MDL-83519: Docs for shortlinks

Author: davewoloszyn

docs/apis/subsystems/routing/shortlinks.md

@@ -0,0 +1,106 @@
+---
+title: Shortlinks
+tags:
+ - Short link
+ - Routing
+---
+
+<!-- cspell:ignore shortlink -->
+<!-- cspell:ignore shortlinks -->
+<!-- cspell:ignore ALPHANUMEXT -->
+
+Shortlinks are concise URLs that route to a fully-qualified URL in Moodle. Comprising of a smaller set of characters, their use is suitable for SMS, convenience, or where a longer URL would not be suitable.
+
+## Requirements
+
+Shortlinks require Moodle's routing system to be enabled and fully functioning as they have been fully integrated into the existing routing subsystem. Ensure routing is configured by following this [routing guide](https://docs.moodle.org/500/en/Configuring_the_Router).
+
+## URL structure
+
+A shortlink URL will be comprised of the following:
+
+- Base domain
+- Route group of `s` or `p`
+- Shortcode (e.g. `X8fG56aa`)
+
+A complete shortlink will look something like this: `http://yourmoodle.com/s/X8fG56aa`.
+
+## Short codes
+
+Short codes are unique identifiers at the end of a shortlink. The characters available for building short codes is limited to the extended alpha-numeric set (ALPHANUMEXT) with the the omission of ambiguous characters (i.e. upper case 'i' and lower case 'L').
+
+## Generating shortlinks
+
+Before a shortlink can be used, a shortlink will need to be generated. Shortlink generation is random and length can be specified when calling the relevant method.
+
+There are two types of shortlinks:
+
+- Public shortlinks
+- Private shortlinks
+
+### Public
+
+Public shortlinks can be accessed by anyone. Their use will be designated with a `/p/` in the URL.
+
+```php
+$public = \core\di::get(\core\shortlink::class)->create_shortlink(
+    component: $component,
+    linktype: $linktype,
+    identifier: $identifier,
+    userid: 0,
+    minlength: 4,
+    maxlength: 4,
+);
+```
+
+### Private
+
+Private shortlinks are tied to a specific user or set of users. Their use will be designated with a `/s/` in the URL.
+
+```php
+$private = \core\di::get(\core\shortlink::class)->create_shortlink_for_users(
+    component: $component,
+    linktype: $linktype,
+    identifier: $identifier,
+    userids: $userids,
+    minlength: 4,
+    maxlength: 4,
+);
+```
+
+## Using shortlinks
+
+Each component using shortlinks will need to have a `shortlink_handler` class. There are two methods that the implemented interface requires:
+
+- `get_valid_linktypes()`
+- `process_shortlink()`
+
+```php
+class shortlink_handler implements shortlink_handler_interface {
+    #[\Override]
+    public function get_valid_linktypes(): array {
+        return [
+            'view',
+        ];
+    }
+
+    #[\Override]
+    public function process_shortlink(
+        string $type,
+        string $identifier,
+    ): ?\core\url {
+        return match ($type) {
+            'view' => new \core\url('/mod/assign/view.php', [
+                'id' => $identifier,
+            ]),
+            default => null,
+        };
+    }
+}
+```
+
+Assuming the shortlink has been generated, the above example would allow a shortlink URL of `http://yourmoodle.com/s/SHORTCODE` to map to `http://yourmoodle.com/mod/assign/view.php?id=IDENTIFIER`
+
+## See also
+
+- [Routing](../routing/index.md)