#!/bin/sh

# calcpath return a path which is $1/$2/$3 when $2 is relative and $2/$3 if absolute.

# Copyright (C) 2021-2022 Free Software Foundation, Inc.
# Contributed by Gaius Mulley <gaius.mulley@southwales.ac.uk>.
#
# This file is part of GNU Modula-2.
#
# GNU Modula-2 is free software; you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free
# Software Foundation; either version 3, or (at your option) any later
# version.
#
# GNU Modula-2 is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
# for more details.
#
# You should have received a copy of the GNU General Public License along
# with gm2; see the file COPYING.  If not, write to the Free Software
# Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. *)


Usage () {
   echo "Usage: calcpath pathcomponent1 pathcomponent2 subdir"
   echo -n "  if pathcomponent1 is relative then pathcomponent1/pathcomponet2/subdir is"
   echo " returned"
   echo "  otherwise pathcomponet2/subdir is returned"
   echo "  the path is checked for legality in subdir."
}


if [ $# -eq 3 ]; then
   if [ "$(echo $2 | cut -b 1)" = "." ] ; then
       # relative path
       the_path=$1/$2/$3
   else
       the_path=$2/$3
   fi
   cd $3
   if realpath ${the_path} > /dev/null ; then
       echo ${the_path}
   else
       echo "calcpath: error ${the_path} is not a valid path in subdirectory $3" 1>&2
       exit 1
   fi
else
   Usage
   exit 1
fi