# Copyright 1999-2009 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2
# $Id: $

DESCRIPTION="Manage /bin/sh (POSIX shell) implementations"
MAINTAINER="gentoo@mgorny.alt.pl"
VERSION="0.1"

# Based on work of Erik Hahn; bug #214817

## Functions ##

# find a list of sh symlink targets, best first
find_targets() {
	local t
	for t in \
			bash \
			dash \
			zsh \
			posh \
		; do
		if [[ -x "${ROOT}"/bin/${t} ]]; then
			echo ${t}
		fi
	done
}

# set the sh symlink
set_symlinks() {
	local target="${1}" targets

	[[ ! -L "${ROOT}"/bin/sh && -e "${ROOT}"/bin/sh ]] && \
		die -q "/bin/sh is not a symlink!"

	if is_number "${target}" && [[ ${target} -ge 1 ]]; then
		targets=( $(find_targets) )
		target=${targets[$(( ${target} - 1 ))]}
	fi

	if [[ -x "${ROOT}"/bin/${target} ]]; then
		local tmpf="${ROOT}"/bin/sh.new
		# we could use 'ln -f' to directly replace the symlink
		# but 'mv' is an atomic operation so it should be more fault-proof

		ln -s "${target}" "${tmpf}" || \
			die -q "Unable to create temporary symlink"
		if ! mv "${tmpf}" "${ROOT}"/bin/sh; then
			rm -f "${tmpf}" # cleanup
			die -q "Unable to replace /bin/sh symlink with ${target}"
		fi
	else
		die -q "Target '${target}' doesn't appear to be valid!"
	fi
}

### show action ###

describe_show() {
	echo "Show the current POSIX shell implementation"
}

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

	write_list_start "Current POSIX shell implementation:"
	if [[ -L "${ROOT}/bin/sh" ]]; then
		write_kv_list_entry "$(basename $(canonicalise ${ROOT}/bin/sh))" ""
	elif [[ -e "${ROOT}/bin/sh" ]]; then
		write_kv_list_entry "(not a symlink)" ""
	else
		write_kv_list_entry "(unset)" ""
	fi
}

### list action ###

describe_list() {
	echo "List available POSIX shell implementations"
}

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

	local i targets
	targets=( $(find_targets) )
	if [[ -n ${targets[@]} ]]; then
		for (( i = 0; i < ${#targets[@]}; i++ )) ; do
			[[ ${targets[${i}]} == $(basename $(canonicalise ${ROOT}/bin/sh)) ]] && \
				targets[${i}]="${targets[${i}]} $(highlight '*')"
		done
		write_list_start "Available POSIX shell implementations:"
		write_numbered_list "${targets[@]}"
	else
		write_kv_list_entry "(none found)" ""
	fi
}

### set action ###

describe_set() {
	echo "Set a new POSIX shell implementation"
}

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

describe_set_parameters() {
	echo "<target>"
}

do_set() {
	if [[ -z "${1}" ]]; then
		die -q "Not enough parameters"
	elif [[ -n "${2}" ]]; then
		die -q "Too many parameters"
	else
		set_symlinks "${1}"
	fi
}

### update action ###

describe_update() {
	echo "Automatically update the POSIX shell implementation"
}

describe_update_options() {
	echo "--if-unset : Do not override existing implementation"
}

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

	[[ "${1}" == "--if-unset" && -L "${ROOT}"/bin/sh && -x "${ROOT}"/bin/sh ]] && \
		return

	set_symlinks 1
}

# vim: set syn=sh :