From 87ee7c20049113d5d010444abed236262afc2240 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Andr=C3=A9=20Menrath?= Date: Thu, 7 Mar 2024 15:49:06 +0100 Subject: [PATCH] wip documentation on how to write new event transformers --- transformer.md | 55 ++++++++++++++++++++++++++++++-------------------- 1 file changed, 33 insertions(+), 22 deletions(-) diff --git a/transformer.md b/transformer.md index 91e6540..ebb1779 100644 --- a/transformer.md +++ b/transformer.md @@ -1,17 +1,17 @@ -# Write a specialized ActivityPub transformer for an Event Custom Post Type +# Write a specialized ActivityPub transformer for an Event-Custom-Post-Type -> **_NOTE:_** This documentation is also likely to be userfu for other types other than events. +> **_NOTE:_** This documentation is also likely to be userful for content types other than events. -The ActivityPub plugin offers a basic support for all post types out of the box, but it also allows the registration of external transformers. A transformer is a class that implements the [abstract transformer class](https://github.com/Automattic/wordpress-activitypub/blob/fb0e23e8854d149fdedaca7a9ea856f5fd965ec9/includes/transformer/class-base.php) and is responsible for generating the ActivityPub JSON representation of an WordPress post or comment. +The ActivityPub plugin offers a basic support for all post types out of the box, but it also allows the registration of external transformers. A transformer is a class that implements the [abstract transformer class](https://github.com/Automattic/wordpress-activitypub/blob/fb0e23e8854d149fdedaca7a9ea856f5fd965ec9/includes/transformer/class-base.php) and is responsible for generating the ActivityPub JSON representation of an WordPress post or comment object. ## Hooks -To make the WordPress ActivityPub plugin use our custom transformer we simply add a filter to the `activitypub_transformer` hook which provides access to the transformer factory. The [transformer factory](https://github.com/Automattic/wordpress-activitypub/blob/master/includes/transformer/class-factory.php#L12) determines which transformer is used to transform a WordPress object to ActivityPub. +To make the WordPress ActivityPub plugin use a custom transformer simply add a filter to the `activitypub_transformer` hook which provides access to the transformer factory. The [transformer factory](https://github.com/Automattic/wordpress-activitypub/blob/master/includes/transformer/class-factory.php#L12) determines which transformer is used to transform a WordPress object to ActivityPub. ```php function register_custom_transformer_for_my_post_type( $transformer, $wp_object, $object_class ) { // Return a custom transformer, if the WordPress object is a post and the post type matches. - if ( 'WP_Post' === $object_class && $wp_object->post_type === 'my_event_post_type' ) { + if ( 'WP_Post' === $object_class && 'my_event_post_type' === $wp_object->post_type ) { require_once __DIR__ . '/includes/activitypub/transformer/class-my-custom-transformer.php'; return new My_Event_Post_Type_Transformer( $wp_object ); } @@ -26,11 +26,11 @@ add_filter( ) ``` -> **_NOTE:_** issues could arrise if this filter gets applied multiple times, be sure to take the priority argument of the `add_filter` into account. +> **_NOTE:_** issues could arrise if this filter gets applied multiple times, be sure to take the [priority argument](https://developer.wordpress.org/reference/functions/add_filter/#parameters) of the `add_filter` into account. ## Writing an event transformer class -If you are writing a transformer for your custom post type it is recommended to start by extending the upstream generic [post transformer](https://github.com/Automattic/wordpress-activitypub/blob/fb0e23e8854d149fdedaca7a9ea856f5fd965ec9/includes/transformer/class-post.php). It contains useful default implementations for generating the [attachments](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-attachment), rendering a proper [content](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-content) in HTML from either blocks or the classic editor, extracting [tags](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-tag) and more. +If you are writing a transformer for a custom post type it is recommended to start by extending the upstream generic [post transformer](https://github.com/Automattic/wordpress-activitypub/blob/fb0e23e8854d149fdedaca7a9ea856f5fd965ec9/includes/transformer/class-post.php). It contains useful default implementations for generating the [attachments](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-attachment), rendering a proper [content](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-content) in HTML from either blocks or the classic editor, extracting [tags](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-tag) and more. ```php /** @@ -39,7 +39,7 @@ If you are writing a transformer for your custom post type it is recommended to class My_Event_Post_Type_Transformer extends Activitypub\Transformer\Post; { ``` -The main function which controls the transformation is `to_object`. This one is called by the ActivityPub plugin to get the resulting ActivityPub representation as an PHP-array. The convertion to json takes place later and you don't need to cover that. +The main function which controls the transformation is `to_object`. This one is called by the ActivityPub plugin to get the resulting ActivityPub representation as an PHP-array. The convertion to JSON-LD takes place later and you don't need to cover that. ```php /** @@ -55,27 +55,38 @@ public function to_object() { } ``` +The ActivityPub object classes contain dynamic getter and setter functions: `set_` and `get_`. Of course, the property with `property-name` must exist for these to work. The function `transform_object_properties` tries to set all properties known to the ActivityPub object where a function called `get_` exists in the current transformer class. ### How to add new properties -### How to customize the JSON-LD context +Adding new properties is not encouraged to do at the transformer level. It's recommended to create a proper target ActivityPub object first. The target ActivityPub object also controls the the JSON-LD context via the constant `JSON_LD_CONTEXT`. [Example](https://github.com/Automattic/wordpress-activitypub/blob/fb0e23e8854d149fdedaca7a9ea856f5fd965ec9/includes/activity/extended-object/class-event.php#L21). +### Properties + +> **_NOTE:_** Within PHP all properties are snake_case, they will be transformed to the according CamelCase by the ActivityPub plugin. So if to you set `start_time` by using the ActivityPub objects class nfunction `set_start_time` or implementing a getter function in the transformer class called `get_start_time` the property `startTime` will be set accordingly in the JSON representation of the resulting ActivityPub object. + +You can find all available event related properties in the [event class](https://github.com/Automattic/wordpress-activitypub/blob/master/includes/activity/extended-object/class-event.php) along documentation and with links to the specifications. + +#### Mandatory Properties for an Event + +In order to ensure your events are comatible with other ActivityPub Event implementations there are several required properties that must be set by your transformer. + +* **[type](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-type)**: if using the `Activitypub\Activity\Extended_Object\Event` class the type will default to `Event` without doing anything. + +* **[startTime](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-startTime)**: the events start time + +* **[name](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-name)**: the title of the event + +#### Recommended properties for an Event in order to achieve good interoperability with other ActivityPub platforms + +* **[summary](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-summary)**: Other ActivityPub platforms that don't natively support event should use the summary (and the `name`) to display it as an converted object type. For example Mastodon converts an `Event` object to a `Note`. It is recommended to write the summary as text-centered with minimal HTML markup and that it contains the most important event details like place, time, etc. + +* **isOnline**: + +... -### Mandatory properties -#### type -```php - /** - * Returns the ActivityStreams 2.0 Object-Type for an Event. - * - * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-event - * @return string The Event Object-Type. - */ - protected function get_type() { - return 'Event'; - } -``` ####