# Functions for managing prokit sessions
#
# Copyright (C) 2014  Patrick McDermott
#
# This file is part of the ProteanOS Development Kit.
#
# The ProteanOS Development Kit 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.
#
# The ProteanOS Development Kit 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 the ProteanOS Development Kit.  If not, see
# <http://www.gnu.org/licenses/>.

session_id=
session_root=
session_arch=
session_plat=
session_mountdir=
session_sigs=
_session_es=

_session_mount()
{
	local fs=
	local dir=
	local fstype=
	local options=

	while read fs dir fstype options; do
		[ "x${dir}" = 'x' ] && continue
		mount -t "${fstype}" -o "${options}" -- "${fs}" \
			"${session_root}/${dir}"
	done <<-EOF
		$(profile_get_fstab "${session_arch}" "${session_plat}")
		EOF
}

_session_umount()
{
	local fs=
	local dir=
	local fstype=
	local options=

	while read fs dir fstype options; do
		[ "x${dir}" = 'x' ] && continue
		# umount sometimes complains that the /dev file system is busy.
		# Here's a kludge to try to handle that.  We better make sure
		# bind mounts get unmounted; otherwise, `rm -Rf ${root}` can be
		# painful.
		while ! umount -- "${session_root}/${dir}"; do
			sleep 1
		done
	done <<-EOF
		$(profile_get_fstab "${session_arch}" "${session_plat}" | \
			sed -n '1!G;h;$p')
		EOF
}

session_end()
{
	trap : ${session_sigs}

	# Unregister the session.
	profile_bind_umount "${session_arch}" "${session_plat}" \
		"${session_mountdir}" \
		"${session_root}/prokit/sessions/${session_id}/wd"
	rmdir -- "${session_root}/prokit/sessions/${session_id}/wd"
	rmdir -- "${session_root}/prokit/sessions/${session_id}"

	if ! mutex_is_unlockable "${session_root}/prokit/sessions.lock"; then
		if ! mutex_timedlock "${session_root}/prokit/sessions.lock" 5
		then
			error "$(get_msg 'cant_lock_sessions')"
			trap - ${session_sigs}
			return 1
		fi
	fi

	# Clear the sessions pool.  If there are no more sessions, unmount the
	# file systems.
	if rmdir -- "${session_root}/prokit/sessions" 2>/dev/null; then
		_session_umount
	fi

	mutex_unlock "${session_root}/prokit/sessions.lock"
	
	trap - ${session_sigs}

	return 0
}

_session_handle_sig()
{
	local sig="${1}"
	shift 1

	_session_es=$((128 + ${sig}))
}

_session_set_sigs()
{
	local i=
	local sig=

	# We need the signal *number* in the signal handler.  The only portable
	# and easy way to get the number of a named signal is to search for it
	# as in the following loop hack.
	i=0
	session_sigs=''
	while [ ${i} -lt 127 ]; do
		i=$((${i} + 1))
		sig="$(kill -l ${i} 2>/dev/null)" || continue
		case "${sig}" in
			'HUP' | 'INT' | 'QUIT' | 'ABRT' | 'ALRM' | 'TERM')
				session_sigs="${session_sigs} ${i}"
				trap "_session_handle_sig ${i}" ${i}
				;;
		esac
	done
}

session_begin()
{
	local root="${1}"
	local mountdir="${2}"
	local atexit="${3}"
	local installing="${4}"
	shift 4

	rand
	session_id=${rand_x}
	session_root="${root}"
	session_arch="$(cat -- "${root}/etc/proteanos_arch")"
	session_plat="$(cat -- "${root}/etc/proteanos_plat")"
	session_mountdir="${mountdir}"

	[ -d "${session_root}/prokit" ] || mkdir -- "${session_root}/prokit"
	if [ -f "${session_root}/prokit/installing" ] && ! ${installing}; then
		error "$(get_msg 'install_running')"
		return 1
	fi

	_session_set_sigs

	if ! mutex_timedlock "${session_root}/prokit/sessions.lock" 5; then
		error "$(get_msg 'cant_lock_sessions')"
		trap - ${session_sigs}
		return 1
	fi

	# Check for a sessions pool.
	if [ -d "${session_root}/prokit/sessions" ]; then
		if ! profile_file_systems_mounted "${session_root}" \
				"${session_arch}" "${session_plat}"; then
			# If a sessions pool exists but the file systems aren't
			# mounted, clean up the old sessions and mount the file
			# systems.
			rmdir -- "${session_root}/prokit/sessions/"*
			_session_mount
		fi
	else
		# If the sessions pool doesn't exist, create it and mount the
		# file systems.
		mkdir -- "${session_root}/prokit/sessions"
		_session_mount
	fi

	# Register the session.
	mkdir -- "${session_root}/prokit/sessions/${session_id}"
	mkdir -- "${session_root}/prokit/sessions/${session_id}/wd"
	profile_bind_mount "${session_arch}" "${session_plat}" \
		"${session_mountdir}" \
		"${session_root}/prokit/sessions/${session_id}/wd"

	mutex_unlock "${session_root}/prokit/sessions.lock"

	return 0
}

session_id()
{
	printf '%d\n' ${session_id}
	return 0
}

session_dir()
{
	printf '/prokit/sessions/%d\n' ${session_id}
	return 0
}

session_exec()
{
	local args=
	local session_dir=

	_session_es=0

	args=''
	for arg in "${@}"; do
		arg="'$(printf '%s\n' "${arg}" | sed "s/'/'\\\\''/g")'"
		args="${args} ${arg}"
	done
	session_dir="/prokit/sessions/${session_id}/wd"
	chroot "${session_root}" /bin/sh -c "cd ${session_dir}; ${args}" || \
		return ${?}

	return ${_session_es}
}