view mod_pubsub_subscription/README.markdown @ 5173:460f78654864

mod_muc_rtbl: also filter messages This was a bit tricky because we don't want to run the JIDs through SHA256 on each message. Took a while to come up with this simple plan of just caching the SHA256 of the JIDs on the occupants. This will leave some dirt in the occupants after unloading the module, but that should be ok; once they cycle the room, the hashes will be gone. This is direly needed, otherwise, there is a tight race between the moderation activities and the actors joining the room.
author Jonas Schäfer <jonas@wielicki.name>
date Tue, 21 Feb 2023 21:37:27 +0100
parents 97fac0ba0469
children
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# Introduction

This module lets you programmatically subscribe to updates from a
[pubsub][xep0060] node, even if the pubsub service is remote.

## Example

``` {.lua}
module:depends("pubsub_subscription");
module:add_item("pubsub-subscription", {
    service = "pubsub.example.com";
    node = "otter_facts";

    -- Callbacks:
    on_subscribed = function()
        module:log("info", "Otter facts incoming!");
    end;

    on_item = function(event)
        module:log("info", "Random Otter Fact: %s", event.payload:get_text());
    end;
});
```

## Usage

Ensure the module is loaded and add your subscription via the
`:add_item` API. The item table MUST have `service` and `node` fields
and SHOULD have one or more `on_<event>` callbacks.

The JID of the pubsub service is given in `service` (could also be the
JID of an user for advanced PEP usage) and the node is given in,
unsurprisingly, the `node` field.

The various `on_event` callback functions, if present, gets called when
new events are received. The most interesting would be `on_item`, which
receives incoming items. Available events are:

`on_subscribed`
:   The subscription was successful, events may follow.

`on_unsubscribed`
:   Subscription was removed successfully, this happens if the
    subscription is removed, which you would normally never do.

`on_error`
:   If there was an error subscribing to the pubsub service. Receives a
    table with `type`, `condition`, `text`, and `extra` fields as
    argument.

`on_item`
:   An item publication, the payload itself available in the `payload`
    field in the table provided as argument. The ID of the item can be
    found in `item.attr.id`.

`on_retract`
:   When an item gets retracted (removed by the publisher). The ID of
    the item can be found in `item.attr.id` of the table argument..

`on_purge`
:   All the items were removed by the publisher.

`on_delete`
:   The entire pubsub node was removed from the pubsub service. No
    subscription exists after this.

``` {.lua}
event_payload = {
    -- Common prosody event entries:
    stanza = util.stanza;
    origin = util.session;

    -- PubSub service details
    service = "pubsub.example.com";
    node = "otter_facts";

    -- The pubsub event itself
    item = util.stanza; -- <item/>
    payload = util.stanza; -- actual payload, child of <item/>
}
```

# Compatibility

Should work with Prosody \>= 0.11.x