#!/bin/sh
set -eu

usage() {
    printf '%s\n' "usage: left4me-journalctl <server-name> --lines <n> --follow|--no-follow" >&2
    exit 2
}

validate_name() {
    name=$1
    [ -n "$name" ] || usage
    case "$name" in
        .*|*..*|*/*|*\\*) usage ;;
    esac
    case "$name" in
        *[!A-Za-z0-9_.-]*) usage ;;
    esac
}

[ "$#" -eq 4 ] || usage
name=$1
lines_flag=$2
lines=$3
follow_flag=$4

validate_name "$name"
[ "$lines_flag" = "--lines" ] || usage
case "$lines" in
    ''|*[!0-9]*) usage ;;
esac

follow_arg=
case "$follow_flag" in
    --follow) follow_arg=-f ;;
    --no-follow) ;;
    *) usage ;;
esac

unit="left4me-server@${name}.service"
if [ -x /bin/journalctl ]; then
    journalctl=/bin/journalctl
elif [ -x /usr/bin/journalctl ]; then
    journalctl=/usr/bin/journalctl
else
    printf '%s\n' 'journalctl not found at /bin/journalctl or /usr/bin/journalctl' >&2
    exit 69
fi

if [ -n "$follow_arg" ]; then
    exec "$journalctl" -u "$unit" -n "$lines" -o cat "$follow_arg"
fi

exec "$journalctl" -u "$unit" -n "$lines" -o cat