Cloud File Systems for Media Manager

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GSoC 2017
Cloud File Systems for Media Manager
Documentation
Gsoc2016.png
Joomla! 
4.x

Introduction

Joomla! 4.x is shipped with cloud file systems for the Media Manager by default. With the previous API, creating custom file systems was a difficult task. Thanks to the new API, it's now easy to create a custom file system. If you want to use a Cloud Service with the new Media Manager, it is advised to use OAuth2.0.

This document will guide you through important steps to create your own File System Plugin to extend the Media Manager. Before proceeding, please make sure you have the basic knowledge on how to develop a plugin for Joomla. This tutorial should help.

Create your Filesystem plugin

Configuration

First of all, we need to create a filesystem plugin to extend the Media Manager. This plugin should contain some important attributes so that it can work with the Media Manager.

Make sure your plugin contains group="filesystem". So in your [plugin-name].xml, you should have:

<?xml version="1.0" encoding="utf-8"?>
<extension version="4.0" type="plugin" group="filesystem" method="upgrade">
	<name>plg_filesystem_myplugin</name>
	<author>Joomla! Project</author>
	<creationDate>April 2017</creationDate>
	<copyright>Copyright (C) 2005 - 2017 Open Source Matters. All rights reserved.</copyright>
	<license>GNU General Public License version 2 or later; see LICENSE.txt</license>
	<authorEmail>admin@joomla.org</authorEmail>
	<authorUrl>www.joomla.org</authorUrl>
	<version>__DEPLOY_VERSION__</version>
	<description>Description</description>
	<files>
		<filename plugin="myplugin">myplugin.php</filename>
		<folder>SomeFolder</folder>
	</files>
	
	<config>
		<fields name="params">
			<fieldset name="basic">
				<field
					name="display_name"
					type="text"
					label="YOUR_LABEL"
					description="YOUR_DESCRIPTION"
					default="DEFAULT_VALUE"
				/>
			</fieldset>
		</fields>
	</config>
</extension>

The display_name parameter helps the Media Manager to display the name of your File System as a root node in the File Browser. Any adapter belonging to your File System will be displayed as children under the root.

Include any required parameters you may need such as App Secret with suitable Form Fields.

Plugin Events

  • onFileSystemGetAdapters()
  • onFileSystemOAuthCallback(\Joomla\Component\Media\Administrator\Event\OAuthCallbackEvent $event)

onFileSystemGetAdapters()

Any Filesystem plugin should contain an event called onFileSystemGetAdapters() for functionality. This event should return an array of Joomla\Component\Media\Administrator\Adapter\AdapterInterface when it is called. The event is raised when you open the Media Manager. Each AdapterInterface will be mounted under the root node of your file system.

onFileSystemOAuthCallback()

This event is fired when you used Media Manager's OAuthCallbackHandler for OAuth2.0 Authorization and Authentication process described below in the document. The event is only fired on the requested plugin. So there's no need to check for $context in a typical scenario.

An example of use of the event looks like:

public function onFileSystemOAuthCallback(\Joomla\Component\Media\Administrator\Event\OAuthCallbackEvent $event)
{
	// Your context
	$context = $event->getContext();

	// Get the input
	$data = $event->getInput();

	// Your code goes here
	
	// Set result to be returned
	$result = [
		"action" => "control-panel"
	];
	
	// Pass back the result to event
	$event->setArgument('result', $result);
}

OAuthCallbackEvent contains the input forwarded to the Media Manager OAuthCallback URI. $event->getInput() returns an Input Object.

$result defines how Joomla behaves after a redirect to the callback. There are several possible solutions available:

  • action
    • close: Closes a window which is opened by a JavaScript using window.open()
    • redirect: Redirects to the page specified by the redirect_uri
    • control-panel: Redirect to the control panel
    • media-manager: Redirect to Media Manager
  • redirect_uri
    • Used with redirect action (required)
  • message
    • Message needs to be displayed after an action
  • message_type
    • warning
    • notice
    • error
    • message(or set empty)

After setting everything, set the $result argument of the $event to pass it back to the caller.

An example to display a message to user would be:

$result = [
	"action" => "media-manager",
	"message" => "Some message",
	"message-type" => "notice"
];

This will redirect to the Media Manager and raise a notice with the text in message.

This method can be typically used to obtain authorization codes for the OAuth2.0 process. In case of any error, Joomla! will fallback to the control panel adn will display an error message.

Authentication and Authorization

Joomla! 4.x advices you to use OAuth2.0 for this process. It is a common scenario that OAuth2.0 requires a redirect url to pass authentication data to the Application. This is typically done by a callback handler. For your plugin, no need to reinvent the wheel, you can use the Callback Handler of Media Manager for fulfilling the task.

All you have to do is to set the Redirect URI to following in your OAuth2.0 Provide and Implement the onFileSystemOAuthCallback(\Joomla\Component\Media\Administrator\Event\OAuthCallbackEvent $event) in your plugin.

[site-name]/administrator/index.php?option=com_media&task=plugin.oauthcallback&plugin=[your-plugin-name]

In this example: [site-name]/administrator/index.php?option=com_media&task=plugin.oauthcallback&plugin=myplugin

Now when you do a redirect from your provider once it reaches the URL provided, the Controller for Media Manager will ensure that your plugin implements onFileSystemOAuthCallback(\Joomla\Component\Media\Administrator\Event\OAuthCallbackEvent $event) before passing any data to it. If not, you will be redirected to the Control Panel with an error message.

If you have implemented all the inputs that are passed with, the Cloud Provider will be included in the $event. You can access them using $event->getInput() and treat it as an usual input to Joomla.

After you received the input, you can use it to obtain the details of your cloud service such as Access Token, Refresh Token etc.

If you want to distinguish multiple accounts, you can use Session for that.

Note: It is advised to check against CSRF token before you proceed your request. Most cloud providers support state parameter that can be used to fulfill the task.

Common Pitfalls

It is required to urlencode() your redirect uri when you're sending it to the cloud provider. Please use it to avoid misbehaviours of your cloud.

File Serve from your Adapter

To serve your media files from the Media Manager to Joomla! Site Joomla\Component\Media\Administrator\Adapter\AdapterInterface helps you. This Interface contains a special method called getUrl($path).

$path : Path is relative to your root

The intention of the method is to provide a Public Absolute URL for the file you requested to insert in the site. For example assume your file path is /path/to/me.png in the cloud server. Now a public URL might be something like mycloud.com/share/u/myusername/path/to/me.png. How it is being served, is completely up to you. When an user wants to insert a media generated URL, this method will be used.

More details about Adapter Interface can be found in administrator/componenents/com_media/Adapter/AdapterInterface.php