So you want to make a Jellyfin plugin

Awesome! This guide is for you. Jellyfin plugins are written using the dotnet standard framework. What that means is you can write them in any language that implements the CLI or the DLI and can compile to net6.0. The examples on this page are in C# because that is what most of Jellyfin is written in, but F#, Visual Basic, and IronPython should all be compatible once compiled.

0. Things you need to get started

Dotnet SDK 6.0
An editor of your choice. Some free choices are:

Visual Studio Code

Visual Studio Community Edition

Mono Develop

0.5. Quickstarts

We have a number of quickstart options available to speed you along the way.

Download the Example Plugin Project from this repository, open it in your IDE and go to step 3
Install our dotnet template by downloading the dotnet-template/content folder from this repo or off of Nuget (Coming soon)
```
dotnet new -i /path/to/templatefolder
```

Run this command then skip to step 4

   dotnet new Jellyfin-plugin -name MyPlugin

If you'd rather start from scratch keep going on to step one. This assumes no specific editor or IDE and requires only the command line with dotnet in the path.

1. Initialize Your Project

Make a new dotnet standard project with the following command, it will make a directory for itself.

dotnet new classlib -f net6.0 -n MyJellyfinPlugin

Now add the Jellyfin shared libraries.

dotnet add package Jellyfin.Model
dotnet add package Jellyfin.Controller

You have an autogenerated Class1.cs file. You won't be needing this, so go ahead and delete it.

2. Set Up the Basics

There are a few mandatory classes you'll need for a plugin so we need to make them.

PluginConfiguration

You can call it whatever you'd like really. This class is used to hold settings your plugin might need. We can leave it empty for now. This class should inherit from MediaBrowser.Model.Plugins.BasePluginConfiguration

Plugin

This is the main class for your plugin. It will define your name, version and Id. It should inherit from MediaBrowser.Common.Plugins.BasePlugin<PluginConfiguration>

Note: If you called your PluginConfiguration class something different, you need to put that between the <>

Implement Required Properties

The Plugin class needs a few properties implemented before it can work correctly.

It needs an override on ID, an override on Name, and a constructor that follows a specific model. To get started you can use the following section.

public Plugin(IApplicationPaths applicationPaths, IXmlSerializer xmlSerializer) : base(applicationPaths, xmlSerializer){}
public override string Name => throw new System.NotImplementedException();
public override Guid Id => Guid.Parse("");

3. Customize Plugin Information

You need to populate some of your plugin's information. Go ahead a put in a string of the Name you've overridden name, and generate a GUID

Windows Users: you can use the Powershell command New-Guid, [guid]::NewGuid() or the Visual Studio GUID generator

Linux and OS X Users: you can use the Powershell Core command New-Guid or this command from your shell of choice:

od -x /dev/urandom | head -1 | awk '{OFS="-"; srand($6); sub(/./,"4",$5); sub(/./,substr("89ab",rand()*4,1),$6); print $2$3,$4,$5,$6,$7$8$9}'

uuidgen

Place that guid inside the Guid.Parse("") quotes to define your plugin's ID.

4. Adding Functionality

Congratulations, you now have everything you need for a perfectly functional functionless Jellyfin plugin! You can try it out right now if you'd like by compiling it, then placing the dll you generate in the plugins folder under your Jellyfin config directory. If you want to try and hook it up to a debugger make sure you copy the generated PDB file alongside it.

Most people aren't satisfied with just having an entry in a menu for their plugin, most people want to have some functionality, so lets look at how to add it.

4a. Implement Interfaces

If the functionality you are trying to add is functionality related to something that Jellyfin has an interface for you're in luck. Jellyfin uses some automatic discovery and injection to allow any interfaces you implement in your plugin to be available in Jellyfin.

