    _flags_standardGetopt "$@"
  else
    _flags_enhancedGetopt "$@"
  fi
  flags_return=$?

  if [ ${flags_return} -eq ${FLAGS_TRUE} ]; then
    _flags_parseGetopt "${__flags_opts}"
    flags_return=$?
  fi

  [ ${flags_return} -eq ${FLAGS_ERROR} ] && _flags_fatal "${flags_error}"
  return ${flags_return}
}

# This is a helper function for determining the `getopt` version for platforms
# where the detection isn't working. It simply outputs debug information that
# can be included in a bug report.
#
# Args:
#   none
# Output:
#   debug info that can be included in a bug report
# Returns:
#   nothing
flags_getoptInfo()
{
  # platform info
  _flags_debug "uname -a: `uname -a`"
  _flags_debug "PATH: ${PATH}"

  # shell info
  if [ -n "${BASH_VERSION:-}" ]; then
    _flags_debug 'shell: bash'
    _flags_debug "BASH_VERSION: ${BASH_VERSION}"
  elif [ -n "${ZSH_VERSION:-}" ]; then
    _flags_debug 'shell: zsh'
    _flags_debug "ZSH_VERSION: ${ZSH_VERSION}"
  fi

  # getopt info
  getopt >/dev/null
  _flags_getoptReturn=$?
  _flags_debug "getopt return: ${_flags_getoptReturn}"
  _flags_debug "getopt --version: `getopt --version 2>&1`"

  unset _flags_getoptReturn
}

# Returns whether the detected getopt version is the enhanced version.
#
# Args:
#   none
# Output:
#   none
# Returns:
#   bool: true if getopt is the enhanced version
flags_getoptIsEnh()
{
  if [ ${__FLAGS_GETOPT_VERS} -eq ${__FLAGS_GETOPT_VERS_ENH} ]; then
    return ${FLAGS_TRUE}
  else
    return ${FLAGS_FALSE}
  fi
}

# Returns whether the detected getopt version is the standard version.
#
# Args:
#   none
# Returns:
#   bool: true if getopt is the standard version
flags_getoptIsStd()
{
  if [ ${__FLAGS_GETOPT_VERS} -eq ${__FLAGS_GETOPT_VERS_STD} ]; then
    return ${FLAGS_TRUE}
  else
    return ${FLAGS_FALSE}
  fi
}

# This is effectively a 'usage()' function. It prints usage information and
# exits the program with ${FLAGS_FALSE} if it is ever found in the command line
# arguments. Note this function can be overridden so other apps can define
# their own --help flag, replacing this one, if they want.
#
# Args:
#   none
# Returns:
#   integer: success of operation (always returns true)
flags_help()
{
  if [ -n "${FLAGS_HELP:-}" ]; then
    echo "${FLAGS_HELP}" >&2
  else
    echo "USAGE: ${FLAGS_PARENT:-$0} [flags] args" >&2
  fi
  if [ -n "${__flags_longNames}" ]; then
    echo 'flags:' >&2
    for _flags_name in ${__flags_longNames}; do
      _flags_flagStr=''

      _flags_default=`_flags_getFlagInfo \
          "${_flags_name}" ${__FLAGS_INFO_DEFAULT_STR}`
      _flags_help=`_flags_getFlagInfo \
          "${_flags_name}" ${__FLAGS_INFO_HELP_STR}`
      _flags_short=`_flags_getFlagInfo \
          "${_flags_name}" ${__FLAGS_INFO_SHORT_STR}`
      _flags_type=`_flags_getFlagInfo \
          "${_flags_name}" ${__FLAGS_INFO_TYPE_STR}`

      [ "${_flags_short}" != "${__FLAGS_NULL}" ] && \
          _flags_flagStr="${_flags_flagStr}-${_flags_short}"

      if [ ${__FLAGS_GETOPT_VERS} -eq ${__FLAGS_GETOPT_VERS_ENH} ]; then
        [ "${_flags_short}" != "${__FLAGS_NULL}" ] && \
            _flags_flagStr="${_flags_flagStr},"
        if [ ${_flags_type} -eq ${__FLAGS_TYPE_BOOLEAN} ]; then
          _flags_boolStr='[no]'
        else
          _flags_boolStr=''
        fi
        _flags_flagStr="${_flags_flagStr}--${_flags_boolStr}${_flags_name}:"
      fi

      case ${_flags_type} in
        ${__FLAGS_TYPE_BOOLEAN})
          if [ ${_flags_default} -eq ${FLAGS_TRUE} ]; then
            _flags_defaultStr='true'
          else
            _flags_defaultStr='false'
          fi
          ;;
        ${__FLAGS_TYPE_FLOAT}|${__FLAGS_TYPE_INTEGER})
          _flags_defaultStr=${_flags_default} ;;
        ${__FLAGS_TYPE_STRING}) _flags_defaultStr="'${_flags_default}'" ;;
      esac
      _flags_defaultStr="(default: ${_flags_defaultStr})"

      _flags_helpStr="  ${_flags_flagStr}  ${_flags_help} ${_flags_defaultStr}"
      _flags_helpStrLen=`expr "${_flags_helpStr}" : '.*'`
      flags_screenCols_=`_flags_screenColumns`
      if [ ${_flags_helpStrLen} -lt ${flags_screenCols_} ]; then
        echo "${_flags_helpStr}" >&2
      else
        _flags_emptyStr="`echo ${_flags_flagStr} |sed 's/./ /g'`"
        echo "  ${_flags_flagStr}  ${_flags_help}" >&2
        echo "  ${_flags_emptyStr}  ${_flags_defaultStr}" >&2
      fi
    done
  fi

  unset _flags_boolStr _flags_default _flags_defaultStr _flags_emptyStr \
      _flags_flagStr _flags_help _flags_helpStr _flags_helpStrLen _flags_name \
      _flags_short _flags_type
  return ${FLAGS_TRUE}
}

# Reset all flags back to their default values.
#
# Args:
#   none
# Returns:
#   nothing
flags_reset()
{
  for _flags_name in ${__flags_longNames}; do
    _flags_strToEval="unset FLAGS_${_flags_name}"
    for _flags_type in \
        ${__FLAGS_INFO_HELP_STR} \
        ${__FLAGS_INFO_SHORT_STR} \
        ${__FLAGS_INFO_TYPE_STR}
    do
      _flags_strToEval=\
"${_flags_strToEval} __flags_${_flags_name}_${_flags_type}"
    done
    eval ${_flags_strToEval}
  done

  # reset internal variables
  __flags_boolNames=' '
  __flags_longNames=' '
  __flags_shortNames=' '

  unset _flags_name _flags_type _flags_strToEval
}