NIP-XX
======

Access Control Upgrade
----------------------

`draft` `optional`

This NIP defines how to upgrade a public event with the property of limiting access to itself.

## Upgrading a Public Event

A public event (with no access control), such as of `kind:1`,
must be published or updated with a `full_event` tag pointing to a
`kind:40042` event address.

It may include one of the following tags holding a preview of the full event content:
`summary`, `image`, `audio`, `video`. The first holds a text excerpt while the others an URL.

Example:

```json
{
  "kind": 1063,
  "tags": [
    ["full_event", "40042:<32-bytes lowercase hex of a pubkey>:abc", "<recommended relay URL, optional>"],
    ["image", "<string with preview URI>"],
    ["dim", "800x600"]
  ],
  "content": "",
  ...
}
```

## Full Event

A "Full Event" is of `kind:40042`. It has [NIP-42](42.md) `A` tags the author
can update at will with the pubkeys allowed to access it.

It uses the custom NIP-42 event serialization for events that require `AUTH`.

The `.content` and other tags aren't fixed. The structure depends on the
kind of the public event it is protecting. For example, if it is
protecting a `kind:30023` event, it should have the structure defined on [NIP-23](23.md).

Example:

```json
{
  "kind": 40042,
  "pubkey": "<author_pubkey>",
  "tags": [
    ["d", "<random>"],
    ["A", "<author_pubkey>"], // important to keep author access right
    ["A", "<buyer_1_pubkey>"],
    ["A", "<buyer_2_pubkey>"],
    ["url", "https://some.place/file.webp"],
    ["dim", "800x600"]
  ],
  "content": "Happy New Year, my dear supporters!!",
  ...
}
```

## Requesting the Event

The client is expected to initially request the public event. For example, a microblogging client
will request `kind:1` events as usual.

If one of these events includes a `full_event` tag,
the client should request it with a filter that includes
a `#A` filter key set to the client's user pubkey.

If the user has rights to access the full event, the relay will send it
after the NIP-42 authentication flow.

For example: `{ kinds: [40042], authors: ["abc"], #d: ["xyz"], #A: ["<client's user pubkey>"], limit: 1 }`