#!/bin/bash

# Put this somewhere in your $PATH and execute w/o args once.
# For sps it may be convenient to run spa and spd in sudo w/o pwd.

p1=_sp_
p2=-

declare -A cmds

login_name() {
    local user=$1 session=$2
    echo "$p1$user$p2$session"
}

setup() {
    local dir=$(dirname $0) base=$(basename $0)
    for cmd in ${!cmds[*]}; do
        rm $dir/$cmd
        ln -sf $dir/$base $dir/$cmd
    done
    [ -x /usr/bin/screen ] && chmod +s /usr/bin/screen
    [ -d /var/run/screen ] && chmod 755 /var/run/screen
    exit 0
}

cmds[spc]=client
client() {
    [ ${#@} -eq 3 ] || {
        echo "usage: $0 <host> <user> <session>" 1>&2
        return 1
    }

    local host=$1 user=$2 session=$3
    local login=$(login_name $user $session)

    exec ssh $login@$host
}

cmds[sps]=server
server() {
    [ ${#@} -eq 1 ] || { echo "usage: $0 <session>"
        return 1
    }

    local user=$(id -un) session=$1
    local login=$(login_name $user $session)
    id $login &>/dev/null && {
        echo "session already exists" 1>&2
        return 2
    }

    sudo $(dirname $0)/spa $session
    screen -S $session -d -m bash -c "bash; sudo $(dirname $0)/spd $session"
    screen -S $session -X multiuser on
    screen -S $session -X aclchg $login -w '#'
    screen -S $session -X aclchg $login +x detach
    screen -S $session -X bindkey ^\\ detach
    screen -S $session -r
}

cmds[spa]=addlogin
addlogin() {
    [ ${#@} -eq 1 ] || return 1
    local user=$SUDO_USER session=$1
    local login=$(login_name $user $session)
    local path=$(readlink -m $0)
    useradd -d /tmp -M -s ${path%/*}/spsh $login
    echo -n "Password: "
    read -s pwd
    chpasswd <<END
$login:$pwd
END
}

cmds[spd]=dellogin
dellogin() {
    [ ${#@} -eq 1 ] || return 1
    local user=$SUDO_USER session=$1
    local login=$(login_name $user $session)
    userdel -f $login &>/dev/null
}

cmds[spsh]=shell
shell() {
    local login=$(id -un)
    local user=${login#$p1}

    user=${user%%$p2*}
    session=${login#*$p2}

    screen -x $user/$session
}

name=$(basename $0)
if [ ${cmds[$name]} ]; then
    ${cmds[$name]} $@
else
    setup
fi