#!/usr/bin/env bash

#############################################################################
## 
##   Logtalk backend Prolog compiler select script
##   Last updated on May 17, 2018
## 
##   This file is part of Logtalk <https://logtalk.org/>  
##   Copyright 1998-2020 Paulo Moura <pmoura@logtalk.org>
##   
##   Licensed under the Apache License, Version 2.0 (the "License");
##   you may not use this file except in compliance with the License.
##   You may obtain a copy of the License at
##   
##       http://www.apache.org/licenses/LICENSE-2.0
##   
##   Unless required by applicable law or agreed to in writing, software
##   distributed under the License is distributed on an "AS IS" BASIS,
##   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
##   See the License for the specific language governing permissions and
##   limitations under the License.
## 
#############################################################################


print_version() {
	echo "Current $(basename "$0") version:"
	echo "  0.8"
	exit 0
}


list_backends() {
	echo "Available backend Prolog compilers:"
	if [ -e "$(command -v bplgt)" ] && [ "$(command -v bp)" != "" ] ; then
		echo -n "  bplgt"
	fi
	if [ -e "$(command -v cxlgt)" ] && [ "$(command -v cxprolog)" != "" ] ; then
		echo -n "  cxlgt"
	fi
	if [ -e "$(command -v eclipselgt)" ] && [ "$(command -v eclipse)" != "" ] ; then
		echo -n "  eclipselgt"
	fi
	if [ -e "$(command -v gplgt)" ] && [ "$(command -v gprolog)" != "" ] ; then
		echo -n "  gplgt"
	fi
	if [ -e "$(command -v jiplgt)" ] && [ "$(command -v jipconsole.sh)" != "" ] ; then
		echo -n "  jiplgt"
	fi
	if [ -e "$(command -v lplgt)" ] && [ "$(command -v lprolog)" != "" ] ; then
		echo -n "  lplgt"
	fi
	if [ -e "$(command -v qplgt)" ] && [ "$(command -v qp)" != "" ] ; then
		echo -n "  qplgt"
	fi
	if [ -e "$(command -v sicstuslgt)" ] && [ "$(command -v sicstus)" != "" ] ; then
		echo -n "  sicstuslgt"
	fi
	if [ -e "$(command -v swilgt)" ] && [ "$(command -v swipl)" != "" ] ; then
		echo -n "  swilgt"
	fi
	if [ -e "$(command -v xsblgt)" ] && [ "$(command -v xsb)" != "" ] ; then
		echo -n "  xsblgt"
	fi
	if [ -e "$(command -v xsbmtlgt)" ] && [ "$(command -v xsb-mt)" != "" ] ; then
		echo -n "  xsbmtlgt"
	fi
	if [ -e "$(command -v yaplgt)" ] && [ "$(command -v yap)" != "" ] ; then
		echo -n "  yaplgt"
	fi
	echo
	exit 0
}


show_selected() {
	echo "Current Prolog integration script:"
	if [ -e "$(command -v logtalk)" ] && [ "$(command -v logtalk)" != "" ] ; then
		echo -n "  "
		readlink "$(command -v logtalk)"
	else
		echo "  none"
	fi
	exit 0
}


remove_link() {
	if [ -e "$(command -v logtalk)" ] && [ "$(command -v logtalk)" != "" ] ; then
		if rm "$(command -v logtalk)" ; then
			echo "Symbolic link removed"
		else
			echo "An error occurred while trying to remove the symbolic link!" >&2
			echo "Check that you are executing this script with the necessary permissions." >&2
			exit 1
		fi
	else
		echo "Symbolic link not defined"
	fi
	exit 0
}


usage_help() {
	echo 
	echo "This script allows the definition of a default backend Prolog compiler by"
	echo "creating a symbolic link, \"logtalk\", to the corresponding integration script."
	echo
	echo "Usage:"
	echo "  $(basename "$0") integration-script"
	echo "  $(basename "$0") -v"
	echo "  $(basename "$0") -l"
	echo "  $(basename "$0") -s"
	echo "  $(basename "$0") -r"
	echo "  $(basename "$0") -h"
	echo
	echo "Optional arguments:"
	echo "  -v print script version"
	echo "  -l list available Prolog integration scripts"
	echo "  -s show the currently selected Prolog integration script"
	echo "  -r remove the \"logtalk\" symbolic link"
	echo "  -h help"
	echo
}


valid_backend() {
	if [ "$1" == "bplgt" ] && [ -e "$(command -v bplgt)" ]  && [ "$(command -v bp)" != "" ] ; then
		return 0
	elif [ "$1" == "cxlgt" ] && [ -e "$(command -v cxlgt)" ]  && [ "$(command -v cxprolog)" != "" ] ; then
		return 0
	elif [ "$1" == "eclipselgt" ] && [ -e "$(command -v eclipselgt)" ]  && [ "$(command -v eclipse)" != "" ] ; then
		return 0
	elif [ "$1" == "gplgt" ] && [ -e "$(command -v gplgt)" ]  && [ "$(command -v gprolog)" != "" ] ; then
		return 0
	elif [ "$1" == "jiplgt" ] && [ -e "$(command -v jiplgt)" ]  && [ "$(command -v jipconsole.sh)" != "" ] ; then
		return 0
	elif [ "$1" == "lplgt" ] && [ -e "$(command -v lplgt)" ]  && [ "$(command -v lprolog)" != "" ] ; then
		return 0
	elif [ "$1" == "qplgt" ] && [ -e "$(command -v qplgt)" ]  && [ "$(command -v qp)" != "" ] ; then
		return 0
	elif [ "$1" == "sicstuslgt" ] && [ -e "$(command -v sicstuslgt)" ]  && [ "$(command -v sicstus)" != "" ] ; then
		return 0
	elif [ "$1" == "swilgt" ] && [ -e "$(command -v swilgt)" ]  && [ "$(command -v swipl)" != "" ] ; then
		return 0
	elif [ "$1" == "xsblgt" ] && [ -e "$(command -v xsblgt)" ]  && [ "$(command -v xsb)" != "" ] ; then
		return 0
	elif [ "$1" == "xsbmtlgt" ] && [ -e "$(command -v xsbmtlgt)" ]  && [ "$(command -v xsb-mt)" != "" ] ; then
		return 0
	elif [ "$1" == "yaplgt" ] && [ -e "$(command -v yaplgt)" ]  && [ "$(command -v yap)" != "" ] ; then
		return 0
	else
		return 1
	fi
}


switch_backend() {
	if valid_backend "$1" ; then
		cd "$(dirname "$(command -v "$1")")" || exit 1
		rm -f logtalk
		if ln -sf "$1" logtalk ; then
			echo "Switched to the Prolog integration script:"
			echo "  $1"
			exit 0
		else
			echo "An error occurred when switching the default Prolog integration script!" >&2
			echo "Check that you are executing this script with the necessary permissions." >&2
			exit 1
		fi
	else
		echo "Invalid Prolog integration script: $1" >&2
		exit 1
	fi
}


while getopts "vlsrh" option
do
	case $option in
		v) print_version;;
		l) list_backends;;
		s) show_selected;;
		r) remove_link;;
		h) usage_help; exit;;
		*) usage_help; exit;;
	esac
done


if [ "$1" == "" ]; then
	usage_help
	exit 0
else
	if switch_backend "$1" ; then
		exit 0
	else
		echo "An error occurred when switching to the $1 Prolog integration script!" >&2
		exit 1
	fi
fi
