[docs] Comment API

Author: ferranrecio

docs/apis/core/comment/index.md

@@ -0,0 +1,114 @@
+---
+title: Comment API
+tags:
+  - comment
+---
+
+The Comment API provides a standardized way to manage comments within Moodle. It allows developers to create, retrieve, update, and delete comments associated with various Moodle entities, such as courses, activities, and user submissions.
+
+## Usage
+
+The `\core_comment\manager` is responsible for handling all comment-related operations within Moodle. This includes rendering and managing comment data.
+
+The instantiation of the comment class is done by a single arguments object that defines the context and other relevant information for the comment being created or managed.
+
+The basic attributes for the argument object are:
+
+- `context`: the `core\context` object the comment is associated with.
+- `component`: the name of the component the comment is related to.
+- `itemid`: optional, the ID of the item the comment is associated with.
+- `area`: optional, the area the comment is associated with.
+- `cm`: optional, the `core_course\cm_info` object.
+- `course`: optional, course object (will be loaded from context if not provided).
+
+Optional attributes related to the comment area rendering:
+
+- `client_id`: a unique id to identify the comment area (it will be auto-generated if not provided).
+- `autostart`: a boolean indicating whether the comment area should be automatically expanded.
+- `showcount`: a boolean indicating whether to show the comment count.
+- `displaycancel`: a boolean indicating whether to display a cancel button.
+- `notoggle`: a boolean indicating whether to disable toggling of the comment area.
+- `linktext`: a string to indicate alternative text for the show/hide link.
+
+Once instantiated, the class provides simple methods to handle comment-related operations.
+
+## Rendering a comment area
+
+The manager class has an `output` method to get the comment area HTML. Here is a simple example of how to use it:
+
+```php
+$args = (object) [
+    'context' => \core\context\module::instance($cm->id),
+    'component' => 'mod_data',
+    'area' => 'database_entry',
+    'itemid' => $entry->id,
+    'cm' => $cm,
+];
+$comment = new \core_comment\manager($args);
+echo $comment->output();
+```
+
+Additionally, the manager class offers methods to customize the default options for the comment area:
+
+- `set_view_permission(bool $newvalue)`: Set the view permissions for the comment area.
+- `set_post_permission(bool $newvalue)`: Set the post permissions for the comment area.
+- `set_notoggle(bool $newvalue)`: Set the toggle option for the comment area.
+- `set_autostart(bool $newvalue)`: Set the autostart option for the comment area.
+- `set_displaycancel(bool $newvalue)`: Set the display cancel option for the comment area.
+- `set_displaytotalcount(bool $newvalue)`: Set the display total count option for the comment area.
+
+## Retrieving comments
+
+You can use the `get_comments()` method to fetch all comments associated with the defined context. The method has the following parameters:
+
+- `int $page`: The page number to retrieve.
+- `int $sortdirection` (default `DESC`): The sorting for the comments.
+
+The number of comments displayed per page is defined by the `$CFG->commentsperpage` configuration setting. The default value is 15.
+
+There is also a `count` method to get the total number of comments for the defined context.
+
+```php
+$comment = new \core_comment\manager($args);
+
+$count = $comment->count();
+echo get_string('totalcomments', 'mod_myplugin', $count);
+
+$comments = $comment->get_comments();
+foreach ($comments as $comment) {
+    echo $comment->content;
+}
+```
+
+## Add plugin control
+
+Similar to files, when a plugin wants to use comments it must provide a callback method to validate the comment area is correct. To do so, they must implement a callback in their `lib.php` file, specifically in the `PLUGINNAME_comment_display` function.
+
+This is an example of a possible callback for plugin `mod_myplugin`:
+
+```php
+/**
+ * Validate comment data before displaying comments
+ *
+ * @param stdClass $comment
+ * @param stdClass $args
+ * @return boolean
+ */
+function mod_myplugin_comment_display(stdClass $comments, stdClass $args): stdClass {
+    if ($args->commentarea != 'entry_comments') {
+        throw new comment_exception('invalidcommentarea');
+    }
+    if ($args->itemid != 0) {
+        throw new comment_exception('invalidcommentitemid');
+    }
+    return $comments;
+}
+```
+
+## Add and remove comments
+
+The manager class provides several methods to add and remove comments:
+
+- `add(string $content, int $format = FORMAT_MOODLE): stdClass`: Add a new comment with the given content and format.
+- `delete(int|stdClass $comment): bool`: Delete a specific comment.
+- `static delete_comments(stdClass $args): bool`: Delete all comments for the specified `context`, `itemid`, and `commentarea`.