#!/bin/bash

Myname="${0##*/}"
Version=1.02

:<<'DOC'
= texcalc - converts from one tex unit to another

= Synopsis
texcalc [options] [n.m]unit1 [unit2]	

texcalc 30bp pt		# → 30.11250pt
texcalc 30bp bp		# → 30.00000bp
texcalc 30bp mm		# → 10.58333mm
texcalc 10mm bp		# → 28.34645bp
texcalc 10mm cc		# → 2.21592cc
texcalc cc mm		# → 4.51278mm

== Options
-h,--help	print this help and exit
-H,--Help	print full documentation via less and exit
-V,--version	print version and exit
-s,--scale=X	set number of decimal places in the output to X
		Default: 5

= Description
texcalc converts [an amount of] TeX units to another TeX unit.
The default for the last is |pt|. Known units are:
  bp cc cm dd in mm pc pt

= Examples
These print 25.40000mm:

  texcalc in mm
  texcalc 1in mm
  texcalc 1.0in mm

The default output unit is pt, so this prints 1.00375pt:

  texcalc bp

= Author
[Wybo Dekker](wybodekker@me.com)

= Copyright
Released under the [GNU General Public License](www.gnu.org/copyleft/gpl.html)
DOC

REd='\e[38;5;9m' Nor='\e[0m'
    die() { local i; for i; do echo -e "$Myname: $REd$i$Nor"; done 1>&2; exit 1; }
helpsrt() { sed -n '/^= Synopsis/,/^= /p' "$0"|sed '1d;$d'; exit; }
helpall() { sed -n "/^:<<'DOC'$/,/^DOC/p" "$0"|sed '1d;$d'|
            less -P"$Myname-${Version/./·} (press h for help, q to quit)";exit; }

:<<'DOC' #----------------------------------------------------------------------
= handle_options
synopsis:	 handle_options "$@"
description:	handle the options.
globals used:	 Myname Version
globals  set:	 args
DOC
#-------------------------------------------------------------------------------
handle_options() {
   local options
   if ! options=$(getopt \
      -n "$Myname" \
      -o hHVIs: \
      -l help,Help,version,scale: -- "$@"
   ); then exit 1; fi
   eval set -- "$options"
   scale=5
   while [ $# -gt 0 ]; do
      case $1 in
      (-h|--help)    # print this help and exit
		     helpsrt
		     ;;
      (-H|--Help)    # print full documentation via less and exit
		     helpall
		     ;;
      (-V|--version) # print version and exit
		     echo $Version
		     exit
		     ;;
      (-s|--scale)   # set number of decimal places in the output to X
		     # Default: 5
		     scale=$2
		     shift 2;;
      (-I)	     instscript "$0" ||
   		        die 'the -I option is for developers only'
   		     exit
   		     ;;
      (--)           shift
		     break
		     ;;
      (*)	     break
		     ;;
      esac
   done
   args=( "$@" )
}

declare -A fac=(
  [bp]=' 7227.0 / 7200.0'
  [cc]='14856.0 / 1157.0'
  [cm]=' 7227.0 / 254.0 '
  [dd]=' 1238.0 / 1157.0'
  [in]=' 7227.0 / 100.0 '
  [mm]=' 7227.0 / 2540.0'
  [pc]=12
  [pt]=1
)

handle_options "$@"
set -- "${args[@]}"

[[ -z $1 ]] && helpsrt
inunit=${1//[[:digit:].]/}
inval=${1//[[:alpha:]]/}
[[ -z $inval ]] && inval=1
outunit=${2:-pt}
[[ -z ${fac[$inunit]} ]] &&
   die "first argument's unit ($inunit) unknown"
[[ -z ${fac[$outunit]} ]] &&
   die "second argument's unit ($outunit) unknown"
[[ $inval =~ ^[[:digit:]]+\.?([[:digit:]]+)?$ ]] ||
   die "invalid numerical value in first argument"
echo "$(echo "scale=$scale; $inval*(${fac[$inunit]})/(${fac[$outunit]})"|bc -l)$outunit"