Here's some interfaces you could implement for common use cases:

IAuthenticationProvider - Allows you to add an authentication provider that can authenticate a user based on a name and a password, but that doesn't expect to deal with local users.
IBaseItemComparer - Allows you to add sorting rules for dealing with media that will show up in sort menus
IIntroProvider - Allows you to play a piece of media before another piece of media (i.e. a trailer before a movie, or a network bumper before an episode of a show)
IItemResolver - Allows you to define custom media types
ILibraryPostScanTask - Allows you to define a task that fires after scanning a library
IMetadataSaver - Allows you to define a metadata standard that Jellyfin can use to write metadata
IResolverIgnoreRule - Allows you to define subpaths that are ignored by media resolvers for use with another function (i.e. you wanted to have a theme song for each tv series stored in a subfolder that could be accessed by your plugin for playback in a menu).
IScheduledTask - Allows you to create a scheduled task that will appear in the scheduled task lists on the dashboard.

There are loads of other interfaces that can be used, but you'll need to poke around the API to get some info. If you're an expert on a particular interface, you should help contribute some documentation!

4b. Use plugin aimed interfaces to add custom functionality

If your plugin doesn't fit perfectly neatly into a predefined interface, never fear, there are a set of interfaces and classes that allow your plugin to extend Jellyfin any which way you please. Here's a quick overview on how to use them

IPluginConfigurationPage - Allows you to have a plugin config page on the dashboard. If you used one of the quickstart example projects, a premade page with some useful components to work with has been created for you! If not you can check out this guide here for how to whip one up.
IServerEntryPoint - Allows you to run code at server startup that will stay in memory. You can make as many of these as you need and it is wildly useful for loading configs or persisting state. Be aware that your main plugin class (IBasePlugin) cannot also be a IServerEntryPoint.
BaseController - Allows you to define custom REST-API endpoints. This is the default ASP.NET Web-API controller. You can use it exactly as you would in a normal Web-API project. Learn more about it here.

Likewise you might need to get data and services from the Jellyfin core, Jellyfin provides a number of interfaces you can add as parameters to your plugin constructor which are then made available in your project (you can see the 2 mandatory ones that are needed by the plugin system in the constructor as is).

IBlurayExaminer - Allows you to examine blu-ray folders
IDtoService - Allows you to create data transport objects, presumably to send to other plugins or to the core
ILibraryManager - Allows you to directly access the media libraries without hopping through the API
ILocalizationManager - Allows you tap into the main localization engine which governs translations, rating systems, units etc...
INetworkManager - Allows you to get information about the server's networking status
IServerApplicationPaths - Allows you to get the running server's paths
IServerConfigurationManager - Allows you to write or read server configuration data into the application paths
ITaskManager - Allows you to execute and manipulate scheduled tasks
IUserManager - Allows you to retrieve user info and user library related info
IXmlSerializer - Allows you to use the main xml serializer
IZipClient - Allows you to use the core zip client for compressing and decompressing data

5. Create a Repository

See blog post

6. Set Up Debugging

Debugging can be set up by creating tasks which will be executed when running the plugin project. The specifics on setting up these tasks are not included as they may differ from IDE to IDE. The following list describes the general process:

Compile the plugin in debug mode.
Create the plugin directory if it doesn't exist.
Copy the plugin into your server's plugin directory. The server will then execute it.
Make sure to set the working directory of the program being debugged to the working directory of the Jellyfin Server.
Start the server.

Some IDEs like Visual Studio Code may need the following compile flags to compile the plugin:

dotnet build Your-Plugin.sln /property:GenerateFullPaths=true /consoleloggerparameters:NoSummary

These flags generate the full paths for file names and do not generate a summary during the build process as this may lead to duplicate errors in the problem panel of your IDE.

6.a Set Up Debugging on Visual Studio

Visual Studio allows developers to connect to other processes and debug them, setting breakpoints and inspecting the variables of the program. We can set this up following this steps: On this section we will explain how to set up our solution to enable debugging before the server starts.

Right-click on the solution, And click on Add -> Existing Project...
Locate Jellyfin executable in your installation folder and click on 'Open'. It is called Jellyfin.exe. Now The solution will have a new "Project" called Jellyfin. This is the executable, not the source code of Jellyfin.
Right-click on this new project and click on 'Set up as Startup Project'
Right-click on this new project and click on 'Properties'
Make sure that the 'Attach' parameter is set to 'No'

From now on, everytime you click on start from Visual Studio, it will start Jellyfin attached to the debugger!

The only thing left to do is to compile the project as it is specified a few lines above and you are done.

