#!/bin/sh

set -e

die() {
    echo >&2 "novaboot-shell: $*"
    exit 1
}

print_help() {
    cat <<EOF
Target commands:
- console
- reset
- on
- off
- rsync ...

Management commands:
- help
EOF

    if [ "$NB_ADMIN" ]; then
	cat <<EOF
- add-key
- shell (use with ssh -t)
EOF
    fi
    exit 0
}

add_key() {
    local user
    [ "$NB_ADMIN" ] || return 1

    case $# in
	0) die "Username argument missing";;
	1) break;;
	*) die "User name must not contain spaces: $*";;
    esac
    user="$1"
    key=$(cat)

    tmp=$(mktemp ~/.ssh/authorized_keys.XXXXXXXX)
    {
	cat ~/.ssh/authorized_keys
	echo "command=\"user $user\" $key"
    } | sort -u > $tmp

    mv $tmp ~/.ssh/authorized_keys
}

exec_shell() {
    [ "$NB_ADMIN" ] || die "Permission denied"
    exec /bin/bash || exec /bin/sh
}

lock_queue() {
    lslocks | awk '{ if ($9 == "'"$RUN_DIR"'") { print $2 } }'
}

print_queue() {
    local queue

    queue=$(
	for pid in $(lock_queue); do
	    echo $pid $(sed --null-data -ne '/^NOVABOOT_ID=/ s///p' /proc/$pid/environ)
	done | sort)
    if [ "$queue" ]; then
	echo "Target is occupied by:"
	( echo "PID USER LOGIN_TIME FROM"; echo "$queue" ) | column -t
    fi
}

locked() {
    print_queue
    tmp=$(mktemp)
    no_fork=
    flock -h 2>&1 | grep -q -e "--no-fork" && no_fork=--no-fork
    rm -f "$tmp"
    exec flock $no_fork "$RUN_DIR" "$@"
}

unlocked() {
    exec "$@"
}

check_var() {
    if eval [ "\"\$$1\"" ]; then
	return 0
    else
	die "$1 variable not defined in $CFG"
    fi
}

# run_subcommand should be called only after permission checks and/or locking
run_subcommand() {
    case "$*" in
	"console")
	    trap "rm -f $RUN_DIR/ppid" EXIT
	    echo $NOVABOOT_PPID > $RUN_DIR/ppid
	    echo 'novaboot-shell: Connected'
	    # TODO: $reset_begin_cmd
	    check_var console_cmd && eval exec $console_cmd;;
	"reset")
	    check_var reset_cmd && eval exec $reset_cmd;;
	"rsync --server "*" . .")
	    if ! [ $# -eq 5 -o \( $# -eq 6 -a "$4" = '--log-format=X' \) ]; then
		die "Unexpected rsync invocation: $*"
	    fi
	    mkdir -p "$HOME/tftproot"
	    cd "$HOME/tftproot"
	    exec "$@";;
	"on")
	    check_var on_cmd && eval exec $on_cmd;;
	"off")
	    check_var off_cmd && eval exec $off_cmd;;
    esac
}

main() {
    if [ "$1" = "-c" ]; then shift
    else die "Permission denied"; fi

    NB_ADMIN=
    if [ "${1%% *}" = "user" ]; then
	# Get user name encoded in ~/.ssh/authorized_keys
	set -- $1
	NB_USER="$2";
	[ "$3" = "admin" ] && NB_ADMIN=1
	set -- $SSH_ORIGINAL_COMMAND
    fi

    if [ $# -eq 0 ]; then print_help; fi

    IP=${SSH_CONNECTION%% *}
    HOST=$(getent hosts $IP) || HOST=$IP
    REMOTE=${HOST##* }
    DATE=$(LANG=C date +'%F_%T')
    export NOVABOOT_ID="${NB_USER:-?} $DATE ${REMOTE}"
    export NOVABOOT_PPID=$PPID

    mkdir -p "$RUN_DIR"

    case "$1" in
	# Commands allowed at any time
	"console") locked $0 console;;
	"get-config") target_config; exit;;
	"add-key") shift; add_key "$@"; exit;;
	"shell") exec_shell; exit;;
	"help") print_help;;

	# Commands allowed only when nobody or the same user is connected
	# to the console. "The same user" means that we were executed by
	# the same sshd process that has the lock. This is ensured by
	# using SSH connection sharing on cline side.
	reset | rsync | on | off)
	    ALLOWED_PPID=$(cat $RUN_DIR/ppid 2>/dev/null || :)
	    if [ "$PPID" -eq "${ALLOWED_PPID:-0}" ]; then run=unlocked; else run=locked; fi
	    $run $0 "$@";;
	*)
	    echo >&2 "novaboot-shell: Command not allowed: $*"
	    logger -p error "novaboot-shell: Command not allowed: $*"
	    exit 1;;
    esac
}

RUN_DIR="$HOME"

if [ "$NOVABOOT_SHELL_CONFIG" ]; then
    CFG="$NOVABOOT_SHELL_CONFIG"
else
    CFG="$HOME/.novaboot-shell"
fi

. "$CFG"

if [ -z "$NOVABOOT_ID" ]; then
    main "$@"
else
    run_subcommand "$@"
fi