Event (based) Routing Module

...
$avp(filter) = "aor=*@opensips.org"
notify_on_event("E_UL_AOR_INSERT","$avp(filter)","reg_done","60");
...
route[reg_done] {
	xlog("a new user $avp(aor) registered with opensips.org domain\n");
}

...
# wait for callee to register
$avp(filter) = "aor="+$rU+"@"+$rd
async( wait_for_event("E_UL_AOR_INSERT","$avp(filter)", "40"),  resume_call);
# done
...
route[resume_call] {
	xlog("user $avp(aor) is now registered\n");
	lookup("location");
	t_relay();
}

...
route[route_to_user] {

    # prepare transaction for branch injection; it is mandatory
    # to create the transaction before the subscription, otherwise
    # the EBR module will not pass the transaction ID into the
    # notification route
    t_newtran();

    # keep the transaction alive (even if all branches will 
    # terminate) until the FR INVITE timer hits (we want to wait
    # for new possible contacts being registered)
    t_wait_for_new_branches();

    # subscribe to new contact registration event,
    # but for our callee only
    $avp(filter) = "aor="+$rU;
    notify_on_event("E_UL_CONTACT_INSERT","$avp(filter)",
        "fork_call", "20");

    # fetch already registered contacts and relay if any
    if (lookup("location"))
        route(relay);
    # if there were no contacts available (so no branches 
    # created so far), the created transaction will still be 
    # waiting for new branches due to the usage of the 
    # t_wait_for_new_branches() function

    exit;
}

route[fork_call]
{
    xlog("user $avp(aor) registered the a new "
        "contact $avp(uri), injecting\n");
    # take the contact described by the E_UL_CONTACT_INSERT
    # event and inject it as a new branch into the original
    # transaction
    t_inject_branches("event");
}
...

...
route[handle_call]
    if ($rU=="33") {
        ## this is a call to the pickup service
        ## (Charlie calling 33)

        # reject incoming call as we will generate an back call
        # from the original call (Alice to Bob)
        t_newtran();
        send_reply("480","Gone");

        # raise the pickup custom event
        # with pickup group 1 and picker being Charlie (caller)
        $avp(attr-name) = "group";
        $avp(attr-val) = "1";
        $avp(attr-name) = "picker";
        $avp(attr-val) = $fu;
        raise_event("E_CALL_PICKUP", $avp(attr-name), $avp(attr-val));

        exit;
    } else {

        ## this is a call to a subscriber
        ## (Alice calls Bob)

        # apply user location
        if (!lookup("location","m")) {
            send_reply("404", "Not Found");
            exit;
        }

        # prepare transaction for branch injection; it is mandatory
        # to create the transaction before the subscription, otherwise
        # the EBR module will not pass the transaction ID into the
        # notification route
        t_newtran();

        # subscribe to a call pickup event, but for our group only
        $avp(filter) = "group=1";
        notify_on_event("E_CALL_PICKUP","$avp(filter)",
            "handle_pickup", "20");

        t_relay();
    }
    exit;
}

route[handle_pickup]
{
    xlog("call picked by $avp(picker), fetching its contacts\n");
    if (lookup("location","", "$avp(picker)")) {
        # take the contacts retured by lookup() (for Charlie)
        # and inject them into the original call, but also cancel
        # any existing ongoing branch (ringing to Bob)
        t_inject_branches("msg","cancel");
    }
}