# -*-eselect-*-  vim: ft=eselect
# Copyright 1999-2018 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2

DESCRIPTION="Manage /usr/bin/unison versions"
MAINTAINER="ml@gentoo.org"
VERSION="0.4"

# find a list of unison symlink targets, best first
find_targets() {
	local f
	for f in "${EROOT}"/usr/bin/unison-[0-9]*; do
		if [[ -f ${f} ]] ; then
			echo "${f##*/unison-}"
		fi
	done | tac
}

# find version number of currently symlinked version
identify_target() {
	local f
	f="$(canonicalise "${EROOT}"/usr/bin/unison)"
	echo "${f##*/unison-}"
}

function is_link_or_empty() {
    if [[ ! -e "$1" ]] || [[ -L "$1" ]]; then
		return 0
	else
		return 1
	fi
}
    
# set the unison symlink
set_symlinks() {
	local target="${1}" targets
	if is_number "${target}" && [[ ${target} -ge 1 ]] ; then
		targets=( $(find_targets) )
		target=${targets[target - 1]}
	fi
	if [[ -f "${EROOT}/usr/bin/unison-${target}" ]] ; then
		ln -sf "unison-${target}" "${EROOT}/usr/bin/unison" || \
			die "Could not set ${target} /usr/bin/unison symlink"
	else
		die -q "Target \"${target}\" doesn't appear to be valid!"
	fi
	# If unison-fsmonitor isn't a symlink, it means that we still have a
	# unison version (<2.48-r1) that doesn't properly slot that binary.
	# Don't mess with it if that's the case.
	if is_link_or_empty "${EROOT}/usr/bin/unison-fsmonitor" ; then
		# not a regular file. safe to symlink.
		ln -sf "unison-fsmonitor-${target}" \
			"${EROOT}/usr/bin/unison-fsmonitor" \
			|| die "Could not set ${target} /usr/bin/unison-fsmonitor symlink"
	fi
}

### show action ###

describe_show() {
	echo "Show the current unison version"
}

do_show() {
	[[ -z "${@}" ]] || die -q "Too many parameters"

	write_list_start "Current unison version:"
	if [[ -L "${EROOT}/usr/bin/unison" ]] ; then
		write_kv_list_entry "$(identify_target)" ""
	elif [[ -e "${EROOT}/usr/bin/unison" ]] ; then
		write_kv_list_entry "(not a symlink)" ""
	else
		write_kv_list_entry "(unset)" ""
	fi
}

### list action ###

describe_list() {
	echo "List available unison versions"
}

do_list() {
	[[ $# -eq 0 ]] || die -q "Too many parameters"

	local i targets current
	targets=( $(find_targets ) )
	current=$(identify_target)
	for (( i = 0; i < ${#targets[@]}; i++ )); do
		[[ ${targets[i]} = ${current} ]] \
			&& targets[i]=$(highlight_marker "${targets[i]}")
	done
	write_list_start "Available unison versions:"
	write_numbered_list -m "(none found)" "${targets[@]}"
}

### set action ###

describe_set() {
	echo "Set a new unison version"
}

describe_set_options() {
	echo "target : Target version number or index from 'list' action"
}

describe_set_parameters() {
	echo "<target>"
}

do_set() {
	if [[ -z "${1}" ]] ; then
		die -q "You didn't give me a version number"

	elif [[ -n "${2}" ]] ; then
		die -q "Too many parameters"

	elif [[ -L "${EROOT}/usr/bin/unison" ]] ; then
		if ! set_symlinks "${1}" ; then
			die -q "Can't set new version"
		fi

	elif [[ -e "${EROOT}/usr/bin/unison" ]] ; then
		die -q "${EROOT}/usr/bin/unison seems to be from an old ebuild, please remove manually"

	else
		set_symlinks "${1}" || die -q "Can't set new version"
	fi
}

### update action ###

describe_update() {
	echo "Automatically update the unison version number"
}

describe_update_options() {
	echo "--if-unset : Do not override currently selected version"
}

do_update() {
	[[ -z "${1}" ]] || ( [[ -z "${2}" ]] && [[ "${1}" == "--if-unset" ]] ) || \
		die -q "Usage error"

	if [[ -L "${EROOT}/usr/bin/unison" ]] && [[ ${1} == "--if-unset" ]]; then
		return
	fi
	if ! is_link_or_empty "${EROOT}/usr/bin/unison" ; then
		die -q "${EROOT}/usr/bin/unison seems to be from an old ebuild, please remove manually"
	elif [[ -z $(find_targets ) ]] ; then
		rm -f "${EROOT}/usr/bin/unison"
		rm -f "${EROOT}/usr/bin/unison-fsmonitor"
	else
		set_symlinks 1 || die -q "Can't set a new version"
	fi
}