6.b Automate the Setup on Visual Studio Code

Visual Studio Code allows developers to automate the process of starting all necessary dependencies to start debugging the plugin. This guide assumes the reader is familiar with the documentation on debugging in Visual Studio Code and has read the documentation in this file. It is assumed that the Jellyfin Server has already been compiled once. However, should one desire to automatically compile the server before the start of the debugging session, this can be easily implemented, but is not further discussed here.

To automate the process, create a new launch.json file for C# projects inside the .vscode folder. The example below shows only the relevant parts of the file. Adjustments to your specific setup and operating system may be required.
```
// part of "configurations" in the launch.json file
"request": "launch",
"preLaunchTask": "build-and-copy",
"program": "${workspaceFolder}/<path to jellyfin>/bin/Debug/net6.0/jellyfin.dll",
"args": [
   //"--nowebclient"
   "--webdir",
   "<path to jellyfin-web>/dist/"
],
"cwd": "${workspaceFolder}/<path to jellyfin>",
```
The request type is specified as launch, as this launch.json file will start the Jellyfin Server process. The preLaunchTask defines a task that will run before the Jellyfin Server starts. More on this later. It is important to set the program path to the Jellyin Server program and set the current working directory (cwd) to the working directory of the Jellyfin Server. The args option allows to specify arguments to be passed to the server, e.g. whether Jellyfin should start with the web-client or without it.
Create a tasks.json file inside your .vscode folder and specify a build-and-copy task that will run in sequence order. This tasks depends on multiple other tasks and all of those other tasks can be defined as simple shell tasks that run commands like the cp command to copy a file. The sequence to run those tasks in is given below. Please note that it might be necessary to adjust the examples for your specific setup and operating system.
```
"label": "build-and-copy",
"dependsOrder": "sequence",
"dependsOn": [
      "build",
      "make-plugin-dir",
      "copy-dll",
],
```
1. A build task. This task builds the plugin without generating a summary, but with full paths for file names enabled.
```
"label": "build",
"command": "dotnet",
"type": "shell",
"args": [
   "build",
   "${workspaceFolder}/YourPlugin.sln",
   "/property:GenerateFullPaths=true",
   "/consoleloggerparameters:NoSummary"
],
"group": "build",
"presentation": {
   "reveal": "silent"
},
"problemMatcher": "$msCompile"
```
2. A tasks which creates the necessary plugin directory and a sub-folder for the specific plugin. The plugin directory is located below the data directory of the Jellyfin Server. As an example, the following path can be used for the bookshelf plugin: $HOME/.local/share/jellyfin/plugins/Bookshelf/
```
"label": "make-plugin-dir",
"type": "shell",
"command": "mkdir",
"args": [
   "-p",
   "<path to the running jellyfin, not the project cloned from git>/plugins/YourPlugin/"
]
```
3. A tasks which copies the plugin dll which has been built in step 2.1. The file is copied into it's specific plugin directory within the server's plugin directory.
```
   "label": "copy-dll",
   "type": "shell",
   "command": "cp",
   "args": [
      "./YourPlugin/bin/Debug/net6.0/YourPlugin.dll",
      "<path to the running jellyfin, not the project cloned from git>/plugins/YourPlugin/YourPlugin.dll"
   ]
```

Licensing

Licensing is a complex topic. This repository features a GPLv3 license template that can be used to provide a good default license for your plugin. You may alter this if you like, but if you do a permissive license must be chosen.

Due to how plugins in Jellyfin work, when your plugin is compiled into a binary, it will link against the various Jellyfin binary NuGet packages. These packages are licensed under the GPLv3. Thus, due to the nature and restrictions of the GPL, the binary plugin you get will also be licensed under the GPLv3.

If you accept the default GPLv3 license from this template, all will be good. However if you choose a different license, please keep this fact in mind, as it might not always be obvious that an, e.g. MIT-licensed plugin would become GPLv3 when compiled.

Please note that this also means making "proprietary", source-unavailable, or otherwise "hidden" plugins for public consumption is not permitted. To build a Jellyfin plugin for distribution to others, it must be under the GPLv3 or a permissive open-source license that can be linked against the GPLv3.

ajb142/jellyfin-hdd-space