#!/bin/sh


vo_sw_dir=${HOME}/vosw

error() {
    echo $@
    exit 1
}

log() {
    echo LOG: $@
}

get_write_lock() {
    log "Checking if the vo software area is writable."
    if [ -z $vo_sw_dir ] ; then
	error "\$$vo_sw_dir_var not set."
    fi

    if [ ! -w $vo_sw_dir ] ; then
	error "\$$vo_sw_dir_var ($vo_sw_dir) is not writable. (Check your proxy: are you the VO software manager?)" 
    fi
    log "$vo_sw_dir writable OK."
    # now do the lockfile shuffle
    lockfile=$vo_sw_dir/pkgsrc-lock
    log "checking lockfile $lockfile"
    if [ -f $lockfile ]; then
	log "lockfile exists."
	ls -l $lockfile
	if [ -z `find $lockfile -mmin -30` ]; then
	    log "stale lockfile ($lockfile is older than 30 minutes)"
	    rm -f $lockfile || error "could not remove $lockfile. Call help."
	else
	    log "lockfile is still fresh."
	    return 1
	fi
    else
	log "no lockfile found. Setting lock"
    fi
    # At this point, we've concluded we should try and set the lockfile.
    # be careful to avoid race conditions (although rare).
    log "attempting to get lock."
    a=`mktemp $vo_sw_dir/pkgsrc-lock.XXXXXXXXXX` || error "mktemp failed"
    ln $a $lockfile
    if [ $? -ne 0 ]; then
	log "failed to obtain lock"
	rm $a
	return 1
    fi
    log "lock set"
    rm $a
    unset a
    trap "rm -f $lockfile" INT TERM EXIT
    return 0
}

echo "try 1:"
get_write_lock
if [ $? -ne 0 ]; then
    echo fail
else
    echo ok
fi

echo "try 2:"
get_write_lock
if [ $? -ne 0 ]; then
    echo fail
else
    echo ok
fi