#! /bin/bash

# Copyright (c) 2017 Agnibho Mondal
# All rights reserved
#
# This file is part of Equsol.
#
# Equsol 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 of the License, or (at your option) any later
# version.
#
# Equsol 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
# Equsol.  If not, see <http://www.gnu.org/licenses/>.
#
# Agnibho Mondal
# contact@agnibho.com
# www.agnibho.com

DIR="/home/agnibho/program/equsol/data/";

function calc {
	echo -e "\n$1\n";
	IFS="=" read LHS RHS <<< "$1";
	readarray -t VARS <<< "$(grep -oP "\[.*?\]" <<< "$RHS")";
	EQ=$RHS;
	for v in "${VARS[@]}"
	do
		read -p "$(echo "$v" | sed -E "s/\[|\]//g") = " val;
		if ! [[ $val =~ ^-?[0-9]+([.][0-9]+)?$ ]];then
			echo "Invalid input."
			exit 1;
		fi
		var=$(echo "$v" | sed -e 's/[]\/$*.^|[]/\\&/g');
		EQ="$(echo "$EQ" | sed "s/$var/$val/g")";
	done
	RES=$(echo "$EQ"|bc -l|sed "s/0*$//g"|sed "s/\.$//g"|sed "s/^\./0./g");
	echo -e "\n$(echo "$LHS" | sed -E "s/\[|\]|^ | $//g") = \033[1m$RES\033[0m";
}

if [ -f "$DIR$1" ];then
	EQS=();
	while read line;do
		if grep -q "^#" <<<"$line";then
			continue;
		elif grep -q "=" <<< "$line";then
			EQS+=("$line");
		fi
	done < "$DIR$1"
	if [ ${#EQS[@]} -gt 1 ];then
		for i in "${!EQS[@]}"
		do
			echo "($i) ${EQS[$i]}";
		done
		read -p "Enter equation number: " i;
		if ! [[ $i =~ ^[0-9]+$ ]];then
			echo "Invalid input.";
			exit 1;
		fi
		if [ -n "${EQS[$i]}" ];then
			calc "${EQS[$i]}";
		else
			echo "Invalid equation number.";
			exit 1;
		fi
	elif [ ${#EQS[@]} -eq 1 ];then
		calc "${EQS[0]}";
	else
		echo "No equation found";
		exit 1;
	fi
else
	echo "Available equations: ";
	ls "$DIR";
fi