#!/bin/sh
#-
# Copyright (c) 2020 Daniel Morante
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#
#

set -e

progname=${0##*/}

#
# Print an error message and exit.
#
error() {
	echo "$progname: $*" >&2
	exit 1
}

#
# Print a usage string and exit.
#
usage() {
	echo "usage: $progname [-hbfo]" >&2
	exit 1
}

#
# Main program.
#
main () {
	while getopts :f:s: flag; do
		case "$flag" in
		f) ini_config=$OPTARG ;;
		s) ini_section=$OPTARG ;;
		\?) echo "Invalid option: -$OPTARG" >&2; return 1 ;;
		:) echo "Option -$OPTARG requires an argument." >&2; return 1 ;;
		esac
	done
	shift $(($OPTIND-1))

	ini_value=$1
	ini_directive=`echo $ini_value | cut -d'=' -f1`

	if [ -z "$ini_value" ] || [ -z "$ini_section" ] || [ -z "$ini_directive" ] || [ -z "$ini_config" ]; then	echo -e \\n"Mssing arguments"; return 1; fi

	# Keep track of the end of file line
	last_line=$(awk 'END {print NR}' $ini_config)

	# Find out what line the section begins
	starting_line=$(awk "/\[${ini_section}\]/ {print FNR}" $ini_config)

	# If the section does not exists
	if [ -z "$starting_line" ]; then
		# Add this section
		starting_line=$last_line
		echo -e "[${ini_section}]" >> $ini_config;
	fi

	# Find out what line the section ends
	next_section=$(awk "NR>${starting_line}&&/\[.*\]/ {print FNR}" $ini_config)
	if [ -z "$next_section" ]; then 
		ending_line=$last_line
	else
		ending_line=$(($next_section - 1))
	fi

	# Make the change within the disired range
	# Search starts right after the section header, not including it.
	starting_line=$(($starting_line + 1))
	if awk "NR==${starting_line},NR==${ending_line}" $ini_config | grep -sq $ini_directive >&2; then
		sed -i '' -e "${starting_line},${ending_line}s#$ini_directive.*#$ini_value#" $ini_config
	else
		insert_line=$ending_line
		# If we are at EOF, add a new line
		if [ $insert_line == $last_line ]; then echo >> $ini_config; fi
		before_line=$(( $ending_line - 1))
		before_line_value=$(awk "NR==${before_line}" $ini_config)
		if [ -z "$before_line_value" ]; then insert_line=$before_line; fi
		insert_line_value=$(awk "NR==${insert_line}" $ini_config)
		if [ ! -z "$insert_line_value" ]; then insert_line=$(($insert_line + 1)); fi
		#echo -e "${insert_line}\ni\n${ini_value}\n.\n\$\na\n\n.\n?^..*?+1,.d\nw\n" | ed -s $ini_config
		echo -e "${insert_line}\ni\n${ini_value}\n.\nw\n" | ed -s $ini_config
	fi
}

main "$@"