#!/bin/sh -e
#
# 2019 Dennis Camera (dennis.camera at ssrq-sds-fds.ch)
#
# This file is part of cdist.
#
# cdist 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.
#
# cdist 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 cdist. If not, see <http://www.gnu.org/licenses/>.
#
#
# Check if the given editor is present on the target system and determine its
# absolute path.
#

die() {
	echo "$@" >&2
	exit 1
}

editor_missing() { die "Editor '$1' is missing on the target system."; }
editor_no_alternative() {
	die "Editor '$1' is not in the alternatives list of the target system." \
		"$(test -n "${editors}" && printf '\nPlease choose one of:\n\n%s\n' "${editors}")"
}

# No need to check for the path if the file is supposed to be removed.
test "$(cat "${__object}/parameter/state")" != 'absent' || exit 0


case $("${__explorer}/os")
in
	debian|devuan|ubuntu)
		has_alternatives=true

		# NOTE: Old versions do not support `--list`, in this case ignore the errors.
		#       This will require an absolute path to be provided, though.
		editors=$(update-alternatives --list editor 2>/dev/null)
		;;
	*)
		# NOTE: RedHat has an alternatives system but it doesn't usually track
		#       editors and it is a pain to extract the list.
		has_alternatives=false
		;;
esac

# Read --editor parameter and check its value since it is "optional"
editor=$(cat "${__object}/parameter/editor" 2>/dev/null) || true
test -n "${editor}" || die 'Please provide an --editor to configure.'

case $editor
in
	/*)
		is_abspath=true
		;;
	*/*)
		die 'Relative editor paths are not supported'
		;;
	*)
		is_abspath=false
		;;
esac


if $has_alternatives && test -n "${editors}"
then
	IFS='
'
	if ! $is_abspath
	then
		# First, try to resolve the absolute path using $editors.
		while true
		do
			for e in $editors
			do
				if test "$(basename "${e}")" = "${editor}"
				then
					editor="${e}"
					break 2  # break out of both loops
				fi
			done

			# Iterating through alternatives did not yield a result
			editor_no_alternative "${editor}"
			break
		done
	fi

	# Check if editor is present
	test -f "${editor}" || editor_missing "${editor}"

	for e in $editors
	do
		if test "${editor}" = "${e}"
		then
			# Editor is part of the alternatives list -> use it!
			echo "${editor}"
			exit 0
		fi
	done

	editor_no_alternative "${editor}"
else
	# NOTE: This branch is mostly for RedHat-based systems which do
	#       not track editor alternatives.  To make this type useful
	#       on RedHat at all we allow an absoloute path to be provided
	#       in any case.

	if $is_abspath
	then
		test -x "${editor}" || editor_missing "${editor}"

		echo "${editor}"
		exit 0
	else
		die "The target doesn't list any editor alternatives. " \
		    "Please specify an absolute path or populate the alternatives list."
	fi
fi

# The script should never reach this statement!
exit 1